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 atomic weight of an element is 52 and the atomic number is 24. The number of electrons, protons and neutrons in an atom of this element will be, respectively,

  1. 24, 24 and 28

  2. 24, 28 and 24

  3. 28, 24 and 24

  4. 52, 24 and 28
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Atomic number = Number of electrons = Number of protons Atomic weight = Number of protons + Number of neutrons The number of electrons, protons and neutrons in an atom of this element will be, respectively, 24, 24 and 28

Multiple choice

Write no. of protons in carbon?

  1. 7

  2. 6

  3. 9

  4. 8
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The atomic number of carbon is 6, which indicates that a neutral carbon atom has 6 protons in its nucleus.

Multiple choice

In case of the triad containing the elements Ba, Ca and Sr, which of the following statements is correct?

  1. The atomic mass of Ba is roughly the average of the atomic masses of the other two elements.

  2. The atomic mass of Sr is roughly the average of the atomic masses of the other two elements.

  3. The atomic mass of Ba is less than the average of the atomic masses of the other two elements.

  4. The atomic mass of Sr is more than the average of the atomic masses of the other two elements.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to the definition of Dobereiner's law of triads, (the atomic mass of the middle element was roughly the average of the atomic masses of the other two elements) the statement (2) is correct.  

Multiple choice

Which elementary particles are equal in mass?

  1. Neutron & proton

  2. electron & proton

  3. neutron & electron

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Protons and neutrons are both nucleons and have nearly identical masses, approximately 1 atomic mass unit each, whereas electrons are significantly lighter.