One Mark Questions Answers

CHEMISTRY

ATOMIC STRUCTURE

TEXT BOOK EXERCISES

I. Choose the correct answer :

1. Among the following the odd pair is

(a) ¹⁸₈O, ¹⁹₉F

(b) ⁴⁰₁₈Ar, ¹⁴₇N

(c) ³⁰₁₄Si, ³¹₁₅P

(d) ⁴⁰₂₀Cr, ³⁹₁₉K

 [Answer: (b) ⁴⁰₁₈Ar, ¹⁴₇N]

2. Change in the number of neutrons in an atom changes it to

(a) an ion.

(b) an isotope.

(c) an isobar.

(d) another element.

[Answer: (b) an isotope]

3. The term nucleons refer to

(a) protons and electrons

(b) only neutrons

(c) electrons and neutrons

(d) protons and neutrons

[Answer: (d) protons and neutrons]

4. The number of protons, neutrons and electrons present respectively in ⁸⁰₃₅Br are

(a) 80, 80, 35

(b) 35, 55, 80

(c). 35, 35, 80

(d) 35, 45, 35

[Answer: (d) 35, 45, 35]

5. The correct electronic configuration of potassium is

(a) 2,8,9

(b) 2,8,1

(c) 2, 8, 8, 1

(d) 2, 8, 8, 3

[ Answer: (c) 2, 8, 8, 1]

II. State true or false. If false, correct the statement:

1. In an atom, electrons revolve around the nucleus in fixed orbits.

Answer: True.

2. Isotopes of an element have different atomic numbers.

Answer: False.

Correct statement: Same atomic numbers but different mass numbers.

3. Electrons have negligible mass and charge.

Answer: True.

4. Smaller the size of the orbit, lower is the energy of the orbit.

Answer: True.

5. The maximum number of electron in L Shell is 10.

Answer: False.

Correct statement : The maximum number of electrons in L Shell is 8.

III. Fill in the blanks :

1. Calcium and Argon are examples of a pair of isobars.

2. Total number of electrons that can be accommodated in an orbit is given by the formula 2n².

3. Uranium-235 isotope is used in the nuclear reactors.

4. The number of neutrons present in ₃⁷Li is 4 _.

5. The valency of Argon is Zero_.

IV. Match the following :

a) Dalton - 1. Hydrogen atom model

b) Chadwick - 2. Discovery of nucleus

c) Rutherford - 3. First atomic theory

d) Neils Bohr - 4. Plum pudding model

 5. Discovery of neutrons

Answer: a - 3, b - 5, c - 2, d - 1.

a) Dalton - First atomic theory

b) Chadwick - Discovery of neutrons

c) Rutherford - Discovery of nucleus

d) Neils Bohr - Hydrogen atom model

V. Complete the following table :