Smallest particle still characterizing a chemical element. It consists of a nucleus of a positive charge, carrying almost all its mass and electrons determining its size. This tag should be applied to questions that specifically concern these particles and their properties.

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A Question About the Signs of the Exchange and Correlation Potentials

The exchange and correlation potentials refer to those defined in density functional theory. (See also http://en.wikipedia.org/wiki/Local-density_approximation) Define the exchange potential as ...
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Electron Configuration of an element with no. of electrons > 18

Let's say that we have an element, say $\ce{Ca}$. According to law, the last shell should contain only upto 8 e-. Hence, electronic configuration of $\ce{Ca}$ would be 2,8,8,2. But, according to the ...
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Molecular Assembly Program

I'm not totally sure which Stack Exchange community this would go in, but Chemistry seemed best. I've been thinking for a long time now, that it would be cool to have a program where you could design ...
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Is the atom the smallest particle, which takes part in chemical reactions?

According to modern atomic theory, the atom is the smallest particle which can take part in a chemical reaction. But during the formation of hydronium ion, $\ce{H+}$ ion reacts with $\ce{H2O}$ to form ...
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Why do no known atoms have electrons in the g or h subshells?

I'm learning about orbital quantum numbers. While checking several elements on the periodic table I noticed that there aren't any atoms that have electrons in the g or h sub-orbitals. Why is this?
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Atomic mass ratios - Is the problem providing enough info?

1 gram of Hydrogen reacts with exactly (almost) 8 grams of oxygen to produce $\ce{H2O}$. 1 gram of Hydrogen reacts with 16 grams of Oxygen to produce $\ce{H2O2}$ can ratio $m_O/m_H$ be determined from ...
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“Editing” atom nucleus

First of all. I am really bad at chemistry and all that. So this might or more likely will sound at least primitive... But this question has been bothering me for far too long. So, I was reading about ...
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How are atoms manipulated?

I was wondering how scientists are able to handle atoms. They are very small, but surely people are able to interact with them somehow? The Large Hadron Collider is one example. Also, they try and ...
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Why does ionization violate the stable or lowest energy rule in atoms?

Electrons that fill orbitals always do so in such a way that the resulting structure has the lowest energy state possible, though there are anomalies like chromium and so on. But ionization no ...
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Temperature of an atom

I read somewhere that the temperature of an atom is not defined. The definition of temperature is only for larger systems. Why is this so?
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Why neutrons are neutral?

If electrons have a negative charge and protons have a positive charge then how come neutrons have zero charge without consisting of protons and electrons ? (Excuse my bad English)
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How are nuclei stable?

We all know that the density of the nucleus is very high. Nuclei are made up of protons and neutrons, and while protons have the same charge, they are closely packed in a nucleus. How does the ...
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Electronegativity and HCl and HF molecules

In a book I am reading, it is said In the $\ce{HCl}$ molecule, the shared pair of electrons spend more time nearer the chlorine atom. In the $\ce{HF}$ molecule, the shared electrons spend more ...
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Would there be a difference if deuterium is embedded instead of protium (regular hydrogen) in acids?

So instead of regular hydrogen, it would be a deuterium (still a Hydrogen). For example, instead of $\ce{HCl}$ it would be $\ce{DCl}$ where D is a deuterium.
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Why is O2 enough to form a mole of Oxygen? [closed]

I understand that this is the most basic knowledge of moles, however I'm still unsure - according to easy research, $\ce{O2}$ forms a mole of Oxygen. As a mole is $6.022*10^{23}$, exactly what on the ...
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electron affinity and electron gain enthalpy

Can anyone help me to clarify the difference between electron affinity and electron gain enthalpy? For example- Why is second electron affinity of oxygen greater than that of sulphur? I think it ...
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290 views

It is said that atoms cannot be created. If so, then how did atoms get created after the Big Bang? [closed]

I read somewhere that atoms cannot be created. If this is true, then how did the atoms form after the Big Bang? Also, does this mean that the number of atoms in our universe has remained the same ...
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Why should the redox reaction happen between the copper ions and iron atoms?

I know that when $Cu$$^+$$^2$ ions react to $Fe$ atoms, it becomes $Cu$ + $Fe$$^+$$^2$. My question is, why? Copper atoms normally have 29 electrons. These means that in the K-shell there are 2 ...
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Why was atomic mass scale changed from Oxygen - 16 to Carbon - 12?

Why was unified atomic mass scale introduced and why was Oxygen - 16 replaced by carbon - 12 for standardizing atomic scale?
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How was the diatomic nature of many common gaseous elements originally determined?

How did scientists find out that $\ce{Cl2, H2, O2}$ atoms have a two-atomic molecular structure ?
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First ionization energy of hydrogen molecule

If we have the dissociation's energies of hydrogen molecule $H_{2}$($D_{0}$) and the corresponding molecule ion $H_{2}^{+}$ ($D_{1}$) together with the first energy of ionization of hydrogen atom ...
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Is it likely that increased understanding of quantum physics will change our understanding of chemistry?

Reading that the large hadron collider will be up and running with twice as much energy in March 2015, I was curious whether our understanding of subatomic particles has changed our understanding of ...
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Why six C atoms are usually seen in cyclic compounds?

When it gets to Carbon-based molecules, one very possible structure when there are more than six C atoms is the hexagon; though not mostly perfect, it emphasizes that six Carbon atoms tend to bond ...
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What do atoms look like?

A professor of mine noted that when he was in school, microscopes weren't powerful enough to resolve certain things (I forgot what it was). But current microscopes are powerful enough. Extrapolating ...
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What is the reason behind choosing the specific elements used for the synthesis of heavier elements?

Attempts to synthesize still undiscovered elements This is derived from the wiki page: "extended periodic table" and is one of the many examples d or f block elements are used in ...
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What defines an element's taste?

A useful post by @Martin indicated that probably the naming of Sweetwater town is because of the sweet tasting lead compounds in it's water. Then my question arose. I know that the taste of any ...
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DFT Calculations, Atomic Ionization Potentials — Which Exchange-Correlation Functional to Use, to Preserve Koopmans Theorem?

I have a program which can perform density-functional calculations for atoms, given a density functional. Of course the simplest form of exchange potential to use is one relevant for a uniform ...
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217 views

Why is Graphene So Strong?

There has been a lot of news about Graphene since its discovery in 2004. And as we are all told it is a revolutionary material which is very strong, conductive and transparent; even in some cases it ...
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Which sample contains the greatest number of atoms?

Which has the greatest number of atoms from the following samples, given 1 gram of each: 1) sodium phosphate ($\ce{Na3PO4}$) (MM : 163.94) 2) sodium phosphide ($\ce{Na3P}$) (MM:99.94) 3) potassium ...
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Does radioactivity affect chemical reactions

Do compounds of radioactive elements show a bit different behaviour, and what happens when the radioactive part of the given compound decays, e.g, Radium Chloride, what happens to it when radium ...
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Does STED microscopy allow us to see reactions happening on a substrate

This years nobel prize for chemistry went to nanoscopy using STED as a control mechanism. I have seen the atoms/molecules of a lattice vibrating as shown by Stefan W Hell in a presentation at some ...
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If radium has such a long half-life, how can radon possibly be a threat to us?

If the probability is so low that a radium atom will decay into radon at any given time (the half-life is over 1600 years), then there will be a low amount of radon produced, granted it will be ...
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Why is water transparent?

Some substances like Copper Sulfate for example have vivid colors. But why is water transparent? Does it not emit any visual light from the electromagnetic spectrum?
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definition of relative atomic mass

I found out there are 2 definitions of relative atomic mass. First definition is Ar is the mass of 1 atom of an element relative to 1/12 the mass of carbon-12 atom. It can be found in any chemistry ...
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Which group does germanium belong to?

$\mathrm{Z= 32}$ $\mathrm{1s^2\ 2s^2p^6\ 3s^2p^6d^{10}\ 4s^2p^2}$ According to me it belongs the $\mathrm{IV\ B}$ group since it has the $\mathrm{d}$ completed, but it belongs to $\mathrm{IV\ A}$. ...
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How can we confirm the number of protons in an atom?

The periodic table tells us that there are 6 protons in a carbon atom. Is there a way to verify this first-hand? Or are we just expected to believe it unquestioned?
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How to interpret a luminescence intensity vs wavelength graph?

Luminescence is defined as the amount of light emitted by a atom. But what confounds me of this graph is the fact that all the peaks are of the same height. In addition, there are no peaks in ...
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Why do principal energy levels in an atom get closer together as n increases?

The title says it all. Reasons that I can supply include: increased nuclear charge increasingly catches up in terms of influence to the increasing shielding and proof by contradiction in that if the ...
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Why is Electrostatic Potential Energy positive when the charges are like?

We know that in an atom charge of an electron at infinity is zero. As it approaches the nucleus it become more and more negatively charged. We also know that E.P.E is positive when charges are like ...
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How does the radial distribution function of Vanadium differ from that of Calcium and how does this affect the ionic electron configurations?

When Vanadium is ionised it loses the 4s electron first, meaning that it's 3+ ion has a different electron configuration to Calcium despite it being isoelectronic. Can it be explained in terms of ...
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Using knowledge of radial distribution functions, how is it possible to explain the different electron configurations of V3+ and Calcium [duplicate]

I recognize that the 3d orbital decreases in energy to lower than the 4s once it becomes occupied (even if I don't completely understand why?!). However, how is the difference in electron ...
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Why are all the orbitals that have the same principal number in Hydrogen degenerate?

In hydrogen, all orbitals with the same principal quantum number 'n' (1,2,3...) are degenerate, regardless of the orbital angular momentum quantum number'l' (0,1...n-1 or s,p,d..). However, in atoms ...
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Doubt on Photoelectric effect

In the experiment to conduct photoelectric effect a clean metal was irradiated by monochromatic light of proper frequency, electrons are emitted. Why was monochromatic light used in the experiment? ...
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Are the rules proposed by slater for the calculation of Z effective right?

Today, I studied Slater's rules for calculating the effective nuclear charge. But, one particular line " The shielding power of the d and f orbital is lesser in comparison to the p and s orbitals" ...
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What holds atoms together?

1.I know atoms are held together by Ionic and Covalent bonds and i understand the ionically bonded atoms are held together by electrostatic forces. What about covalent bonds? 2.How are molecules of ...
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55 views

What is the structure of the Nucleus? [closed]

The structure of an atom is well known to me as something like this: But what is the accurate structure of the Nucleus ? What is the arrangement of the Protons and the Neutrons or any of the other ...
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Conversion of one atom to another to get the element of the latter atom in abundance

One child who is in 9th standard has claimed to have find a solution to all practical physical problems. On asking for details, he said that all periodic elements has common components, i.e. ...
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Can the electron configuration of Te be written that way?

Normally, the electron configuration of Te is known as: $$\begin{aligned} {[Kr]} 5s^2 \ce{4d^10} 5p^4 \end{aligned}$$ Then, one day I was asked in a exam if this can be written also as: ...
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An atom of silicon in its ground state has how many electrons with quantum number l = 1?

I was solving practice problems for electron configuration and periodic table, and I got stuck through a question: An atom of silicon in its ground state has how many electrons with quantum number l ...
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Why do atoms “want” to have a full outer shell?

Okay, so I know that this is about filling the orbitals of the atom, and I understand that. What I don't understand is why? For example, an Oxygen atom has 8 protons and 8 electrons spinning around ...