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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What is the difference between ''1 C atom and 1 mole of C atoms?'' [closed]

Does 1 C atom mean 1 single C atom out of Avogadro's number of C atoms = 1 single C atom out of 6.023 X 10^23 numbers of C atoms? Does 1 mole of C atoms mean Avogadro's number of C atoms = 6.023 X 10^...
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A mole of atoms is the number of atoms whose total weight equals the atomic weight?

My textbook says, a mole of atoms is the number of atoms whose total weight = the atomic weight. There's something in the definition that's confusing me. Now what is confusing me is: Atomic weight =...
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74 views

What makes bond break apart from heat? [closed]

What makes bonds break apart from heat? I am wondering if anyone could explain the reasons why new bonds are formed in the absence of energy. I have found that they form in order to lower the overall ...
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How did the atomic number and atomic mass of elements discovered? [closed]

Elements are small for our naked eyes.so,how did the discovery of its atomic number and mass number took place?
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Why do objects gain electrons? [duplicate]

I have read that objects gain electrons to become negatively charged and also that they lose electrons to become positively charged. I have also read that same charges repel each other and non-same ...
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1answer
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Can there exist any element which has an 8th principle shell?

I am a high school student . While studying the atomic structure a question raised in my mind. We know that an atom can have the highest limit of 7 bohr energy shells or principle energy shells ; K,L,...
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233 views

Atomic structure [closed]

We've got a homework and I know this question may seem so primitive, but I have already read whole textbook and I've been looking also on the Internet, but I still cannot find the right answer. I'd be ...
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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 ...
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1answer
163 views

How are ions formed? [closed]

I know that $\ce{H2O}$ is neutral. So how does adding one more hydrogen atom to it make it positive ion ($\ce{H3O+}$)?
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555 views

Why is the ionization enthalpy of francium greater than that of cesium?

Why is the ionization enthalpy of francium greater than that of cesium, even though it has a larger size? I found no Google result regarding this.
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Why were elements discovered "out of order" after 1950?

I'm referring to the fact that there is one element that corresponds to one proton in an atom, a second that corresponds to two protons, up to, I believe, an element with 115 protons. These elements ...
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How isotopes atomic mass was defined?

So we say that 1 Amu (u) = 1/12 of the mass of a Carbon 12 atom. Im not sure about this, but I believe that first we measured the mass of 1 carbon 12 atom (This includes the mass defects that occur ...
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Carbon tetraradical

I was just reading through Reactions: The private life of atoms by Peter Atkins and I noticed that in Chapter 3, the chapter on the combustion reaction, the author writes: As we watch we see $\ce {...
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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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Is it possible to compress an atom to infinite density? [closed]

I know, by nature, normally atoms are stable. But I wonder, if it is possible to compress an atom, say the Hydrogen atom, to infinite density by applying external force? After all, electrons and ...
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What is the electron configuration for Og with a charge of 2-?

I was writing a cool program that determines the electron configuration of elements for me, and I wondered what would happen if you went over 118 — the "limit" of my program. So, what is the ...
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Emission spectra [closed]

I am a highschool student and I am really confused about the following: We studied that electrons cannot be between main energy levels therefore in an emission spectrum of an element lets say hydrogen ...
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How do I find the diameter of an aluminum atom from its density and atomic mass? [closed]

I am supposed to find the diameter of an aluminum atom using data given by my teacher. Here is the data: \begin{array}{cc} \text{Density of Aluminum}& \pu{2.70 g/cm3}\\ \text{Atomic Mass of ...
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188 views

Atomic mass number and mass number in atomic symbol

In chemistry classes or even many different branches of chemistry textbooks, I am told that the atomic symbol $$\Large ^A_Z\ce{X}$$ includes the following notations: $A$ – "atomic mass" or "mass ...
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Why do electrons need to be paired?

I’d read that it takes energy to place electrons in pairs, just less than it would take to place two electrons in different subshells. I get that. What I don’t get is, then, why would electrons want ...
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How many atoms are represented in this equation?

$\ce{Pb(NO3)2 + 2KI -> PbI2 + 2KNO3}$ The answer says 26, but shouldn't it be 13? Because actually, the number of atoms involved in the reaction are 13, and once the reaction is completed, again, ...
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What is the reason behind choosing the specific elements used for the synthesis of heavier elements?

The following has been derived from the wiki page "Extended periodic table" and is one of the many examples d or f block elements being used in synthesizing new heavier elements (or at least this is ...
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1answer
137 views

What does "atoms make no compromises" mean?

I was watching The Ring of Truth - 5 Atoms and in the last part of the movie (the link starts at this part), Dr. Morrison said "When it comes to energy, atoms make no compromises. It is all or ...
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Comparision of the Ionisation Energy Change of the alkali metals and noble gases?

Currently I compare the ionisation energys of the alkali metals: Li: $\pu{0.52 eV}$ Na: $\pu{0.50 eV}$ K: $\pu{0.42 eV}$ Where only a slight drop (appr. remain constant) occurs. This ionisation ...
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An elementary question worth asking [closed]

We all know that an atom starts moving faster when it's heated.But actually atom is not some new thing itself in the sense that it is just a bunch of electrons and protons. So, I think that same ...
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1answer
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Why doesn't velocity enter into Heisenberg's Uncertainty Principle?

So I came across Heisenberg's uncertainty principle in my 11th grade book, and I'm not convinced. It says $\Delta x \Delta p \gt \frac{h}{4\pi}$. Okay, but how does velocity even matter to determine ...
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1answer
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Numerical value of mole [closed]

Why is the numerical value of a mole of atoms equal to the atomic weight? For example, hydrogen has an atomic weight of 1.008, so 1 mole of hydrogen atoms has a molar mass of 1.008 g/mol. Why?
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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 )}^3\frac{(n-\ell-...
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1answer
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Orbital diagram in which the Aufbau principle is violated [closed]

The orbital diagram in which the Aufbau principle is violated is: The answer given for this question is 3, but according to me if asked for Hund's rule violation then it would be 1, as electrons ...
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1answer
400 views

Are electrons in a helium atom diametrically opposite? [closed]

The helium atom is represented with electron opposite on same orbital: not fully opposite on same orbital and even on two normal orbitals: But in this case wouldn't the electron crash? Can you ...
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1answer
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Calculating nearest neighbor distances

For cubic materials, there are equations in which to calculate nearest neighbor (NN), second nearest neighbor, etc. Can this be done with tetragonal crystal structures? I want to calculate NN, 2NN, ...
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2answers
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Does the distance between an electron and the nucleus change for excitation and relaxation?

According to the Bohr model, when an electron moves from a ground state to the excited state, it will absorb energy, but what about the distance between electrons and nucleus, will it be changed? Why ?...
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How can we measure the atomic radius of an atom?

The definition of atomic radius is half the average internuclear distance of an atom. But many times I've been told that it is not possible to handle a single atom. Thus how can we measure the ...
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Inter electronic repulsion in s and d orbitals

This was written in a lecture slide: Two electrons present in the same d-orbital repel each other more strongly than do two electrons in the same s-orbital. Why is there a difference in the amount ...
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Is Effective Nuclear Charge the same as Core Electrons?

I'm wondering, what is the difference between the two? Using the equation for Eff: $\ce{Zeff = Z - S}$ Z being the number of protons in the nucleus and S being inner-shell electrons. For example: ...
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1answer
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Calculating the ionization energy for hydrogen

What energy would be needed to remove the electron from the $n = 4$ level of the hydrogen atom? $\pu{−3.49 * 10^{−17} J}$ $\pu{−1.36 * 10^{−19} J}$ $\pu{+2.18 * 10^{−18} J}$ $\pu{+1.36 * ...
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1answer
76 views

What reaction is expectable from the atomized reactants?

Let we have a reaction that starts from some reactants to produce some products. When the activation energy is provided to the reactants they will be atomized and produce a gas of individual atoms. ...
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Calculate the number of atoms of oxygen present in 1.3 mol of sulfuric acid

Calculate the number of atoms of oxygen present in $\pu{1.3 mol}$ of $\ce{H_2SO_4}$ 1 mol has $6.02\times 10^{23}$ atoms So $\pu{1.3 mol}$ must have $1.3 \times 6.02 \times 10^{23} = 7.826 \times 10^...
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4answers
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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. ...
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1answer
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What atom is always paramagnetic and why?

Regardless of its electron configuration, it must always be paramagnetic when it's a single, neutrally charged atom: (A) Carbon (B) Nitrogen (C) Oxygen (D) Neon (E) Argon At first, I eliminated D ...
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1answer
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How do we know the number of s and p orbitals in a shell?

How do we know how many s & p orbitals will be in a shell? There is one 2s orbital and three 2p orbitals in shell #2. There is one 3s orbital, three 3p orbitals and five 3d orbitals in shell #3....
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1answer
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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?
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discover of the neutron, what happen to 2+ charge

James Chadwik found the neutron by shoot α rays to a Beralium foil. α rays are equal to the He²⁺ and he saw that particles without a charge is out from that. He understood the neutrons are those ...
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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 ...
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2answers
382 views

Energy of the n-th level for an atom

Going through the Bohr's model and his assumptions, I came across with this formula to find the energy of the n-th level of any atom: $$E = - \frac{Z k_e e^2}{2r_n} = -\frac{Z^2(k_e e^2)^2m_e}{2\...
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2answers
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How many electrons with l = 1 does Si in its ground state have?

I was solving practice problems for electron configuration and periodic table, and I got stuck through a question: An atom of silicon in its ground state has how many electrons with quantum number $...
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Electrons in orbitals with nodes [duplicate]

Node is a region in atomic orbital where there is no possibility of finding electrons. That is no electron can be found there (region of $\psi^2 = 0$) Take example of say $\mathrm{2s}$ orbital: as ...
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1answer
680 views

Energy levels in non-hydrogen-like atoms

The energy $E_n$ for a hydrogen like atom is given as $$E_n = -hcR_\ce{H}\frac{Z^2}{n^2}$$ However, aside from on wikipedia where there is $$E_n = -hcR\frac{Z_\text{eff}^2}{n^2},$$ I can't find ...
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Uncertainty of Atomic Mass [closed]

How should the uncertainty of the atomic masses of elements be quoted? E.g., Mg has an atomic mass of 24.31, what is that value's uncertainty?
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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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