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Approximately 99.3% of uranium on Earth is the $\mathrm{^{238}U}$ isotope, and this specific isotope has an atomic mass of $\mathrm{238.05\ u}$, where $\mathrm{u}$ is the atomic mass unit, equivalent to 1/12 the mass of a $\mathrm{^{12}C}$ atom. Including the other isotopes to obtain the average atomic mass drags the value down a little, but it still ends up ...


28

The short answer is that you can find a power-law fit ($1.61Z^{1.1}$) with low average error. I'd never really thought about it much, but after downloading the IUPAC Atomic Weights, I decided to do some curve fitting. Here's a linear fit between atomic number and atomic mass: As you say, the fit isn't very good for small $Z$, but the overall fit isn't bad ...


17

Surprisingly, I learned that there are also usages for orbitals g,h,i and even j. Actually, the letter "j" is not used, so it is s, p, d, f, g, h, i, k, l, etc. The higher angular momentum orbitals do enter the domain of science, due to excited states of atoms. Transitions to and from excited states are observable through atomic spectroscopy. For ...


16

Blocks in the periodic table should not be mixed up with groups (like noble gases). The reason why Helium is considered a noble gas is because its outermost (and at the same time only) shell is fully occupied by its 2 electrons. When you look at the electron configurations in the PTE you can see that the first element which happens to have an occupied p-...


16

Please do not underestimate the scientists of 19th century. They were as creative, intelligent and perhaps more genuinely dedicated to science than the scientists of the 21st century. Spectroscopy was the tool of the trade to identify and verify that a given substance is not a mixture. The original reference which established that Didymium was a mixture is ...


14

On the contrary, zinc(I) compounds do exist, though they are rare, and relatively unstable. Most zinc(I) compounds contain a $\ce{[Zn2]^{2+}}$ core, which is analogous to the $\ce{[Hg2]^{2+}}$ cation. The $\ce{[Zn2]^{2+}}$ ion does, however, rapidly disproportionate into zinc metal and zinc(II), and has only ever been obtained by cooling a solution of ...


14

First and foremost! Do not do this reaction unless you are properly trained and have the appropriate safety equipment. Fluorine is one of the most dangerous substances out there, and one of the presumed products, $\ce{OF2}$, is also terrifying. If you can calculate the free energy change for a reaction, you will know whether it is spontaneous. To do this, ...


13

This is an interesting question and you raise a number of points, let's step through them. A consequence of this is that relative atomic masses of elements mined—those with two or more stable isotopes—will no longer be faithful to our current periodic table. But this is already happening. $\ce{^235U}$ constitutes 0.72% of uranium found on earth and ...


13

There isn't really much sense in memorizing the periodic table. The elements you often use you will know them by heart after a while. And you can always use a table when you need it for the others. That being said if you really want to do it, mnemonics are probably the best solution to memorizing the whole table. You can find some here : https://www....


13

Periodic tables of elements (PTEs) are often abused by designers. Books are more trustworthy as long as they are written by scientists. Long story short, the second notation $(\ce{^{12}_{6}C})$ is the correct one. There is an easy to remember AZE notation: $^A_Z\ce{E}$. I suspect the PTE you were looking at lists standard (averaged) atomic weights of the ...


13

Since OP is still in the high school, I'll try to explain it simply as possible using mathematical manipulation (hoping OP is more familiar with mathematics than chemistry). Both gold and platinum consist of same crystal packing called body-centered cubic, which is illustrated in following diagram: Crystal studies of both gold and platinum has revealed ...


12

The Periodic Table arranges elements in blocks as each type of orbital fills with electrons - $s,p,d,f,g,h$. Alkali metals and alkaline earths are $s$-block filling (but could be one $s$-block slot). $p$-block six electrons to fill are trelides, tetralides, pnticides, chalcogenides, halides, inert gases (but could be one $p$-block slot). Transition metal $...


12

So if that is the case, shouldn't period 3 have more elements, since it can hold up to 18 electrons, and therefore it can have up to 18 more protons from the largest atomic number element in period 2? Indeed, elements of the same period have the same number of electron shells, but the "problem" is that in accordance with the Madelung/Janet/Klechkowski ...


12

It might be scientifically correct but it is linguistically misleading The sentence "diamond is an element" can be seen to be misleading when compared to the sentence "diamond is an allotrope of the element carbon". Or even "diamond consists of the element carbon". The issue is that clear language should distinguish between the form and the composition of ...


12

There is no theoretical limit to the number of rows, but... On one hand, as Tom Lehrer states, there may be many others but they haven't been discovard. On the other hand, after all s, p, d, f orbitals are filled in the seventh period, there might be a new row, or there might be an extension of the seventh row, as a new type of orbital (g? Anyone know it ...


11

Whatever the isotopes are for asteroidal material (and they are mostly close to those seen down here on Earth), they are contained in the 5 to 100 tons of meteoritic material that falls onto the Earth's atmosphere (and thus filters down to us on the surface) every day. It will be a long time before the cumulative pollution from asteroid (or lunar) mining can ...


11

You can memorize the periodic table in one night, simply by emulating best-practice memorization techniques and doing what memory experts do. Common sense, right? Memory experts and world champion memory ‘athletes’ activate the enormous natural power of their visual memory by using visualization and association mnemonic techniques. That’s a fancy way of ...


11

In 1978, the IUPAC Commission on the Nomenclature of Inorganic Chemistry decided that it would be necessary to have a systematic naming for the elements with atomic number greater than 100, even for those which had not been discovered. The recommendations are as follows: The name is derived directly from the atomic number of the element using the ...


10

Well, the first question to answer would be: where? The rarest element in the universe? the sun? in meteorites? on earth? in the ocean? in humans? We can tap in to the curated datasets provided by Mathematica to get the answer: Elements up to atomic number 98 have been found in trace quantities; however, the dataset does not contain any information about ...


10

The pattern is better expressed this way: Row 1: 2 elements Row 2: 2+6 elements Row 3: 2+6 elements Row 4: 2+6+10 elements Row 5: 2+6+10 elements Row 6: 2+6+10+14 elements Row 7: 2+6+10+14 elements The reason comes down to how the electrons fill the available energy levels. The thing that differentiates one element from another is the proton number, and ...


10

One attempt to order chemical elements was Döbereiner's system of triades, published in Annalen der Physik und Chemie, back in 1829 (doi 10.1002/andp.18290910217 with Wiley); or (open access with Gallica). Although an actual view into his paper permits the speculation he was not using the atom masses we know today; rather than using specific weight and ...


10

The letters are related to the electron orbitals, which were originally observed through spectroscopy. The lines shown in the spectroscope were named sharp, principal, diffuse and fine (or fundamental). With a strong magnetic or electrostatic field, these separate into one, three, five or seven lines, or energy levels. There can be up to two electrons (with ...


10

There isn't a standard symbol. However, if you choose these current symbols, please note that "table" should be placed in upright font, not italics: correct: G_{\text{table}} $G_{\text{table}}$ wrong: G_{table} $G_{table}$ The reason is because "table" is a plain old English word. You can see Which symbols are written in roman (upright) ...


8

Because if you put lanthanides and actinides in to the Periodic Table like transition metals, the table will be way too wide.


8

One use of orbitals beyond f is in computational chemistry to construct basis sets. It's important to remember that orbitals are entirely a mathmatical construct that chemists and physicists have found useful in conceptualizing chemical properties and so we can use the idea of orbitals outside of their normal context of framing the periodic table. To develop ...


8

The IUPAC periodic table (2016-pdf) is good because it quantifies the accuracy of the natural abundance atomic weights, but it doesn't give electron configuration. The NIST periodic table has electron configuration, and probably is closest to what you want. The NIST table is also good from a copyright point of view, because you can reproduce it without ...


8

Trying to learn chemistry by memorizing the periodic table is pretty superficial. I would recommend learning chemistry by doing chemical reactions. Make plastics, mix acids and bases (correctly please), ask your self why milk curdles, try to light water on fire and then ask yourself why it doesn't work even though it is made of hydrogen and oxygen. Look ...


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