R4RIN – MCQs, Mock Tests | NCERT Class 9 Class 9 Science Chapter 4 Structure of the Atom

Which of the following correctly represents the electronic distribution in the Mg atom?

1. 3, 8, 1
2. 2, 8, 2
3. 1, 8, 3
4. 8, 2, 2

✅ Correct Answer: 2

Rutherford’s ‘alpha (α) particles scattering experiment’ resulted in the discovery of

1. electron
2. proton
3. nucleus in the atom
4. atomic mass

✅ Correct Answer: 3

Which of the following are true for an element? (i) Atomic number = number of protons + number of electrons (ii) Mass number = number of protons + number of neutrons (iii) Atomic mass = number of protons = number of neutrons (iv) Atomic number = number of protons = number of electrons

1. (i) and (ii)
2. (i) and (iii)
3. (ii) and (iii)
4. (ii) and (iv)

✅ Correct Answer: 4

Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order (i) Rutherford’s atomic model (ii) Thomson’s atomic model (ii) Bohr’s atomic model

1. (i), (ii) and (iii)
2. (ii), (iii) and (i)
3. (ii), (i) and (iii)
4. (iii), (ii) and (i)

✅ Correct Answer: 3

The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

1. 13
2. 10
3. 14
4. 16

✅ Correct Answer: 2

The first model of an atom was given by

1. N. Bohr
2. E. Goldstein
3. Rutherford
4. J.J. Thomson

✅ Correct Answer: 4

An atom with 3 protons and 4 neutrons will have a valency of

1. 3
2. 7
3. 1
4. 4

✅ Correct Answer: 3

Which of the following statement is always correct?

1. An atom has equal number of electrons and protons.
2. An atom has equal number of electrons and neutrons.
3. An atom has equal number of protons and neutrons.
4. An atom has equal number of electrons, protons and neutrons.

✅ Correct Answer: 1

Which of the following statements about Rutherford’s model of atom are correct? (i) Considered the nucleus as positively charged. (ii) Established that the a-particles are four times as heavy as a hydrogen atom. (iii) Can be compared to solar system. (iv) Was in agreement with Thomson’s model.

1. (i) and (iii)
2. (ii) and (iii)
3. (i) and (iv)
4. only (i)

✅ Correct Answer: 1

How many electrons are present in M-shell of an element with atomic number 20?

1. 5
2. 8
3. 12
4. 18

✅ Correct Answer: 2

An alpha particle is also known as:

1. subatomic particle
2. an unionised helium atom
3. a neutral particle
4. a doubly-charged helium ion

✅ Correct Answer: 4

The charge on an electron is equal to:

1. 1.6 × 10-19 C of -ve charge
2. 2.6 × 10-19 C of -ve charge
3. 1.6 × 10-22 C of -ve charge
4. 1.6 × 10-23 C of -ve charge

✅ Correct Answer: 1

Which of the following isotope is used in the treatment of blood cancer?

1. P-32
2. I-131
3. Co-60
4. any of these

✅ Correct Answer: 1

Isobars do not differ in the number of

1. protons
2. electrons
3. neutrons
4. nucleons

✅ Correct Answer: 4