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.
103
questions
56
votes
6
answers
12k
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.
- 1,254
10
votes
1
answer
2k
views
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 ...
- 726
22
votes
2
answers
7k
views
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 ...
- 1,373
27
votes
1
answer
2k
views
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 ...
12
votes
1
answer
19k
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?
- 443
8
votes
1
answer
1k
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 ...
- 9,736
1
vote
2
answers
6k
views
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 ...
- 253
16
votes
1
answer
6k
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 ...
- 263
8
votes
2
answers
886
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'...
- 321
30
votes
2
answers
41k
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....
- 411
19
votes
4
answers
33k
views
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 ...
- 1,011
17
votes
2
answers
3k
views
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 ...
- 284
13
votes
2
answers
2k
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 ...
- 71.1k
11
votes
5
answers
4k
views
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 ...
- 9,736
10
votes
1
answer
3k
views
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 ...
- 9,736
9
votes
1
answer
1k
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 ...
- 195
8
votes
2
answers
3k
views
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.
8
votes
1
answer
1k
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?
- 241
5
votes
3
answers
2k
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 ...
- 333
4
votes
1
answer
4k
views
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 ...
- 9,736
38
votes
5
answers
7k
views
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 ...
- 686
37
votes
3
answers
46k
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?
- 817
13
votes
1
answer
7k
views
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 ...
- 583
5
votes
1
answer
10k
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. ...
- 191
2
votes
3
answers
19k
views
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 ...
- 5,077
2
votes
1
answer
1k
views
How did early chemists measure mass of atoms?
Here a book says that Berzelius measured atomic masses using a simple lab and his measurements was so close to modern results. Can someone explain how a person living in 19th century was able to ...
- 121
-1
votes
1
answer
1k
views
why "amu" is used as a unit in relative atomic mass? [duplicate]
Unified atomic mass unit (amu) is defined as $1/12$ of the mass of a Carbon-12. I want to know is this amu equal to $\pu{1.99e-23 g}$ and why do we use amu which is $1/12$ the mass of carbon? Why use "...
- 995
35
votes
1
answer
12k
views
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 ...
- 1,105
21
votes
5
answers
292k
views
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 ...
- 979
20
votes
7
answers
33k
views
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 ...
- 217
16
votes
1
answer
712
views
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, ...
- 185
16
votes
2
answers
10k
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!"
...
- 271
11
votes
4
answers
22k
views
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 ...
- 245
9
votes
1
answer
11k
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 ...
- 91
8
votes
3
answers
3k
views
The definition of formal Charge
Ok, most people including me know that formal charge is just a book-keeping tool. I know how to calculate it, apply it to Lewis structures etc etc. But I am confused in its very basic definition which ...
user2619
6
votes
2
answers
393
views
Is atomic weight universal?
Are we advanced enough to calculate the abundance of an element throughout the universe or is our atomic weight only based on the occurrence of an element in our planet alone?
- 71
6
votes
2
answers
2k
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
votes
2
answers
2k
views
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 ...
6
votes
2
answers
4k
views
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 ...
- 749
6
votes
2
answers
2k
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?
- 195
6
votes
2
answers
8k
views
Energy of electrons in the same subshell
So I have this quote from wikia (it's similar to my lecture pdf file) but I don't fully understand the statement
Although it is commonly stated that all the electrons in a shell have the same ...
- 383
5
votes
3
answers
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 ...
- 161
5
votes
2
answers
4k
views
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 ...
- 10.5k
5
votes
3
answers
1k
views
Stability of Bohr Orbits
In class we had been taught that Rutherford's model was unsuccessful because it failed to show that the orbits are stable because the electrons would lose energy because of electromagnetic radiation.
...
4
votes
2
answers
14k
views
Z* effective charge and Ionization Energy
I'm trying to figure out the patterns for Ionization Energies. I am familiar with the periodic trend, however things become quite different when we hit the 1st I.E. For example, Na has an I.E(1) of ...
- 143
3
votes
1
answer
2k
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 ...
3
votes
1
answer
1k
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/ (...
- 1,339
3
votes
3
answers
6k
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^{...
- 33
3
votes
2
answers
282
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, ...
- 381
3
votes
2
answers
130
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-...
- 197