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.

learn more… | top users | synonyms

0
votes
0answers
4 views

Is there an algorithm for ascertaining the relative size of an atomic/ionic radius?

To the best of my knowledge, the following properties affect atomic radius. The grounded-state size of the valence electron shell. The Coulomb force of the core electrons less the Coulomb force of ...
3
votes
1answer
106 views

Why do ion cores not move in a metal?

The delocalized electrons in a metal move about because of the electrostatic attractions between them and many different positive ion cores. But why does the same not occur with the ion cores ...
1
vote
0answers
40 views

Molecules from atoms [on hold]

Why do two oxygen atoms combine to form a molecule and not 3 or 4? Also, why does one sodium and one chlorine atom combine to form $\ce{NaCl}$ while two chlorine atoms are required to combine with one ...
3
votes
1answer
50 views

Calculating edge length of a cube atom

This question comes straight from a worksheet we were assigned in chemistry, though it’s more math focused of a question I hope that this is an appropriate question to ask here. Calculate the edge ...
6
votes
1answer
61 views

Why is Astatine monoatomic?

I learnt that halogens always form covalent bonds to becoms diatomic molecules. So why is astatine monoatomic? I mean they have the same properties, why shouldn't they all be diatomic?
7
votes
1answer
519 views

Really how rare are hydrogen atoms?

Hasok Chang, a chemist, but perhaps more a philosopher recently published the book Is Water H2O? . Chang used the question and an extensive web of arguments ultimately as a platform to support a ...
1
vote
0answers
64 views

How many hydrogen atoms are in a sample of NH3?

How many hydrogen atoms are contained in 8.66 moles of $\ce{NH3}$? The answer is given after the log has been taken, so the final answer is 25.19. What I have been doing is multiplying 8.66 by 6.02 ...
2
votes
1answer
41 views

Placing the atomic mass and number of an element… [closed]

Why are the atomic and the mass numbers of an element flipped in the textbooks relative to the periodic table?
6
votes
1answer
86 views

What is there in an atom between the nucleus and electrons?

As you can see the atom consists not only of the nucleus and electron but also of "empty space is the space empty or is their something else?
2
votes
1answer
43 views

Atomic number $Z$

If electrons were spin-$\frac {3}{2}$ instead of spin-$\frac {1}{2}$ , what would be the atomic number $Z$ for the first noble gas ?
3
votes
2answers
38 views

Why does ionization energy increase as we go from left to right in a period?

Why does ionization energy increase as we go from left to right in a period? In my textbook, the explanation is as follows: "This is consistent with the idea that electrons added in the same ...
4
votes
2answers
26 views

Interaction radius of a molecule

What is the most commonly used radius of an atom or molecule to describe the area that must touch another area of another molecule for the two to react. Is there one radius that always works or does ...
4
votes
1answer
148 views

Usefulness of the outdated Bohr model?

Whilst the Bohr model is incomplete and incorrect, it had limited usage in predicting spectral lines. In the same way, could it possibly with limited accuracy, be used to predict the outcome of ...
5
votes
1answer
40 views

How was it determined that the electron observed in the cathode ray experiments was the same particle that gave an atom its balancing negative charge?

How was it determined that the electron observed in the cathode ray experiments was the same particle that gave an atom its balancing negative charge? Couldn't there have been an entirely different ...
0
votes
0answers
66 views

Diatomic Molecules/Elements

What is the difference between diatomic molecules and elements? Also, If oxygen is element of a single atom, then what makes it a diatomic element? But, then I read that a single oxygen atom can ...
5
votes
1answer
353 views

Why are so many wave functions associated with hydrogen?

According to Wikipedia, there's an infinite set of possible wavefunctions (orbitals) for the hydrogen atom: $$\psi_{n\ell m}(r,\theta,\phi) = \sqrt {{\left ( \frac{2}{n a_0} \right ...
1
vote
1answer
40 views

How do atoms combine? [closed]

Do atoms combine with the nearest atoms possible because of lower delta E (less energy needed to form a stable nucleus)?
3
votes
1answer
88 views

Are the energies of orbitals that are not filled in an atom, equal?

In a hydrogen atom only 1s orbital is filled. Does this mean that the energies of all other orbitals are equal? If so,why?
4
votes
1answer
46 views

Isn't the mass of a carbon 12 equal to a mass of 6 neutron + 6 proton + 6 electron?

The mass of Carbon 12 is 12u from definition, and is formed with 6 neutron, each with 1.0087u, 6 proton, each with 1.0072u and 6 electron, each with 0.0005u, which all add up to 12.0894u. why is there ...
5
votes
1answer
50 views

How were the absolute masses of atoms calculated before the mass spectrometers?

I understand that true (non-relative) masses of atoms are calculated with a mass spectrometer. using this relationship: Centripetal Force = Force due to magnetic field(B) But I was wondering how ...
0
votes
0answers
19 views

Correlation between crystal structure and underlying atomic properties

Can the crystal structure of an element/metal be explained by any underlying atomic or quantum mechanical properties of the element or is it an intrinsic property by itself (like atomic number)?
0
votes
1answer
73 views

Can we make Gold in a Lab? [duplicate]

Can we make Gold in a Lab? Is it possible to make changes in metals that will create Gold? and How? I have tried to search something related to this but didn't get any good results. Thanks in Advance
2
votes
2answers
37 views

Does Uranium ore count as a mixture?

I'm doing an assignment where we must research the separation of a mixture to obtain a useful final product. I thought about the separation of Uranium from its ore after it has been mined, but I did ...
5
votes
1answer
126 views

Do multielectron atoms have nodes?

For hydrogen, other than in the 1s state, the electron wavefunctions have radial and/or angular nodes where the electron probability density is zero. In helium or further atoms with more than one ...
6
votes
0answers
60 views

Density Functional Theory with Generalized Gradient Approxmations (GGA) - What Happens if the Electron Density Shows a “Kink” at the Ion Position?

My question may be stupid, so please correct me if you find anything which is obviously erroneous. In the following I will place a question mark (?) besides points/steps I consider doubtful. My ...
3
votes
0answers
27 views

Signs of 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 ...
2
votes
1answer
62 views

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 ...
2
votes
2answers
71 views

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 ...
9
votes
1answer
1k views

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 ...
3
votes
3answers
144 views

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?
1
vote
1answer
39 views

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 ...
1
vote
2answers
97 views

“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 ...
2
votes
1answer
34 views

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 ...
1
vote
1answer
20 views

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 ...
7
votes
3answers
1k views

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?
5
votes
1answer
152 views

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)
4
votes
3answers
122 views

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 ...
4
votes
1answer
182 views

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 ...
7
votes
1answer
388 views

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.
-2
votes
2answers
71 views

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 ...
1
vote
0answers
120 views

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 ...
3
votes
1answer
314 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 ...
2
votes
1answer
68 views

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 ...
9
votes
1answer
1k views

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?
3
votes
3answers
128 views

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 ?
2
votes
0answers
53 views

First ionization energy of hydrogen molecule

If we have the dissociation's energies of hydrogen molecule $\ce{H_{2}}$($D_{0}$) and the corresponding molecule ion $\ce{H_{2}^{+}}$ ($D_{1}$) together with the first energy of ionization of hydrogen ...
7
votes
2answers
103 views

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 ...
10
votes
1answer
480 views

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 ...
4
votes
1answer
113 views

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 ...
6
votes
2answers
148 views

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 ...