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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Comparing average radius of subshells

I recently came across a question comparing the average radius of subshells. A search on the internet gave the following result for single electron atoms: $$\langle r\rangle_{n,\,l}=\frac{a_0 n^2 \...
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Why do Atoms Come Close to form Molecules? [closed]

I am confused in the topic related to formation Of molecules from Atoms,Why do the Two atoms come close to each other,For example Every Neutral atom has equal number of Electrons and protons ,hence ...
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Identity of metal [closed]

1.15g of metallic element reacts with 300cm^3 of oxygen at 298K and 1atm pressure, to form an oxide which contains O²- ions. What could be the identity of the metal? The answer is sodium. But how and ...
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How many atoms are there in single element? [closed]

Elements are chemical substances made up of the same types of atoms (atoms with the same proton number), whereas molecules are chemical compounds made up of atoms from two or more different elements. ...
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1answer
31 views

Why does increasing subshell cause ionization energy to decrease?

I know that increasing subshell decreases ionization energy; for example, going from Beryllium to Boron. I do not understand why this is. The answer my textbook (Chemistry 2e on OpenStax) gives is ...
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respective posistion of d and p orbitals in a multielectronic species

we write the electronic configuration of atoms as [noble gas core]4s2 3d10.that is that due to energy considerations(aufbau principle) in multielectronic species. what i want to know is whether the 4s ...
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109 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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1answer
84 views

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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270 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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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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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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56 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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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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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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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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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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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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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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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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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
48 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
110 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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131 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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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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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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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
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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
157 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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396 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
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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
88 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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280 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
75 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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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
100 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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1answer
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"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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1answer
76 views

Hydrogen and Hydrogen ion

Is it correct that a hydrogen atom only has 1 electron and 1 proton since the atomic mass is 1? Also, is the hydrogen ion composed of a single proton and no electrons? In an ionization process we know ...
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Reason for needing multiple radii for the same atom [duplicate]

Why do we need different types of atomic radii? Why can't there be just one radii for an atom?
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1answer
172 views

In metallic bonding, what causes a metal to lose its outer electrons and become an ion? [duplicate]

In metallic bonding, what causes a metal to lose its outer electrons and become an ion? I am trying to understand metallic bonding, atoms and ions.
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1answer
55 views

Why does covalent bonding not break down if observer effect can be applied to atomic electrons? [closed]

The observer effect in quantum mechanics states that when unobserved, quantum particles such as electrons can simultaneously occupy two different states. In an atom of any element, where there are ...
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758 views

Does the 4s orbital really have a higher energy level compared to 3d? [duplicate]

For writing the electronic configuration of the $\ce{Fe^2+}$ ion, you need to remove two electrons (as it is an ion) which are from the highest energy level. Apparently, this would be $\mathrm{4s}$ ...
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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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249 views

Rules to follow while writing a chemical formula for polyatomic ions

In Science, textbook for class IX, chapter $3$ [1,p.38], it states: The rules that you have to follow while writing a chemical formula are as follows: in compounds formed with polyatomic ions, the ...
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Illustrating moles with sand grains, Are there more moles of SiO2 in a grain than moles of sand on the earth

I have been trying to understand the scale of atoms, thinking about sand grains as an example. With approximately $7.5\times10^{18}$ grains of sand on the earth that is $1.25\times10^{-5}$ moles of ...
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498 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, ...
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214 views

Confusion with definitions of mass [duplicate]

What is the difference between: atomic mass relative atomic weight relative isotopic weight standard atomic weight atomic weight relative atomic mass I am told by Wikipedia that: relative atomic ...
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2answers
875 views

What is the dimension of Avogadro's constant?

What is the dimension of Avogadro's constant ($N_\mathrm{A}$). On Wikipedia it says it is dimensionless, but in Nigel Wheatley's article (pdf) On the dimensionality of the Avogadro constant and the ...
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1answer
152 views

While calculating the effective nuclear charge, why don't we consider effect of outer electrons on inner ones? [duplicate]

When calculating the effective nuclear charge for an electron, why do we only consider the repulsive effect of the inner electrons on the outer electrons? The outer electrons also repel the inner ones ...
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266 views

What were the expectations of Rutherford's gold foil experiment? [closed]

At the time when Rutherford's gold foil experiment was performed, Thomson's plum pudding model was believed to be true (at least by Rutherford himself and his students). With this model in mind ...

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