Chemistry · Physics

Atomic Structure and Mass

308 Questions

Atomic structure and mass focus on the composition of atoms, including protons, neutrons, electrons, and isotopes. This topic is essential for the chemistry sections in engineering and civil services competitive exams. Review these questions to practice calculating atomic mass, neutron count, and isotopic distributions.

Atomic mass unit calculationsNeutron and proton countsIsotopic distribution averagesLaw of triadsRest energy of atoms

Atomic Structure and Mass Questions

Multiple choice

The number of protons in the nucleus of an atom.

  1. Atomic Number

  2. Atomic Nucleus

  3. Atomic Mass Number

  4. Electron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The atomic number is the number of protons found in the nucleus of every atom of an element. It uniquely identifies a chemical element.

Multiple choice physics static electricity properties of charges charge properties of charge

A copper slab of mass $2 g$ contains $2 \times 10^{22}$ atoms. The charge on the nucleus of each atom is $29 e$. What fraction of the electrons must be removed from the sphere to give it a charge of $+2\mu C$? 

  1. $58 \times 10^{22}$
  2. $1.25 \times 10^{13}$
  3. $2.16 \times 10^{11}$
  4. $2.16 \times 10^{-11}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Given a mass of copper slab $=2\, g$ contains $2\times 10^{22}$ atoms.
Charge on nucleus of each atom $=29e$
We have to find the fraction of electrons that must be removed from sphere to give it $+2\mu C$ charge.
We solve it as follows:
Total number of electrons in sphere $=29\times 2\times 10^{22}$
Number of electrons $=\dfrac qe$
$=\dfrac{2\times 10^{-6}}{1.6\times 10^{-19}}$
$=1.25\times 10^{13}$
Fraction of electrons removed $=\dfrac{1.25\times 10^{13}}{Total\; number \; of \;electrons \; in\; sphere}$
$=\dfrac{1.25\times 10^{13}}{29\times 2\times 10^{22}}$
$=2.16\times 10^{-11}$
Multiple choice

What is the current best estimate of the electron neutrino mass?

  1. Less than 1 electronvolt

  2. Between 1 and 10 electronvolts

  3. Between 10 and 100 electronvolts

  4. More than 100 electronvolts
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The current best estimate of the electron neutrino mass is less than 1 electronvolt, based on measurements from the KATRIN Experiment.

Multiple choice

What is the mass of a neutrino?

  1. 0

  2. Very small but non-zero

  3. Unknown
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The mass of a neutrino is very small, but it is not zero. The exact mass values of different neutrino types are still being studied and are subject to ongoing research.

Multiple choice

The mass of an atom is mostly concentrated in its:

  1. Electrons

  2. Protons

  3. Neutrons

  4. Quarks

  5. Photons
Reveal answer Fill a bubble to check yourself
Correct answer
Explanation

The mass of an atom is mostly concentrated in its protons and neutrons.

Multiple choice

What is the mass of the Higgs boson?

  1. 125 GeV/c^2

  2. 175 GeV/c^2

  3. 200 GeV/c^2

  4. 225 GeV/c^2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The mass of the Higgs boson is 125 GeV/c^2.

Multiple choice

What is the approximate mass of an electron neutrino?

  1. Less than 1 electronvolt

  2. Between 1 and 10 electronvolts

  3. Between 10 and 100 electronvolts

  4. Greater than 100 electronvolts
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The exact mass of the electron neutrino is still unknown, but it is estimated to be less than 1 electronvolt.

Multiple choice

What is the GUT prediction for the ratio of the masses of the proton and the electron?

  1. 1/1836

  2. 1/1000

  3. 1/100

  4. 1/10
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

GUTs predict that the ratio of the masses of the proton and the electron is approximately 1/1836.

Multiple choice

What is the atomic number of an element?

  1. Number of protons in the nucleus

  2. Number of neutrons in the nucleus

  3. Number of electrons in the nucleus

  4. Number of electrons in the outermost shell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The atomic number of an element is equal to the number of protons in the nucleus of its atoms.