Periodic Table of the Elements
Seekers of ye knowledge. Behold! The periodic table. Go now and use it wisely.
Are you still here? Well, I guess I should tell you something about the periodic table like how to read it.
Each element name is represented by an element symbol. It could be
This last convention arose during the Transfermium Wars of the late 20th century, which, despite sounding like a science fiction battle for supremacy of the galaxy, was actually nothing more than an academic argument. At this time, nuclear chemists in the United States and the Soviet Union were synthesizing elements heavier than fermium (thus the adjective "transfermium") and the governments of the United States and the Soviet Union were embroiled in the Cold War (thus the noun "wars"). Put the two together and you get Transfermium Wars a bunch of chemists arguing about whose laboratory (and by proxy, whose superpower nation) was the best.
Naming rights go to the lab with priority in a discovery. The International Union of Pure and Applied Chemistry (IUPAC), which establishes rules for things like naming chemical elements, invented systematic names to impose a kind of armistice on warring chemists. Naming elements is a much slower process now as a result. This gives the scientific community time to verify claims of discovery. If laboratory A says it's found a way to synthesize element X and laboratories B and C can't synthesize element X using the same process, no one gets to name an element that day. As a pleasant side effect, the systematic naming convention also makes it possible to name elements that haven't been synthesized yet (and even those that may never be synthesized). I can fill my periodic table with placeholder names and symbols and then replace them with real names and symbols as reality reveals itself to science.
Two numbers are usually added to each cell.6C12.011atomicnumberatomicmass
The atomic number is the number of protons inside the nucleus of an atom. It is represented by the symbol Z in equations because Z is the first letter in the word atomic number (definitely not true). Each element can be identified from this number alone. It is always a whole number greater than zero when used to identify an element. The atomic number can also be applied to things like electrons and isolated neutrons in nuclear reactions. In these situations, electrons get Z=1 and neutrons get Z=0. This topic is discussed across several sections of this book.
The atomic mass is the mass of the average nucleus in an element and is stated in atomic mass units (1u=1.6605×1027kg). It is represented by the symbol A in equations because A is the first letter in the word atomic mass (probably true, but who knows). This number is roughly equal to the total number of protons and neutrons in the typical nucleus of an element. By definition, this number is exactly equal to the number of protons and neutrons in the nucleus of your garden variety carbon atom carbon12 as it's called, which has a nucleus with 6 protons and 6 neutrons and a mass of exactly 12u. Real carbon is a blend of isotopes, nuclei of the same element with different numbers of neutrons. Your typical collection of carbon atoms is 98.9% carbon12 with 6 neutrons and a mass of 12u (by definition), 1.1% carbon13 with 7 neutrons and a mass of 13.00335u (measured), and a minute but detectable trace of carbon14 with 8 neutrons and a mass of 14.003241u (measured). This averages out to 12.011u for carbon on the Earth taken from non-living (or never alive) sources. Because living things prefer the lighter forms of carbon, the average is slightly lower than this in living and dead plants and animals. Then there's carbon on other planets, and other solar systems, and other galaxies, and other times in the history of the universe. The blend of isotopes in a sample of any element tells you something about where and when that sample came from and what kind of experiences it's had. This is what makes isotopes a subject of study unto itself.94Pu(244)atomicnumbermassnumber
Values in parentheses are used for radioactive elements whose atomic weights cannot be determined without knowing the origin of the element. The value given is the mass number of the most stable isotope of that element. The mass number is the number of protons and neutrons present in one nucleus. It is always a whole number. Elements of this type are formed in one of two basic ways naturally or artificially. (More on this later.)138Uto(???)predictedatomicnumberunknownmassnumber
Some elements have never been produced in Earthly experiments and no evidence for them exists on or off the Earth. These undiscovered elements are purely hypothetical. The tradition in this case (a tradition I invented right now) is to write the atomic number, followed by the systematic name, followed by three question marks in parentheses. I don't put a border around the cell and I use a faint gray that makes the text nearly invisible. When the discovery of a new element is announced, I'll add a border, change the text color to black, and replace the three question marks with the reported mass number.
The general layout of the periodic table is four different blocks of cells; inexplicably labeled s, p, d, and f. The names come from the obscure terminology of 19th century spectroscopy: sharp, principal, diffuse, and fine (or fundamental). Make sense now?
The cells are numbered consecutively starting at hydrogen on the upper left and continuing down and across in order of atomic number. There are two peculiarities about the table arranged this way.
Helium (He) is in the sblock, but its placed like a shampoo horn on top of the pblock. That's because the chemistry of helium is more like neon (Ne), argon (Ar), etc. the noble gases. In terms of electronic structure, which is what the blocks really relate to (see the section on orbitals below), helium definitely belongs with beryllium (Be), magnesium (Mg), etc. I guess the periodic table is chemistry's baby. The chemists get to decide how to raise it. Let's see how they do.
There is a discontinuity in the sequence after barium (Ba) and radium (Ra) atomic numbers 56 and 88, respectively. That's where the fblock should go, but it doesn't have to. The fblock is pulled out and placed below the rest of the elements. It's a formatting convention that works well for pieces of paper bound into books (and by extension, displays on book shaped electronic devices). This is something like maps of the United States with Alaska and Hawaii placed below the 48 contiguous states. It uses the space more wisely without losing much of the meaning.
Each block is double an odd number of cells wide (2, 6, 10, 14). The Austrian physicist Erwin Schrödinger explained the mathematical origin of this pattern in 1926. More on that later. For now realize that the chemical behavior of the elements are related in a way that can be derived mathematically from physical principles. Chemistry detected the patterns. Physics explained them.
Elements in the same column or group on the periodic table have similar or related chemical properties. This kind of behavior is probably best illustrated through the law of definite proportions. I don't know how to say what this law is in a sentence, so let me illustrate through examples. (The actual law of definite proportions is stated in terms of masses, but I will use the much simpler notion of "parts", where a "one part" is an arbitrary number of atoms, "two parts" is twice as many, and so on.)
Everybody knows this molecular formula.
It says if you want to make water, you take 2 parts hydrogen and 1 part oxygen and then get them to do their thing (try adding some heat). Then hydrogen (H2) plus oxygen (O) equals water (H2O). That's maybe not the best example for a book written for people who want to learn physics instead of chemistry. It's actually 2 parts hydrogen (2H2) and 1 part oxygen (O2) produce 1 part water (H2O).
What if I took 3 parts of hydrogen and added it to one part of oxygen? Could I make H3O? Would this super water give me super powers? That would be awesome. Let's see.
Crap. My extra hydrogens did nothing but stay hydrogens. Super water and super powers will have to wait. It appears that atoms only combine in definite proportions not in whatever proportion I feel like. Such are the laws of nature.
Let's try some examples that see how the law of definite proportions reveals itself in the groups of the periodic table. Take two elements from the first column on the periodic table (group 1), sodium and potassium, and one from the second to last column (group 17), chlorine. The natural way to combine these elements turns out to be one sodium atom (Na) for every one chlorine atom (Cl). That gives us sodium chloride, which we write it like this
Similarly one part potassium (K) will combine with one part chlorine (Cl) to form potassium chloride.
Elements selected from group 1 combine with those in group 17 in a similar proportion (1:1).
Let's change things up and try it again. Take two elements from the second column (group 2), magnesium and calcium, and one element from the second to last column (group 17), chlorine again. Magnesium chloride is a compound that has one magnesium atom (Mg) for every two chlorine atoms (Cl2).
Compare that to calcium chloride, which is made from one calcium atom (Ca) and two chlorine atoms (Cl2).
Elements selected from group 2 combine with those in group 17 in a similar proportion (1:2).
groups with trivial names
In general, elements in the same group on the periodic table have similar chemical behavior. There are 18 numbered groups. The 14 groups of the f block (the two separated rows near the bottom) are not numbered. Groups can be identified by the topmost element in a systematic fashion. Some of them are also known by nonsystematic, trivial names. The trivial names for groups (and periods, discussed next) seem seem anachronistic relics of some obscure forgotten age.Group 1, the lithium group, a.k.a. the alkali metalsLithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs) are all shiny, soft, highly reactive metals that are normally found attached to elements from the opposite side of the periodic table to form salts. The salt used in cooking is sodium chloride (NaCl) also known as table salt. The related compound potassium chloride (KCl) is sometimes used as a salt substitute by people on low sodium diets. Lithium chloride (LiC) was also used as a salt substitute for a while until it was found to be toxic. Hydrogen (H) may be a group1 element, but it's not an alkali metal. If you decided to by some hydrogen right now, it'd be delivered to you as a diatomic molecular gas (H2) in a pressurized tank not as a lump of shiny, soft, highly reactive metal nor attached to chlorine as a salt. When hydrogen gets together with chlorine you get hydrogen chloride (HCl), which seems superficially similar to table salt (NaCl), salt substitute (KCl), and toxic salt substitute (LiCl) except for the fact that it's a gas, not a salt. Bubble hydrogen chloride gas in water and you get hydrochloric acid. Hydrogen is an oddball in the periodic table. Where does it really belong?Group 2, the beryllium group, a.k.a. the alkali earth metalsCalcium (Ca) is an important element in your bones. Strontium (Sr) is a significant component of the radioactive fallout from nuclear weapons. Both are group 2 elements. That means that strontium from nuclear fallout can easily replace calcium in your bones and nerves. This is bad news for everyone who lived through the bad old days of regular nuclear explosions. (Your humble author was an infant back in the day when nuclear weapons were tested every two to three days on average somewhere on Earth. Thankfully, it did not kill him.) The strontium in fallout is radioactive. It is quietly carried on the winds until some of it settles on agricultural land. The strontium is absorbed by crops, which are then eaten by people. Some of it lands on pasture where it is absorbed by grass, which is eaten by livestock, which is eaten by people. Voila! Steak frites avec strontium. Strontium is nearly indistinguishable from calcium chemically, so your digestive tract extracts the radioactive strontium as if it was highly valuable calcium. Now the strontium is a part of you. Bon appétit!Group 11, the copper groupCopper (Cu), silver (Ag), and gold (Au) are the best conductors of heat and electricity. They are all group 11 elements. Nothing else needs to be said.Group 16, the carbon groupCarbon (C) is a key element to life on Earth. The adjective "organic" in chemistry refers to any molecule that contains at least one carbon atom. Living things are nothing but bags of water mixed with organic molecules (and some mineral salts). Since silicon (Si) is directly below carbon in group 16 on the periodic table, silicon based life is an interesting possibility if not on Earth, then perhaps somewhere in outer space. Unfortunately, silicon is not as reactive as carbon. When silicon does get together with another element, it tends to be oxygen. Silicon is the second most abundant element in the Earth's crust. The first is oxygen. What? Oxygen in the Earth's crust? Surely that's a mistake. I don't recall being able to breathe rocks. Oxygen is found in the Earth's crust bound to silicon to make silicon dioxide (SiO2) also known as quartz, also known as what sand is, also known as what nearly every rock on the planet is made from. Carbon is the fifteenth most abundant element in the Earth's crust. Even titanium is more abundant (ninth) and chances are good most people on Earth have never touched a piece of titanium. Carbon is easy to find. It's called charcoal. Fossilized carbon is called coal. If life could have been made from silicon, why isn't it? While silicon likes to bond with oxygen and not much else, carbon likes to bond with nearly everything. If silicon is monogamous, carbon is promiscuous. It'll hook up with anyone, anytime, anywhere. Large silicon molecules tend to be monotonous, repeating units like SiO2, SiO2, SiO2, over and over again. Carbon is much more creative single bonds, double bonds, triple bonds; bind to oxygen, bind to nitrogen, bind to more carbon. Life arose out of carbon because carbon chemistry is more versatile and thus more adaptable. Silicon based life isn't impossible, and some have proposed that silicon clays may have been the first lifeforms, but life built on carbon will surely prevail.Group 17, the fluorine group, a.k.a. the halogensThe elements in group17 are often the second element in salts. They are also known as the halogens from the Greek άλας (alas), salt and γεννω (genno), born. Like an elemental mother, the halogens "give birth to salt", but like a fairytale stepmother, the elements in group 17 are wicked. Diatomic fluorine (F2) is a highly toxic pale yellow gas. Hydrofluoric (HF) acid can dissolve glass. Fluorine hates your beauty and wants to kill you. Diatomic chlorine (Cl2) is a highly toxic yellow-green gas. Chlorine compounds are added to water to kill bacteria. We call them bleaches. In small concentration, chlorine bleaches are of little concern, but in larger concentrations, bleach will kill you too. Chlorine doesn't like you any more than fluorine does. Diatomic bromine (Br2) is a fuming red-brown corrosive and toxic liquid at room temperature. It's fuming and brown. What more do you need to know? Bromine is not your friend either. Iodine (I) is necessary for life. It's the friendly member of group 17. In solid form, its dark brown. As a vapor, it's violet or purple. You eat straight iodine and your life will be short. You consume iodine in small amounts as a part of a healthy diet and your thyroid gland will be happy. Iodine is occasionally nice to humans.Group 18, the helium group, a.k.a. the neon group, a.k.a. the noble gasesEvery chemist's worst nightmare. Not because they live to see you die like the elements in group 17. Chemists dislike elements in group 18 because they're boring. They might as well not be called chemical elements. Helium (He) and neon (Ne) don't appear to participate in any chemical reactions at all. In 1962, xenon (Xe) was finally coaxed into combining with fluorine to make several compounds, most notably xenon difluoride (XeF2) and xenon tetrafluoride (XeF4). Both of these compounds are used to etch integrated circuits in semiconductor fabrication plants. (Fabs as they're called in the biz.) Combining highly corrosive fluorine with nearly inert xenon basically makes it easier to get the fluorine to go where you want it to. Then the fluorine leaps off the xenon and kicks chemical ass. Fluorine is also the only element capable of doing any chemistry with argon (Ar), krypton (Kr), and radon (Rn). The elements in group 18 are nonreactive gases. In some sense, they're like the corrosion resistant metals prized by nobility gold, platinum, and silver thus their trivial name, noble gases. Group 18 is a castle at the end of the periodic table where the noble gases exercise their rights of inertia.
In physics, a sequence of events that repeats regularly in time is called a cycle, quantities that repeat in a cyclic fashion are said to be periodic, and the time it takes for a cycle to repeat itself is called a period. In chemistry, there are sequences of chemical properties that repeat regularly in atomic number, the chemical properties that repeat this way are called periodic properties, and the set of elements needed to complete the cycle once are called a period. Each row on the periodic table corresponds to one complete period. The most obvious periodic properties are atomic radius (or volume) and ionization energy.
The elements known so far cover seven periods. More periods can be added as heavier elements are synthesized. Element 119, ununennium (Uue), will start period8 whenever it's discovered.
In physics, a period is always the same duration by definition. In chemistry, the number of elements in a period changes according to a sequence that only a mathematician could love.
Periods increase by double the sequence of odd numbers.
Assuming this trend continues, period8 would be 18 elements longer than period7
or 50 elements long.
The element at the end of that period might be number 168 unhexoctium (Uho).
I didn't write will be because the properties of elements near the end of group8 are predicted to deviate from strict periodicity. The last cell in group8 might contain element 172. My periodic table stops at element 138 because after that the sequence goes wonky. There's also some debate as to whether it's even possible to make elements heavier than this. Reserving space for them on the periodic table seems like a waste of screen real estate.
periods with trivial names
Periods aren't as interesting as groups on the periodic table. Periods 6 and 7 are just barely interesting because they contain two regions with trivial names.period6, which contains the lanthanides or lanthanoids and has some overlap with the rare earthsThis series of elements in period6 is named after its first member lanthanum (La). It includes all members of the fblock plus the first element in the dblock lutetium (Lu). There are no group numbers in the fblock. Chemical properties vary slowly within this part of period6. Because of this, lanthanides are notoriously difficult to separate from one another chemically. That wouldn't be a bad thing, except for the fact that they tend to occur in minerals together. Praseodymium (Pr) and neodymium (Nd) are a good example. 19th century chemists thought the were one element called didymium, because it appeared to be a chemical twin of lanthanum. The Greek word for twin is δίδυμο (didymo). It wasn't until 1885 that it was recognized as an alloy of two metals "praseodidymium" (leek didymium yes, that's right, leek, the vegetable) and "neodidymium" (new didymium), later shortened to praseodymium and neodymium. If didymium was a twin, it was more like a conjoined twin. The lanthanides plus scandium (Sc) and yttrium (Y) are collectively known as rare earths. Despite their name, rare earths are not all that rare on Earth. On the contrary, they're all over the place in minute amounts. It's hard to find deposits of ores rich in rare earths. Lack of economically viable sources make the rare earths rare. Also, one of them only exists as an artificial element promethium (Pm). That's truly rare.period7, which contains the actinides or actinoidsIf the lanthanides get a special name, then so should the actinides. This series of elements in period7 is named after the first element in the fblock, actinium (Ac), and extends through to the first element in the dblock, lawrencium (Lw). It includes the heaviest naturally occurring element uranium (U). The elements after uranium only exist as creatures of nuclear reactions. Only plutonium (Pu) is manufactured in any significant amount. Something like 20tonnes of the stuff are produced in nuclear reactors each year. Most of it is used as fuel. Some of it is used for weapons. Neptunium (Np) is produced at a similar rate, but that's normally as an intermediate in the production of plutonium. The next four elements in the transuranium sequence are produced in gram quantities each year americium (Am), curium (Cm), berkelium (Bk) and californium (Cf). Americium is used in some smoke detectors, which makes it the most popular (if such a word is applicable). Elements beyond that on the periodic table have no economic significance. In some cases the amount produced in laboratories isn't measured in grams, or milligrams, or even micrograms. It's measured in individual atoms.
Metals are often defined by a list of properties. Metals are said to be
Defining metals by a list of properties that some metals don't have is a sign that we have a weak definition. Defining them with properties that some nonmetals also have is another. Defining metals by their physical properties instead of their chemical properties is a sign that we've driven off the track. The periodic table is all about chemistry after all. Isn't it?
In chemistry, being a metal is all about the kind of reactions you participate in. Metals tend to give up electrons to other elements namely, nonmetals. An atom with the "incorrect" number of electrons (one for every proton) is called an ion. Atoms that have lost electrons are called cations. Atoms that have gained electrons are called anions. When they participate in chemical reactions, metals tend to form cations and nonmetals tend to form anions. The faster a metal sheds electrons, the more metallic it is. The faster a nonmetal sucks up electrons, the more nonmetallic it is. On the periodic table, the elements with the most metallic character are located on the lower left hand side (large period number and low group number).
Conversely, the elements with the least metallic character are located on the upper right hand side (small period number, large group number). All the gaseous elements are definitely nonmetals, so hydrogen is sort of on the wrong side. The noble gases (helium, neon, argon, krypton, xenon, radon) are considered the least metallic in character. This is an odd thing to say since they don't have a tendency to acquire electrons and become anions. The noble gases don't behave like metals or nonmetals. They almost completely lack any chemical behavior at all almost.
Metalloids are elements with both metallic and nonmetallic properties. An element is a metalloid if it's near the diagonal line running down and right across the pblock. What exactly chemists consider "near" is open to debate.
Silicon is shiny like a metal, but it isn't a good electrical conductor. It isn't a good insulator either. It's a semiconductor. It's kind of like a metal and kind of like a nonmetal. If I had to make a choice I'd put that one in the metalloid category. Chemists agree with me.
Carbon in the form of graphite is shiny and an excellent electrical conductor. Two things that make it seem like a metal. Carbon in the form of diamond is transparent and an electrical insulator. Two things that make is seem like a nonmetal. (Metals can never be transparent.) But it's a good conductor of heat. So it's like a metal. Sounds like carbon should be a metalloid. But it isn't. Help! I'm drowning in exceptions.
An element is a metalloid if a chemist says so.
I need a bigger box of crayons or a less complex world to live it. The chemists have gone mad. Metal character (or lack of it) is further subdivided into subcategories.
orbitals and suborbitals
This is the part of chemistry that owes its greatest debt to physics.
Use the Schrodinger equation.Eψ(r)=22ψ(r)+U(r)ψ(r)2m
whereE=the total energy of the electronr=the position of the electron relative to the nucleus (position vector)ψ(r)=the probability of finding the electron at any position (probability distribution)=h/2π a.k.a. "hbar", reduced Planck constant, Dirac constantm=the mass of the electron2=the Laplacian operator, which is the divergence of the gradient, applied to the probability distribution. Gradient is the three dimensional, vector version of slope. Divergence is a scalar measure of the spreading of a vector field; in this case. The symbol that looks like an inverted Greek letter delta () is called a del () by the way.U(r)=the electric potential energy of the electron at any position (a scalar function)
The whole thing is really the law of conservation of energy written in a new way.Eψ(r)=the total energy of the electron at any point in space22ψ(r)=2mthe kinetic energy of the electron at any point in spaceU(r)ψ(r)=the potential energy of the electron at any point in space
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Intro to Mendeleev's reasoning.
Placement errors are highlighted in red. Predictions are highlighted in yellow.
Although not the first person to try to organize the chemical elements, Dmitri Mendeleev was certainly the most successful. His table is most famous for its gaps positions were no elements were known to exist. Mendeleev predicted four new elements with definite atomic masses and chemical properties. All four were eventually discovered.
Two of these elements were next in line after aluminum and silicon in his scheme. These predicted elements should have the same chemical properties as aluminum and silicon, but be heavier. Mendeleev appropriated the Sanskrit word for one (एकं, eka) to serve as a prefix to identify these predicted elements. Thus, ekaaluminum and ekasilicon became the placeholder names to identify the first elements to follow aluminum and silicon on his newly invented periodic table. They are now known as gallium and germanium.galliumAn element fitting the description of ekaaluminum was indeed discovered by the French chemist Paul-Émile Lecoq de Boisbaudran six years later in 1875. Lecoq named the element gallium in reference to the Latin name for France Gallia. Lecoq's critics accused him of naming the element after himself (a male chicken is called le coq in French and gallus in Latin) a charge Lecoq denied.germaniumIn 1886, an element fitting the description of ekasilicon was discovered by the German chemist Clemens Winkler. He wanted to name the new element neptunium after the planet Neptune. Neptune was discovered in 1846 following a mathematical prediction based on observations of the planet Uranus. Winkler drew parallels between the 1846 prediction of a new planet and Mendeleev's 1869 prediction of a new element. The analogy would have been perfect, but another claim for a new element named neptunium was already in the works. Winkler went with the name germanium after the Latin name for Germany Germania. (The German name for Germany is Deutschland.) Did Winkler choose germanium to match Lecoq's choice of gallium eleven years earlier? I don't know, but it seems reasonable. One thing for certain he did not make a pun about his name like Lecoq was accused of doing. Winkler is a variation on an old German word for street corner or corner shop winkel. A person who ran the corner shop would have been called a winkler. The Latin word for street corner is platearum, which sounds nothing like germanium or neptunium. The neptunium Winkler knew about turned out to be an alloy of niobium and tantalum. (Oops.) The element we know as neptunium today was given its name in 1940 because it follows uranium in the modern periodic table. Uranus, Neptune, Pluto in the solar system correspond to uranium, neptunium, plutonium on the periodic table. (Please note: I don't care if Pluto is a planet or not.)
Actual scientific discovery is often a messy process. The other two question marks in Mendeleev's first periodic table were eventually replaced with the elements scandium and hafnium, but their stories go against the customary narrative arc of the scientific method predict and test, confirm or refute.scandiumMendeleev had the right idea when he devised the periodic table, but some of his data about the already known elements wasn't that great. The first draft had a pile of errors near the bottom. The masses of cerium, lanthanum, ytterbium, indium, and thorium were way off. He also had one false element in his first table didymium, which turned out to be a mix of the elements praseodymium and neodymium. Into this mess he plopped a prediction for an element with a mass of 45. An element with this mass was discovered in 1879 by the Swedish chemist Lars Fredrik Nilson, but he was unaware of Mendeleev's prediction at the time. Nilson named the new element scandium after his homeland Sweden, which lies in the cultural region of Europe known as Scandinavia (Scandia in Latin). Mendeleev named his predicted element ekaboron since he thought it would have chemical properties similar to boron's. Scandium is more like yttrium than boron, however, and the element that would be ekaboron in a modern periodic table is aluminum. To say that Mendeleev predicted the existence of scandium is weak.hafniumMendeleev's first periodic table makes a prediction for an element similar to titanium and zirconium but heavier. He should have called in ekazirconium, but he didn't. Once Mendeleev got better mass numbers, he placed lanthanum in this slot and forgot about his original prediction. This mistake wasn't corrected until 1914 when the physicistHenry Moseleyinvented the concept of atomic number and then hafnium could be discovered. Moseley and the story of hafnium will be dealt with later.
Moseley invents (or discovers) the notion of atomic number and decides to reorder the elements of the periodic table. In 1914, he predicted the existence of the elements that later came to be known as technetium (1937), promethium (1942), hafnium (1922), and rhenium (1925).
August 10, 1915: Henry G.J. Moseley Killed in Action.
Sometimes the cells are color coded depending on what aspect of each element you'd like to highlight. Here's one that shows the phase of each pure element at room temperature. I prefer red for solid, green for liquid, and blue for gas. Sometimes, these elements have never been produced in large enough quantities to determine their phase at room temperature. We can't say whether they're solid, liquid, or gas. I've got a color for this situation gray.
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The main cosmic (outside the Earth) origins of the dominant isotopes are shown in the table above (source: Samarasingha & Ivans and Johnson).
Big bang nucleosynthesis (cosmological synthesis)
Cosmic ray spallation, cosmic ray interactions with the interstellar medium, cosmic ray fission
Hydrostatic nucleosynthesis, fusion in low mass stars
Explosive nucleosynthesis, fusion in massive stars
Neutron capture nucleosynthesis, merging neutron stars, dying low mass stars (planetary nebulae)?
There are currently 118 known chemical elements. 80 of them have at least one stable isotope essentially unchanged since their formation and eternal in all ways. 38 have only unstable isotopes and are said to be radioactive they spontaneously decay into other elements by the emission of neutrons (neutron emission) or helium nuclei (alpha decay) or by the transformations of neutrons into protons (beta decay). All elements heavier than hydrogen are produced by nucleosynthesis the creation of new nuclei from the bits and pieces of preexisting ones.
The elements found on Earth that have been here since its formation 4.5 billion years ago are known as primordial elements. The light primordial elements hydrogen, helium, and lithium were all formed in the first three minutes after the big bang 13.8 billion years ago. Most of the remaining primordial elements from carbon to iron were cooked in the nuclear furnaces of stars that died sometime between the big bang and the formation of the Earth. Everything heavier than iron and any primordial element not synthesized in a working class star was formed during the last paroxysms of a supergiant star as it went supernova. Primordial elements are literally stardust.
Some elements found on Earth were not present at its formation. These trace isotopes are continually formed through naturally occurring radioactive processes, like
All 80 stable elements and 4 radioactive elements are considered primordial. Surprisingly, this includes helium (He) and argon (Ar), which are primordial in outer space, but almost entirely radiogenic on Earth. A relatively small number of primordial helium and argon atoms were certainly trapped within the Earth as it was forming. The rest of them are the decay products of other elements. The helium used in party balloons is the decay product of uranium and thorium. It collects in the same kind of rocks that hold natural gas and is separated out as a byproduct of commercial extraction. The argon used in party balloons (by people who like ballons that fall with a thud) is the decay product of radioactive potassium. 93.4% of the helium and 99.6% of the argon in and on the Earth were generated after the Earth formed.
The remaining 34 elements were discovered after they were produced synthetically. Discovered might not be the right word here, since most of these were intentional acts. Nuclear chemists had a process in mind for synthesizing the element, they did the process, and the element came out. The first of these was technetium (Tc). It was discovered in 1937 in a discarded piece of molybdenum (Mo) foil that had been exposed to radiation in an early particle accelerator called a cyclotron. The most famous synthetically produced element is probably plutonium (Pu). It was first synthesized in 1941, but its discovery was kept secret until 1946 (a year after WWII ended) so that it could be used to build the first and third atomic bombs. (The second atomic bomb used uranium.)
Of the 34 non-primordial radioactive elements, 14 were later found to exist in nature. The estimates of the abundances of these elements is astonishingly small. One kilogram (1kg) of uranium probably contains an estimated one nanogram (1ng) of technetium or plutonium. The absolute loser in this regard is astatine (At). The whole crust covering the entirety of the Earth probably contains less than one gram of astatine. Your average nucleus of astatine barely makes it to the end of a standard eight hour workday before it retires from existance forever.
The remaining 20 synthetically produced elements have never been seen in nature. Some may never be seen outside the lab. They are as close to artificial as one can get.
4 primordial radionuclidesZArelement83208.980Bibismuth90232.038Ththorium91231.035Paprotactinium92238.028Uuranium14 trace radionuclidesZAelement43(98)Tctechnetium61(145)Pmpromethium84(209)Popolonium85(210)Atastatine86(222)Rnradon87(223)Frfrancium88(226)Raradium89(227)Acactinium93(237)Npneptunium94(244)Puplutonium95(243)Amamericium96(247)Cmcurium97(247)Bkberkelium98(251)Cfcalifornium20 synthetic radionuclidesZAelement99(252)Eseinsteinium100(257)Fmfermium101(258)Mdmendelevium102(259)Nonobelium103(266)Lrlawrencium104(267)Rfrutherfordium105(268)Dbdubnium106(269)Sgseaborgium107(270)Bhbohrium108(277)Hshassium109(278)Mtmeitnerium110(281)Dsdarmstadtium111(282)Rgroentgenium112(285)Cncopernicium113(286)Nhnihonium114(289)Flflerovium115(290)Mcmoscovium116(293)Lvlivermorium117(294)Tstennessine118(294)Ogoganesson
Periodic Table of the Elements