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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71 views

Understanding water models?

I generally work on fluid flow, so some basic concepts in chemistry are new to me. Work I'm doing requires use of molecular dynamics (MD) to do classical potential simulations of water–NaCl systems ...
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462 views

Lennard-Jones diagram - what is on the x-axis?

I have a Lennard-Jones diagram here where I can't figure out, what is on the x-axis. G. Ertl, Angew. Chem. Int. Ed. 2008, 47 We are looking at a diagram for a molecule $\mathrm A_2$ composed of two $...
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Is nucleus at the centre of the atom? If so why?

In postulates of Bohr's model of the atom, it is said that the nucleus is at the centre of the atom. In Rutherford’s α scattering experiment he said that out of 20,000 alpha particles only 1 ...
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2answers
449 views

How to understand the concept of moles? [duplicate]

I have trouble relating to the mole concept. For example in a question like the following: How many moles of $\ce{K}$ are in 1 mole of $\ce{KOH}$? How is it that in 1 mol of $\ce{KOH}$ there ...
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139 views

Molecular Assembly Program

I'm not totally sure which Stack Exchange community this would go in, but Chemistry seemed best. I've been thinking for a long time now, that it would be cool to have a program where you could design ...
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7k views

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
286 views

Why does ionization violate the stable or lowest energy rule in atoms?

Electrons that fill orbitals always do so in such a way that the resulting structure has the lowest energy state possible, though there are anomalies like chromium and so on. But ionization no ...
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1answer
693 views

Finding the number of orbitals on a central atom

In $\ce{BeCl2}$ the number of orbitals on central atom, i.e. on beryllium, are 2. In $\ce{BF3}$, the number of orbitals on central atom , i.e. on boron, are 3. Similarly in $\ce{NH3}$ there are 4, ...
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1answer
100 views

Why is the amu of chlorine-35 less than 35? [duplicate]

My book says that a proton weighs 1.0073u, a neutron weighs 1.0087u, and an electron weighs 0.00055u. Now, why is the mass of chlorine-35 equal to 34.969? Are there not 17 protons, 18 neutrons, and ...
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Identifying orbital given electron probability density plot

Being a high-school student, I only have a qualitative understanding of the wave mechanical model of atom. Below are my inferences regarding the plot shown in the above picture: The concerned ...
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2answers
361 views

Strong or weak force between protons and neutrons?

I had learned that what keeps the protons and neutrons bound is the strong force and the weak force has to do with radioactive decay. but today I read an article from Science Daily that contradicts ...
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183 views

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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How do EM waves cause molecules to rotate, move, and cause electrons to move up energy levels?

Atoms can absorb electromagnetic waves to cause electrons to jump up energy levels, when electrons go down energy levels they release a photon. But how do EM waves cause atoms to rotate, and vibrate?
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61 views

Electron's Energy In The Atom

I know that the exact (OK most of the times not the exact) energy of an electron can be calculated by solving Schrodinger's differential equation, but can we explain an electron's energy of a specific ...
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Why does the first lithium stationary state have n = 9/4?

The ionization energy of $\ce{He+}$ is $19.6 \times 10^{-18}~\mathrm{J~atom^{-1}}$. What is the energy of the first stationary state ($n=1$) of $\ce{Li^{2+}}$? Since the question specifically states ...
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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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1answer
972 views

Definition of relative atomic mass

I found out there are two definitions of relative atomic mass $A_\mathrm r$. First definition is $A_\mathrm r$ is the mass of 1 atom of an element relative to 1/12 the mass of carbon-12 atom. It can ...
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2answers
1k views

Calculating Avogadro's Number

For a school project, I am in a group tasked with calculating Avogadro's Number in multiple manners. Other than the Millikan Oil Drop Experiment, we know of no ways to compute it. A Google search ...
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1answer
147 views

Photoelectric effect and electron loss

I've read that when a certain amount of UV light is shone on a metal surface, electrons are ejected (the photoelectric effect). Are these electrons from the metal atoms themselves? and in case they ...
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1answer
553 views

Placing the atomic mass and number of an element... [closed]

Why are the atomic and the mass numbers of an element flipped in the textbooks relative to the periodic table?
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1answer
135 views

Atomic number $Z$

If electrons were spin-$\frac {3}{2}$ instead of spin-$\frac {1}{2}$ , what would be the atomic number $Z$ for the first noble gas ?
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1answer
2k views

Electron Configuration of an element with no. of electrons > 18

Let's say that we have an element, say $\ce{Ca}$. According to law, the last shell should contain only upto 8 e-. Hence, electronic configuration of $\ce{Ca}$ would be 2,8,8,2. But, according to the ...
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207 views

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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82 views

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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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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739 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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205 views

How to determine the permissible values for which solution of the Schrödinger's wave equation exists?

My textbook( A Textbook of Physical Chemistry, Dr. O.P. Tandon ) says that solution of the Schrödinger's wave equation exists only for certain permissible values which are called eigen values.( ...
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199 views

Why are Bohr's formulae for radius and velocity still in use when Heisenberg's uncertainty principle predicts otherwise?

I learnt about Heisenberg's Uncertainty principle which states that it is not possible to determine the position and momentum of a small particle at the same time. I was told that it is because in ...
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Few basic questions about ionic bonding and batteries (lead)

I've got a few very very basic questions about ionic bonds and their role in batteries. My assumptions (correct me if I'm wrong): Ionic bonds occur between a metal and a non-metal (the non-metal ...
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134 views

Is there an algorithm for ascertaining the relative size of an atomic/ionic radius?

To the best of my knowledge, the following properties affect atomic radius. The grounded-state size of the valence electron shell. The Coulomb force of the core electrons less the Coulomb force of ...
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272 views

First ionization energy of hydrogen molecule

If we have the dissociation's energies of hydrogen molecule $\ce{H_{2}}$($D_{0}$) and the corresponding molecule ion $\ce{H_{2}^{+}}$ ($D_{1}$) together with the first energy of ionization of hydrogen ...
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2k views

Magnetic moment of coordination complexes?

To understand the commonly quoted magnetic values of coordination complexes (central ion) we use $$m_l=\sqrt{n(n+2)} \text{BM where BM}=\frac{e\hbar}{2m_e}\text{JT}^{-1}$$ $n$=number of unpaired ...
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230 views

Spin quantum number of electron

Why is the spin quantum number of an electron +1\2 or -1\2 in an atom? Is this an experimental value or theoretical value?
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1answer
21k views

How many valence electrons does a copper atom have? [duplicate]

The valence electron configuration of $\ce{Cu}$ is $\ce{4s^1 3d^{10}}$. According to this the answer is $11$, but shouldn't it be $1$ since the d shell is already filled up?
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1answer
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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3answers
4k views

How can the number of molecules and atoms be the same in a gas?

A sample of certain mass of gas was collected and it was found that the number of atoms and the number of molecules in the collected sample are equal. You are required to state the conclusion drawn ...
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2answers
189 views

How will these hydrogen atoms interact?

Assume that we have a space with just two $\ce{H}$ atoms and their distance to each other is $d$. Let's say they don't have initial velocity. What is the force with which they will act on each other? ...
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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
785 views

Wasn't Rutherford's assumption of gold foil to be made of single layer wrong?

My teacher taught about Rutherford's gold foil experiment today. Sir said that, Rutherford used gold foil of thickness $10^{-7}$ m and concluded atom to be of size $10^{-10}$ m. Sir also said that ...
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1answer
99 views

How did scientists discover the concepts of anode and cathode without knowing about electrons? [closed]

Scientists researched electrons and came to know about electrons after the battery was developed as we can see in the JJ Thomson's model that he used the cathode and anode. My question is that that if ...
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5answers
467 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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2answers
5k views

Calculating the number of neutrons in a sample

Which of the following contains one mole of neutrons? A. $\pu{1 g}$ of $\ce{^1_1H}$ B. $\pu{1 g}$ of $\ce{^{12}_6C}$ C. $\pu{2 g}$ of $\ce{^{24}_{12}Mg}$ D. $\pu{2 g}$ of $\ce{^{23}_{10}Ne}$ Here's a ...
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13k views

How many electrons can each shell in an atom hold?

I know that the first shell can hold up to 2, the second and third can hold up to 8, and the fourth 18. But what about after that?
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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
259 views

Why is there no electron swapping after excitation?

If we have 2 electrons in the 1st energy level named X & Y, and one electron in the 2nd energy level named Z. If the electron X was excited and transferred to the higher energy level, why didn't ...
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1answer
64 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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1answer
1k views

How are the molar mass and molecular mass of any compound numerically the same?

This observation is really annoying me, and the internet isn't providing me with any solid answers. Either their definitions of molar mass completely differ, or they don't stick to their own ...
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1answer
1k views

Greater entropy: an atom or macromolecule?

A question that appeared on my last chemistry exam was : Which of the following has greater entropy A) An atom B) A macromolecule The question doesn't specify anything else(i.e. type/size of ...
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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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1answer
345 views

Does dilithium exist? [duplicate]

Lithium has two electrons in $\mathrm{1s}$, filling the first energy level; and one valence electron in $\mathrm{2s}$. Could two $\ce{Li}$ atoms form a bond to create $\ce{Li2}$; like $\ce{O2}$ or $\...

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