Questions tagged [atoms]

Smallest particle still characterizing a chemical element. It consists of a small nucleus charged positively, carrying almost all of the atom's mass, with electrons surrounding it. This tag should be applied to questions that specifically concern atoms or their properties. For the charged particles, please use [ions] instead. If your question is specifically about [protons], [neutrons], or [electrons], use those tags instead.

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52
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5answers
10k views

The last element's atomic number

I was just thinking what can be the last atomic number that can exist within the range of permissible radioactivity limit and considering all other factors in quantum physics and chemical factors.
22
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1answer
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Why are atoms with eight electrons in the outer shell extremely stable?

Atoms that have eight electrons in their outer shell are extremely stable. It can't be because both the $s$ and the $p$ orbitals are full, because then an atom with 13 or 18 valence electrons would be ...
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3answers
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How to get the valencies of elements?

How to find the valencies of elements by using its distribution of electrons? Please explain the method in simple words. Do you have to study the valencies or is there a simple way of remembering? PS:...
5
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1answer
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Units of mass on the atomic scale

what are the systems of recording atomic masses and their units? I know that the nucleon number is the number of protons and neutrons I also know that the mass number on the periodic table is the ...
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1answer
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While filling electrons, we follow Aufbau principle, but not while removing them. Why is this so?

I recently came across a question Why is the vanadium(3+) ion paramagnetic?, where the asker is wondering how $\ce{V^{3+}}$ is paramagnetic (he used Aufbau in reverse to remove the electrons), while ...
8
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1answer
867 views

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 ...
5
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3answers
1k 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 ...
11
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1answer
16k 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?
7
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2answers
780 views

Rutherford's Alpha Ray Scattering Experiment

I understood the result of this experiment that the nucleus is nearly empty and things like that. But what I have on mind is that when an alpha particle goes nearer to the thin gold foil why couldn'...
26
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2answers
32k views

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 it....
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4answers
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What is the difference between physical and chemical bonds?

If you characterize the chemical bonds to two categories physical and chemical bonds, how do you do it? Aren't all bonds chemical and physical? From the freedictionary.com, chemical bond: Any of ...
14
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1answer
4k views

Why are the masses of atoms less than the sum of their subatomic particles?

The mass of carbon-12 is $\pu{12 u}$ by definition. However, one carbon-12 atom comprises 6 neutrons (each weighing $\pu{1.0087 u}$), 6 protons (each weighing $\pu{1.0072 u}$), and 6 electrons (each ...
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What actually is the Wavefunction?

I am aware that the square of the Wavefunction gives the probability density of finding an electron at a particular point in space. I have also heard that it's a complex number but since it's a ...
8
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1answer
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Is it possible to have a diatomic molecule of sodium in gaseous state?

Already I know that hydrogen, all the halogens, nitrogen and oxygen forms diatomic molecules. But I am confused about $\ce{Na}$? So I would like to know about that.
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1answer
456 views

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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2answers
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Mass number, (relative) atomic mass, average mass

What is the difference between mass number, atomic mass and average atomic mass? I know the mass number is the amount of protons + the amount of neutrons. The average mass is the weighed average of ...
37
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5answers
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How do I visualize an atom?

I have searched and searched, oh how I have searched. I am looking for a 3-dimensional visualization of a whole atom, one that that includes all the orbital geometry. A proper "layered" view of the ...
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3answers
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Why are atom spherical in shape ?

I am learning about structure of atom, in which i saw right from J.J. Thomsom atomic model to modern nuclear atomic model all are spherical in shape. I have seen how different discoveries help to ...
35
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4answers
29k views

Why do atoms generally become smaller as one moves left to right across a period?

It seems to me that the addition of electrons and protons as you move across a period would cause an atom to become larger. However, I'm told it gets smaller. Why is this?
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Why does free chlorine in the stratosphere lose its ozone-depleting potential after about 100,000 reactions?

Free chlorine ($\ce{Cl}$) in the stratosphere can deplete ozone ($\ce{O3}$) as follows: $$\ce{Cl + O3 -> ClO + O2}$$ The chlorine atoms can then react with oxygen and return to the beginning of ...
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1answer
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Whats the difference between ionization energy and orbital energy?

If you look at the trend in orbital energies as you go across a period the pattern is clear (orbital energy decreases with increasing effective nuclear charge) and, to my knowledge, it has no ...
14
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1answer
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Which elements can be diatomic?

Which elements can be diatomic and why? Motivation Hydrogen, Nitrogen, Oxygen and the Halogens tend to be thermodynamically stable as a diatomic molecule at room temperature, and are usually ...
8
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1answer
821 views

Effects of Changing Avogadro's Constant

The Avogadro project suggests that we redefine the Avogadro constant to be equal to our best known estimate, $N_\mathrm{A} = 6.02214179 \times 10^{23}$, and redefine the kilogram based on the Avogadro ...
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1answer
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Do electrons in an atom revolve around the the nucleus clockwise or counterclockwise? [closed]

Do electrons in an atom revolve around the the nucleus clockwise or counterclockwise? Is there any rule to determine?
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5answers
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What is SPDF configuration?

Recently in my chemistry classes, the teacher spoke about SPDF configuration and then said that we'll be taught about it in higher classes. But I'm sorta curious to know that what is SPDF ...
9
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1answer
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How can two orbitals constructively and destructively interfere simultaneously?

The molecular orbital theory dictates that when two atomic orbitals form molecular orbitals, then two molecular orbitals must form (i.e number of atomic orbitals = number of molecular orbitals). For ...
6
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2answers
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How can two electrons lie together in an orbital?

Two electron of opposite spin can lie in a single orbital.. But what about the electron-electron repulsion. Okay! I got that the nuclear charge rather the large Z-effective overcome this repulsion by ...
16
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2answers
8k views

Are atoms really round?

I'm not sure if this is a silly question, but I was sitting here with a cup full of cheezey poof balls thinking, "My goodness, it's like an amazing cheesey delicious liquid - huge water molecules!" ...
18
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6answers
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What is the difference between an element and an atom?

First, I would like to quote sentences from a book introducing elements and atoms: An element is a fundamental (pure) form of matter that cannot be broken down to a simpler form. Elements are made up ...
11
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4answers
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Why do people still use the mole (unit) in chemistry?

I know that the mole is widely used in chemistry instead of units of mass or volume as a convenient way to express amounts of reactants or of products of chemical reactions. I'm wondering why people ...
13
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2answers
973 views

NMR chemical shift range of different elements

A typical $\ce{^1H}$ NMR runs from approximately 0 to 10 ppm, give or take a bit. $\ce{^13C}$ NMR runs from 0 to 200. And $\ce{^59Co}$ NMR runs from -5000 to 15000 ppm! There seems to be some ...
9
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1answer
7k views

Anomalous Electronic Configuration of Thorium

The electronic configuration of thorium ($Z=90$) is $5\mathrm f^0 6\mathrm d^2 7\mathrm s^2$. But, according to the aufbau principle, the electrons should first enter the $\mathrm f$ subshell and not ...
5
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1answer
7k views

Sulfur trioxide - vacant d-orbitals

Sulfur trioxide violates the octet rule. Upon drawing the Lewis dot structure for sulfur trioxide, we see that the central sulfur atom is bonded to three other oxygen atoms by double covalent bonds. ...
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2answers
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Quantum mechanical model of atom and the quantum numbers

I studied Bohr's model of atom and then the drawbacks of it and then quantum mechanical model of atom. Now quantum model is according to uncertainty principal and dual nature of matter and it says we ...
3
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1answer
1k 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 ...
31
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1answer
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Why are there two Hydrogen atoms on some periodic tables?

Most periodic tables only feature one Hydrogen atom, on the top of the first group. But some, like the one I was given, also show Hydrogen in the 7th group, to left of Helium. Why are there two ...
6
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2answers
970 views

Do hybrid orbitals exist in unbonded molecules? What would they look like?

For example, the ground state of a neutral carbon atom could be notated as: $$ [\ce{He}] \underset{\ce{2s}}{[\uparrow \downarrow]} \underset{\ce{2p}}{[\uparrow \vert \uparrow \vert \; \;]} $$ I ...
6
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1answer
1k 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?
3
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2answers
92 views

Atomic weight = expected weight?

The atomic weight of an element, is it accurate to say that another way to think of it is the expected value of that element's weight if we were to sample one at random from the environment? Are man-...
5
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3answers
2k views

Conversion atom to another

One child has claimed to have find a solution to all physical problems. On asking for details, he said that all periodic elements has common components, i.e. electrons, protons, neutrons. The child ...
3
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3answers
5k views

In nuclear chemistry, how does a neutron split to form a proton and an electron?

I'm studying radioisotopes at the moment and balancing nuclear reactions isn't making sense in that more matter is coming out of the equation in negative β⁻ decay equations: $$\ce{_6^{14}C -> _7^{...
3
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2answers
188 views

What is 'space'? [closed]

What is in the space between atoms? I understand that molecules are constantly being formed from collisions and such, but what I do not understand, is, on a tiny level, within the level of the atom, ...
3
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1answer
749 views

Electron pairing and repulsion [duplicate]

If two electrons that get paired occupy the same orbital, then wouldn't there be a heavy amount of repulsion between the two? As is, since electrostatic force ${\displaystyle \propto }$ $\ce{ 1/ (...
1
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1answer
595 views

How are the molar mass and molecular mass of any compound numerically the same?

This observation is really annoying me, and the internet isn't providing me with any solid answers. Either their definitions of molar mass completely differ, or they don't stick to their own ...
0
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1answer
131 views

Atomic properties [closed]

This may be a very broad question. I always asked myself how scientists manage to find out the exact molecular structures of for instance water or carbohydrates. How do they know? How do they know the ...
20
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6answers
19k views

Why do atoms need 8 electrons to stabilize? [duplicate]

As the title says. I have surfed all of the net but could never find the answer to this question. Why do atoms need 8 electrons to stabilize? I mean why not 7 or 5 or 10 electrons? Why specifically 8? ...
17
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4answers
2k views

Why is the electron-nucleus attraction modelled with only electrostatic interactions?

While reading about the structure of an atom, I've encountered (even in some renowned books) the statement that electrons and nuclei are attracted due to electrostatic, or Coulombic, attractions. ...
11
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1answer
708 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 ...
4
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3answers
10k views

Is a single carbon atom stable?

It is well known that single atom of oxygen is not stable, and it forms $\ce{O2}$ molecule. But elements like carbon form a network of repeated bonds. As answered in another question, last atoms in ...
4
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2answers
6k 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 ...