Chemistry ยท 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

Which of the following statements is/are correct?

(a). Naturally occurring oxygen is a mixture of atoms of slightly different masses called isotopes. (b). Formula mass and not molecular mass is used for a substance whose constituent particles are ions. (c). Basic radicals carry negative charge.

  1. (a) only

  2. (b) only

  3. (c) only

  4. (a) and (b)

  5. (b) and (c)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the correct answer as both these statements are correct.

Multiple choice

The atomic no. of carbon is

  1. 6

  2. 7

  3. 8

  4. 9
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The atomic number of carbon is 6, which means it has 6 protons in its nucleus. This also means it has 6 electrons in a neutral atom, arranged as 2,4 in electron shells (K and L shells).

Multiple choice

The atoms of different element which have the same mass number but different atomic number are called

  1. Isotopes

  2. Isobars

  3. Isotones

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Isobars are atoms of different elements with the same mass number but different atomic numbers. This means they have the same total number of nucleons (protons + neutrons) but different numbers of protons. For example, 40Ar (Argon, Z=18) and 40Ca (Calcium, Z=20) are isobars. Isotopes have the same atomic number but different mass numbers, while isotones have the same number of neutrons.

Multiple choice

The ground state free ion term of V2+ for weak field ligand is ________.

  1. 3D3/2

  2. 3F3/2

  3. 4D3/2

  4. 4F3/2

  5. 4F9/2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

V2+ has d3 electronic configuration and it is empowered in a weak field ligand. The term symbol is calculated by the formula- 2s+1 LJ For d3, n = 3 s = n/2 = 3/2 2s + 1 = 4 L = 3 = F J = (L + s) to (L - s) = 2, 1, 0 term symbols = 2s + 1 LJ = 4F9/2, 4F7/2, 4F5/2, 4F3/2 The ground state term for V2+ is 4F3/2.

Multiple choice

The ground state term symbols of Fe3+ and Fe2+ in a high spin ligand system are __________.

  1. 6S5/2 and 5D4

  2. 6S3/2 and 5D3

  3. 5S5/2 and 5D4

  4. 6S3/2 and 4D3/2

  5. 6S5/2 and 5D3/2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fe3+ and Fe2+ have d5 and d6 electronic configurations and both are in high spin ligand system. The term symbol is calculated by the formula- 2s+1 LJ For d5, n = 5 s = n/2 = 5/2 2s + 1 = 6 L = 0 = S J = (L + s) to (L - s) = 5/2 Possible term symbol for Fe3+ = 2s + 1 LJ = 6S5/2 Similarly, possible term symbols for Fe2+ = 5D4, 5D3, 5D2, 5D1, 5D0 The ground state term for Fe3+ is 6S5/2. The ground state term for Fe2+ is 5D4.

Multiple choice

Atomic number of a light element = _____________ = ______________.

  1. atomic mass and number of electrons

  2. number of electrons and number of protons

  3. protons and neutrons

  4. atomic mass and number of neutrons

  5. number of electrons and number of neutrons
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, atomic number of a light element is equal to the number of electrons and also number of protons.

Multiple choice

The atomic number of Li is

  1. 4

  2. 3

  3. 6

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

The atomic number of Lithium (Li) is 3, which means it has 3 protons in its nucleus. This places it as the third element in the periodic table, after Hydrogen (1) and Helium (2).

Multiple choice

Which of the following sets represents only diamagnetic ions?

  1. Cu2+, Zn2+, Sc3+

  2. Zn2+, Sc3+, Ti4+

  3. Cu+, Mn2+, Cr3+

  4. Ni2+, Cu2+, Zn2+

  5. Cu+, Mn2+, Sc3+
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Zn2+: [Ar] 3d10 4s0; no unpaired electron; diamagnetic Sc3+: [Ar] 3d0 4s0; ; no unpaired electron; diamagnetic Ti4+: [Ar] 3d0 4s0; no unpaired electron; diamagnetic

Multiple choice

Isotopes differ in

  1. atomic number

  2. mass number

  3. number of protons

  4. number of electrons
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Isotopes are variants of a particular chemical element which differ in the mass number, although all isotopes of a given element have the same number of protons in each atom.