Structure of Atom

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

(a) 3, 8, 1

(b) 2, 8, 2

(c) 1, 8, 3

(d) 8, 2, 2

• a

• b

• c

• d

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

(a) electron

(b) proton

(c) nucleus in the atom

(d) atomic mass

• a

• b

• c

• d

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

• (i) and (ii)

• (i) and (iii)

• (ii) and (iii)

• (ii) and (iv)

Which of the following statement is always correct?

• (a) An atom has equal number of electrons and protons.

• (b) An atom has equal number of electrons and neutrons.

• (c) An atom has equal number of protons and neutrons.

• (d) An atom has equal number of electrons, protons and neutrons.

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

• 5

• 8

• 12

• 18

An alpha particle is also known as:

(a) subatomic particle

(b) an unionised helium atom

(c) a neutral particle

(d) a doubly-charged helium ion

• a

• b

• c

• d

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

(a) P-32

(b) I-131

(c) Co-60

(d) C-14

• a

• b

• c

• d

Isobars do not differ in the number of

(a) protons

(b) electrons

(c) neutrons

(d) nucleons

• a

• b

• c

• d

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?

(a) 13

(b) 10

(c) 14

(d) 16

• a

• b

• c

• d

The electronic configuration of an element is 2,8,5. What is its valency?

• 1

• 2

• 3

• 4