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Chapter: 9th Science : Chemistry : Atomic Structure

One Mark Questions Answers

Science : Chemistry : Atomic Structure : Book Back Important Questions, Answers, Solutions : I. Choose the correct answer, II. Fill in the blanks, III. State whether true or false. If false, correct the statement, IV. Match the following, V. Assertion and reason type questions





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 :

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