Questions tagged [elements]

A pure chemical substance consisting of a unique type of atom with a distinguished by its atomic mass.

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Why can't elements and atoms be separated by physical and chemical means?

Our textbook tells us ''that elements and atoms cannot be separated by chemical and physical methods. He says only atoms can be separated by nuclear methods.'' First of all, I would like to start my ...
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Elements with most commonly occurring isotope being different from the most stable one

Usually, stable isotopes have highest abundances, often much higher than radioactive ones. Are there any elements having most commonly occurring isotope different from the most stable isotope?
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How was it known certain materials were elemental (Hydrogen 1766, Phosphorous 1669, ...) before Dalton showed that matter was made of atoms in 1803?

Dalton showed in 1803 that matter was made of atoms rather than continuously distributed. But phosphorous, hydrogen, and other elements were identified before this discovery. How could they have known ...
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Melting point of Scandium group elements

As I am learning about elements physical properties, i notice that the melting points of Sc, Y, La, Lu decreases down the group. I suppose the increase of atomic mass would result in better Van der ...
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Are any two elements indistinguishable by a single measure?

Elements can be investigated using a range of different techniques to determine their fundamental properties. Some properties of an element can be observed only in a collection of atoms or molecules ...
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What words can I use to differentiate between cases where two atoms are of the same element versus when two atoms are of different elements?

I am writing my thesis, and usually I'm quite good with picking the right words for specific phenomena, yet I am having trouble finding the right words for this specific circumstance. I am trying to ...
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Stability of beryllium isotopes

I have been reading about isotopes and their abundance on Wikipedia. It states that lithium has 2 stable isotopes, beryllium has 1 stable isotope (monoisotopic and mononuclidic) and boron has 2 stable ...
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Very Little Astatine

Astatine is the penultimate halogen in the periodic table with atomic number 85. It is very much radioactive and would vaporize itself by its own radioactivity before being collected. But there is ...
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Are elements made out of many atoms? [closed]

So im reading a chemistry book right now, and always thought an element is made out of ONE atom, with special properties that make it this element. Amount of Protons, neutrons and electrons. But this ...
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What parameters do you use to find the order in which elements will leave a solution during electrolysis?

I am looking to perform electrolysis on a molten solution of many elements, specifically a mix of iron, sodium, potassium, silicon, aluminum, and titanium oxides and chlorides. What I'm trying to ...
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Why are some elements diatomic under normal conditions while others are not?

I see that the the standard form of many elements are diatomic molecules under normal conditions (eg oxygen, hydrogen and iodine are usually seen as diatomic molecules) and are all among the most ...
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How many carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms are there in the observable universe?

If I could somehow reliably count all the carbon, nitrogen, hydrogen, oxygen, and phosphorus atoms in the observable universe, what number would I come up with?
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Is there an international standard for rating the danger of chemical elements?

I'm writing a small little tool (something like an interactive periodic table) and I wanted a good "guesstimate" of the danger of certain elements, to visualize across said table. I could go ...
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Is the periodic table ordered by bonded atoms and does that change the electron configurations and ordering? [closed]

In my book (Mortimer, The Basic Knowledge of Chemistry) the electron structure of the elements is introduced, there the relative energies of the atomic orbitals are shown: 1s < 2s < 2p < 3s &...
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Element Names in English [closed]

Na - Sodium - Natrium K - Potassium - Kalium W - Tungsten - Wolfram Sb - Antimony - Stibium and so forth. [English only] Why do we not use the names that match the symbols?
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Why does berkelium have two electronic configurations?

J.D. Lee Concise Inorganic Chemistry, Appendix E: Electronic Structures of the Elements [1, p. 601] provides two electronic configurations for berkelium: $$ \ce{Bk}\quad \begin{cases} [\ce{Rn}]~\...
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Transform a star's carbon and oxygen into elemental hydrogen

Forgive me if this a really dumb Question, and yesterday Star Trek: Deep Space 9 suggested a terraforming specialist might transform a star's carbon and oxygen into elemental hydrogen, no details of ...
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Can an element be a single atom or a molecule made up of atoms of the same element?

Some online websites and some books as well suggest that elements are either atoms (e.g. Ne) or molecules (e.g. $\ce{H2}$, $\ce{O2}$). Original source: Tro, Chemistry: A Molecular Approach (2008) ...
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How did we know about the existence of elements before quantum theory? [duplicate]

I'm reading a book about the elements, and it says all the time: discovered/isolated by X in a year. But how did the people know about the elements before the quantum theory? How did they know they ...
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Do chemical bonds impact half-life of elements?

Let’s say we have element X with half life of 100 years. Can chemical bonds like X−X or X−Cl increase/decrease half-life of X? As a follow up question, can it increase/decrease radioactivity of X?
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Which ionic radius is most relevant for anticipating co-crystalization?

In the context of anticipating the likeliness that elemental impurities co-crystalize into the crystals containing an element of similar radius (see this question), which is the relevant radii to ...
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Just how accurate is this XKCD comic about building a real-life periodic table with cubes made up of each element?

I was reading the book “What If?” by Randall Munroe and this part was very intriguing to me. He answered the question in the title and I was curious if his answer was realistic, and if not, which ...
user177107's user avatar
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How many elements have been identified for which there are no known spectral lines?

Background: @ProfRob's answer to If there were undiscovered elements (119 on) in a star's spectral lines, could we tell? in Physics SE begins: I think that would be very difficult indeed. ...
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How do the odd proton-number elements originate?

I have a question about the origin of the odd proton-number elements in the periodic table, please. As it is generally thought that the big bang produces hydrogen first, and then hydrogen combined to ...
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Why is Gallium-69 stable, Gallium-70 unstable and Gallium-71 stable again?

Why is gallium 70 suddenly unstable, whereas it becomes stable again when you add another neutron? Shouldn't isotopes become unstable when there are either too few or too many neutrons? Why is gallium ...
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What are the safest non-toxic elements I can own? [closed]

As in a recent question, I mentioned I collect elements. My collection already has quite a few elements and a rare alloy (I have silicon, molybdenum, tungsten, gold, platinum, silver, copper, ...
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Can osmium react with oxygen at room temperature?

I’m an avid collector of elements (I love shiny rocks - don’t judge). I’m looking to buy some osmium, as it’s one of the heaviest and hardest metals out there. However, people online told me to avoid ...
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8 votes
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Naming of the chemical elements and original sentences by the discoverers

Does anyone recall a printed or an online compilation where the names of all the chemical elements are listed along with the original sentence, from a research paper, containing the name of the ...
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Why does sulphur exist in two forms in solid state, monoclinic and rhombic? Why in one favoured over another at a certain temperature and pressure?

Both Rhombic and Monoclinic sulphur consist of $S_8$ molecules packed together. Yet the former is more stable below $114^{\circ}C$ at 1 atm and spontaneously converts to monoclinic sulphur above that ...
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The melting and boiling point decreases down the group up to group 14 (not including transition metals), but the trend reverses from group 15. Why?

In groups 1, 2, 13 and 14, the melting and boiling point decreases down the group with a few exceptions. In group 15 the melting/boiling point increases up to Arsenic and then started decreasing. In ...
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How many atoms are there in single element? [closed]

Elements are chemical substances made up of the same types of atoms (atoms with the same proton number), whereas molecules are chemical compounds made up of atoms from two or more different elements. ...
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Why is effective nuclear charge used to explain the periodicity of size of atoms and ions?

Why is effective nuclear charge used for explaining the periodicity of size of atoms and ions, even though radius depends upon many other factors? The size of $\ce{Na+}$ is smaller than that of $\ce{...
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Does the Atomic Mass listed for each element on the periodic table reflect the relative abundances of their isotopes on Earth? Or in the Universe? [duplicate]

Somehow, I cannot find a site or book or paper explaining exactly how the average atomic masses for the elements on the periodic table are weighted.... I posted a question either here or on Physics S....
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what does it mean to say oxygen in a given context?

My textbook "chemistry by Julia" says the following When it comes to expressing the molar mass of elements such as oxygen and hydrogen, we have to be careful to specify what form of the ...
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Are the names for chemical elements the same in both modern Greek and classical Greek? [closed]

Have the modern Greek names for chemical elements known during antiquity (silver, copper, mercury, lead, gold, etc.) retained their Classical Greek names, or did they adopt Latin ones, or do they ...
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1 vote
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Why are the rare Earth elements divided into light and heavy categories?

Rare Earth's up to z=62 (Samarium) are often called 'light' rare Earths, while z=63 (Europium) and beyond are sometimes referred to as 'heavy' ones. Why such distinction? I didn't have come across (or ...
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Predict the valence configuration of this element using the first five ionization energies [closed]

If the first five ionization energies of an element are, respectively: $\pu{1.09 kJ/mol}$, $\pu{2.35 kJ/mol}$, $\pu{4.62 kJ/mol}$, $\pu{6.22 kJ/mol}$ and $\pu{37.83 kJ/mol}$, to which group of the ...
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How can chlorine be 'only' the third-most electronegative element yet have the highest electron affinity?

From Wikipedia: It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the Pauling scale,...
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Oxidation number approximately

I argued with my lecturer when he is saying that during the calculation of oxidation number, and your answer give you like 3.46 you can approximate it to whole number, I know tell him NO that if the ...
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Probability of forming dihydrogen with molecular weight 3 [closed]

During a lecture, my professor told us that the probability $P$ to form a hydrogen molecule $\ce{H2}$ with mass number 3 could be calculated out of the abundances, $\gamma$, of the isotopes of this ...
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Could there ever be a way to safely handle visible amounts of elements like astatine, francium, or protactinium? [closed]

This is something I'd actually be interested in doing if possible. I've asked about artificial stability here https://physics.stackexchange.com/questions/584595/could-there-at-least-theoretically-ever-...
user17584's user avatar
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1 answer
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How would someone in 1917 describe elements 43, 61, 72, 75, 84, 85, 87, 89, and 91? [closed]

https://books.google.com/books?id=aaELAAAAYAAJ&printsec=frontcover#v=onepage&q&f=false Notice the list of elements on pages 62–63. It includes a short description of each element's "...
user17584's user avatar
8 votes
1 answer
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Which allotropes of sulfur exist naturally?

I'm writing a paper on chemistry and I would like to know which allotropes of sulfur exist naturally. I've searched on the Internet but I haven't found anything about natural sulfur allotropes except ...
Tech Expert Wizard's user avatar
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Can someone help me figure out what the noble gas configurations for zirconium and holmium are? [closed]

I am currently working on noble gas configurations in chemistry and I am having a hard time understanding why I got two questions wrong on a practice. The instructions for the practice are here: Write ...
Audrey W.'s user avatar
4 votes
2 answers
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Is there a standard scholarly reference for lattice constants of crystals of the elements?

I need to discuss the lattice constants of bulk crystals of several metal and semiconductor elements. I can find plenty of tables and numbers that are probably "close enough" but for a paper ...
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A theoretical chemistry question about elements and their presence over time [closed]

I'm not a chemist myself, but I can't think of a better place to get some insight about elements and chemistry than from people who live and breathe it here on stackexchange. This is not any kind of ...
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How do you know what elements will bond in a reaction? [closed]

I know all about the types of reactions, synthesis, decomp. etc., but when a bond is broken, how do you know that the free element will bond to another molecule? Is it because that element has a ...
Pasta Man's user avatar
16 votes
1 answer
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How did Mendeleev know elements from compounds or mixtures?

I read that Mendeleev initially thought didymium was an element, but it was actually a mixture. How did he know the rest of the chemicals in the periodic table were elements and not compounds, ...
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Chemical elements or compounds with yellowish white color [closed]

Are there chemical elements or compounds that have a yellowish white (cream) color in their natural state?
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How do scientists know they have discovered an element? [duplicate]

I have a background in math not chemistry and perhaps this question is inappropriate but I will try. I read that after pitchblende was discovered Martin Klaproth in 1879 a latter date discovered that ...
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