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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1answer
95 views

Lother Mayer curve

While studying about atomic trends, I encountered the Lothar Meyer curve: Similar graph found on internet If the covalent radius decreases across a period, why is the graph of atomic volume ...
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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.
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The ambiguity regarding aufbau principle

According to a Blog https://ericscerri.blogspot.com/2012/06/trouble-with-using-aufbau-to-find.html written by Dr.Eric Scerri, On moving from the $\ce{Sc^3+}$ ion to that of $\ce{Sc^2+}$ it is plain ...
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1answer
263 views

How to derive the number of spectral lines?

Recently, I found that when electrons in an atomic sample de-excite from a higher energy level ($n_2$) to a lower energy level ($n_1$), the number of spectral lines observed in the spectrum is $$\frac{...
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2answers
193 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?
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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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1answer
81 views

How is the molar weight of C-12 equal to 12 gram ? Why is “g” not considered while calculating molar weight? [closed]

So, I was just pretty confused about how we simply multiply the "mass" of total nucleons in Carbon by the Avogadro Constant, to get the molar "weight" as 12 grams, shouldn't it be ...
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1answer
54 views

How is most probable radius in quantum mechanical model equal to Bohr's radius in hydrogen atom

Most probable radius in 1s orbital for hydrogen electron is $\pu{0.529E-10 m}$ which is Bohr radius. But energy of electron in hydrogen atom is proportional to mean radial distance in atom. In this ...
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2answers
7k views

Transition from ground state to excited state

I don't understand how to correctly find the term symbol of an excited state. I know that the first two permitted transitions for the Ne atom are 16.8eV and 19.8eV and I want to find the electronic ...
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1answer
62 views

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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2answers
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What would happen if the alpha particles directly hit the electrons in the gold foil in Rutherford's experiment? [closed]

What would happen if the alpha particles directly hit the electrons in the gold foil in Rutherford's experiment? Would it get ionized or is there no probability of such a thing happening ?
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Are orbitals always filled in from closest to nucleus to farthest away?

In which orbital, 4f or 6s, would an electron have a greater likelihood of being near the nucleus. I figured that the 6s would be closest, since it is filled in first when using the Aufbau principle. ...
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2answers
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Periodic Trends of Zeff and Electronegativity

The effective nuclear charge $Z_\mathrm{eff}$ increases from left to right and from top to bottom. Can you explain why it increases from top to bottom? Also can we explain the periodic trend of ...
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1answer
177 views

Find the amount of atoms for a given mass

The atomic mass of two elements A and B is 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B? I have tried to solve by assuming that x g of A has y atoms ...
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Why are electrons filled in fourth shell before the third shell is filled?

I am a beginner and am learning about atomic structure and I am getting confusions regarding the aufbau principle. It is said that the electrons will be filled first in lowest available energy level. ...
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1answer
456 views

Are the rules proposed by Slater for the calculation of effective Z right?

Today I studied Slater's rules for calculating the effective nuclear charge. 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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1answer
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Why should the redox reaction happen between the copper ions and iron atoms?

I know that when $\ce{Cu^{2+}}$ ions react to $\ce{Fe}$ atoms, it becomes $\ce{Cu}$ + $\ce{Fe^{2+}}$. My question is, why? Copper atoms normally have 29 electrons. This means that in the K-shell there ...
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If an atom had 200 protons, how much neutrons would it need to have to be most likely stable and why?

I know there is a specific proton/neutron ratio but i'm unaware if it applies to atoms with 86 protons and beyond.
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2answers
6k 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 ...
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0answers
42 views

Why is atomic mass unit/unified atomic mass defined against Carbon 12?

I have searched the web all over this question and I have not really found an answer to my satisfaction. From my understanding of the topic so far, I understand that reason why concept of unified ...
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2answers
9k views

If the reactivity of group 1 elements increases down the group, why is this not the case for halogens? [closed]

I was wondering, as you go down a group, the atoms get bigger... This means that the electrons in the outer shell are further away from the nucleus, and so the attraction decreases and it is easier ...
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1answer
23 views

When is the n+l rule followed when working with energy of different orbitals?

While going through my book, I came across a problem which gave some options about the order of energy of 3s, 3p and 3d orbitals of hydrogen atom. The correct answer was given as: 3s, 3p and 3d ...
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1answer
11k views

How to find the number of hydrogen atoms in 0.5 mol of hydrogen gas?

How do I calculate the number of hydrogen atoms in $\pu{0.5 mol}$ of hydrogen gas? I presume the answer would probably somehow use the equation $$n = \frac{m}{M},$$ where $n$ is the amount of ...
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0answers
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D block elements electronic configuration

We have found the electronic configuration of d block elements.As we move from left to right in the periodic table the energy of the 3d subshell is decreased and it becomes smaller than the energy of ...
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1answer
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Atoms vs molecule when talking about the avogadro's number? [duplicate]

By far, my understanding is that a molecule is made up of atoms bonded together. For example, a molecule of water ($\ce{H2O}$) has 2 hydrogen atoms and one oxygen atom. However, when it comes to ...
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3answers
50k views

How to calculate the number of atoms of each element in a urea?

I have a stoichiometry question which I answered incorrectly and I am not sure where I went wrong. The question is as follows: Urea, $\ce{(NH2)2CO}$, is used for fertilizer and many other things. ...
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2answers
87 views

Why electrons do not distribute evenly among the atoms in a molecule? [closed]

I was wondering why the state where electrons are evenly (or the closest to being evenly) distributed among the atoms in a molecule is not the lowest energy state? For example, in a water molecule it ...
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1answer
186 views

Why is the ionic radius of hydride so large?

The order of ionic radii for halides and hydride is apparently as follows: $$\ce{F-} < \ce{Cl-} < \ce{Br-} < \ce{H-} < \ce{I-}$$ Why is the hydride ion so large, even larger than bromide ...
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1answer
47 views

Rutherford's Alpha Ray Scattering Experiment & Plum-Pudding Model

My teacher said, "Rutherford thought that all the Alpha particles would directly go through the gold foil without any collision if the plum pudding model was right. Because, as said in plum ...
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1answer
99 views

Schrodinger's Equation and Wave Function

So I understand that there exists the shrodinger's equation, which on solving,gives the wave function of an electron. The wave function as I understand, gives all possible information about an ...
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1answer
45 views

Could observer effect cause electrons in one orbital to be found in another?

The observer effect states [1] that when unobserved, absolutely small particles like electrons can simultaneously be in two different states at the same time. If we look at an atom of any element, ...
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1answer
119 views

Is this bond Ionic or Covalent, and why? AlBr [closed]

We know a compound could form between NaCl because they are +1 and -1 ions which make them both into a complete valence set. Could a compound form between Al and Br, for example, and what type of bond ...
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3answers
837 views

Why do electrons jump back after absorbing energy and moving to a higher energy level?

Electrons in a shell absorb energy and move to higher energy levels, but they release their energy and jump back to the shell they originally were in. Why do they jump back? Why can they not keep ...
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0answers
38 views

Does the electron in a neutral hydrogen atom ever exist in the p, d or f sublevels?

I learned that the electron in a neutral hydrogen atom can be excited to higher levels. But there are different sublevels in the levels. For example s, p, d and f. Does the electron only jump from s ...
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1answer
91 views

What does orbital mean, exactly? [duplicate]

My teacher told me that orbital is the probability distribution data of the electron around nucleus which is amplitude data in a way. An example of how my teacher actually told what it means involves ...
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1answer
119 views

Why is the atomic mass unit less than the mass of both a neutron and a proton? [duplicate]

The atomic mass unit is $1.6605 \times 10^{-27}$ kg. This is less than the mean of the masses of 6 protons and 6 neutrons. How do we account for the lower mass ? My understanding is that some of the ...
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3answers
376 views

Does electron mass decrease when it changes its orbit?

I have studied this in my chapter atomic structure that when an electron changes its orbit from lower energy to higher energy state , it does not state in my book that it moves there but that it ...
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2answers
75 views

How is this possible in mole concept? [closed]

L = $6.022*10^{23}$ If I have one atom of oxygen , it has exactly L value. Now 2 atoms of a oxygen have 2L value.(Note that I mean 2O and not $O_2$here) Well , if we take a molecule made up of 2atoms ...
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1answer
87 views

What does Pauli’s exclusion principle mean in atomic or fundamental way? [closed]

It means is that no electron can have same n , l and $m_l$ but can have two different spin quantum number. I want to know why is this rule valid?Means there must be some other things happening also ...
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2answers
270 views

Atomic Orbitals

I read in a textbook that after an electron jumps to a higher energy level when supplied with high temperatures or current, they again fall back to their respective energy level by losing energy and ...
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1answer
233 views

Is this diagram correct for difference between 2N and N2

There is 1 $\ce{N2}$ molecule formed with 2 atoms of nitrogen. 2N is 2 separate nitrogen atoms which have not formed any bond.Reasons could be that they didn’t get enough energy to form bond so they ...
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1answer
74 views

Why do Rydberg atoms have electrons that can transition above the first ionization energy?

Why do Rydberg atoms have electrons that can transition above the first ionization energy? This can only happen in a multi-electron system but I don't see how the Rydberg formula would even work for n ...
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2answers
938 views

Spiralling of electrons into the nucleus

A drawback (and a major one) of Rutherford's model was that the electrons, being accelerated charged particles, would gradually spiral into the nucleus and collapse into it. My question is how did ...
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24 views

Why hydrogen gas tube produce hydrogen atomic spectrum

To measure the atomic hydrogen spectrum people often uses hydrogen gas tubes as light source. Since the gas in the tube is the molecule $H_2$ , why we obtain the spectrum of atomic hydrogen? My guess ...
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1answer
95 views

Why does matter have spaces between them? [closed]

If you mix sugar Crystal in a glass of water and mix it well, the level of water will not rise.The reason they say is that matter have spaces between them.If matter have spaces between them , How ...
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5answers
435 views

Why don't electrons simply stick to the nucleus on account of being *oppositely* charged, instead of moving around it? [closed]

Why don't electrons stick to the nucleus on account of being oppositely charged charged (the nucleus being positively charged)? But contrary to my intuition, electrons seem to follow a whole bunch of ...
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1answer
82 views

“Isotopes” in a molecule?

I just learned that atoms of the same element can have different mass because of they are isotopes. If there are two isotopes in which each reacts to form the same thing. Would the mass differ in each ...
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3answers
1k views

Is the boundary of an atom well defined?

That question might seem weird, but that's what I have been imagining lately; going through Bohr's theory on the hydrogen atom. He clearly defines the radius of an orbit with an exact mathematical ...
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1answer
3k 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 ...
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1answer
16k views

Why is the relative atomic mass of carbon not exactly 12?

Relative atomic masses of atoms of all chemical elements are numbers without units, being the value of proportion compared to $\frac{1}{12}^\text{th}$ the mass of the carbon atom. But the relative ...

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