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 true depiction of the periodic table?

Normally with the periodic table the lanthanide series is separated out because it's long and would make the table wide. I looked for an expanded version and found this: I found it kind of strange ...
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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 ...
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Why do atoms have electron Affinity? [duplicate]

Atoms are stable so how can they pull electrons i.e how do they have any electron affinity at all?
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Is neutron a compressed form of hydrogen atom?

As I know: $E_\mathrm{p} = \pu{938.272 MeV}, \quad E_\mathrm{e} = \pu{0.511 MeV}, \quad E_\mathrm{n} = \pu{939.565 MeV}$ $E_\mathrm{n} − (E_\mathrm{p} + E_\mathrm{e}) = \pu{0.782 MeV}$ $M_\...
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Rutherford's alpha particle scattering experiment for sheets made of different metals [closed]

The correct order of increasing number of alpha particles passing undeflected through the foils of Au, Ag, Cu and Al of 1000 atoms thickness each in an alpha scattering experiment of Rutherford would ...
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As an atom get's bigger (on increasing atomic no.) , electrons have to move faster and faster around the nucleus, Why?

Does speed even make sense at such small scales ? Heisenbergs Uncertainty principle ?
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Trying to understand the contradiction in the data of Proust/Dalton/Berzelius vs Gay-Lussac

I am trying to understand some of the historical context behind the discovery of atoms (pre-Avogadro). In particular, I am getting stuck in reading the following documents: http://physics.unl.edu/~...
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Are ions actually charged particles?

For instance, if an atom loses an electron and becomes a cation, such as sodium, how does that make the sodium atom positively charged? The sodium's atomic radii decreases due to less electron-...
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1answer
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Finding molecules that you randomly create using a modeling kit

I recently bought https://snatoms.com/ (which is just a real-life modeling kit for atoms/molecules) and was just keen on learning about chemistry in general. I often randomly join atoms to make up ...
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Quantum Mechanical Model of An Atom, Shells, Subshells [duplicate]

I've just been introduced to the quantum Mechanical Model of an Atom, so please bear with me on this one. Are Subshells and shell physical things, like do they really exist, or is it a concept only to ...
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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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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
230 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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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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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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1answer
128 views

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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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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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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1answer
33 views

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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2answers
186 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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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 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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Is it possible to speed up radioactive decay?

I’m aware that elements like $\ce{^14C}$ have a known half-life, which means that over a span of roughly $5730$ years, half of the $\ce{^14C}$ atoms decay into $\ce{^14N}$. Are there any substances ...
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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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4answers
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In helium-2, would each electron experience a single positive charge from the nucleus?

If we have an atom of hydrogen-1, we know that there exists one proton with one electron and in helium-2 two protons with two electrons. My question is that do protons get shared equally with ...
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3answers
871 views

Formation of Hydrogen - from a proton and an electron [closed]

If I place a proton and an electron close to each other, can they form an atom of hydrogen? Why or why not? Please explain the scenarios where this is not likely/unlikely. Personally I doubt it, ...
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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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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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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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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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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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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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718 views

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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What is the physical state of a single atom?

Can a single atom on its own be either a solid, liquid, or a gas? Or is it none of them?
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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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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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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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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
655 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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Schrödinger equation for multi-electron atoms

Does the Schrödinger equation alter its form when we apply it for an atom having a configuration other than hydrogen-like? I think it should happen because of difference in nuclear attraction and ...
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1answer
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Ionisation energy [closed]

Explain why the 1st ionization energy of boron is less than that of beryllium, whereas the 2nd ionization energy of boron is greater than that of beryllium.
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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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Effects of Ionizing a Radioactive Isotope

If you took your favorite radioactive isotope and ionized it using a strong electric field (or any other ionization method), thereby stripping it of an electron, what would happen when it decayed? For ...
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916 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 "...
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1answer
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How right is defining elements with the number of protons? [closed]

Atomic number is the number of protons a certain atom has. It's the defining attribute of a certain element. But, How right is that? From the viewpoint of chemistry, the definition is right. Because, ...

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