Chemistry 9th Chap 3 : Topic 10 - Maryam Publications

Chemistry Chapter 3 : Topic 10

Mass Number

1 / 10

An atom of an element contains 11 protons, 12 neutrons, and 11 electrons. When calculating its nucleon number, only the nucleus is considered because electrons have negligible mass. What will be the nucleon number of this atom?

A) 33

B) 23

C) 11

D) 12

2 / 10

A student states that atomic mass of an atom is determined only by protons because neutrons have no charge. This statement is incorrect because atomic mass depends on particles present in the nucleus. What is the correct interpretation?

A) Only protons contribute to atomic mass

B) Only neutrons contribute to atomic mass

C) Both protons and neutrons contribute to atomic mass

D) Electrons contribute equally to atomic mass

3 / 10

An isotope of carbon has 6 protons and 8 neutrons. Even though it behaves chemically like carbon, its mass is different due to nuclear composition. What is its nucleon number?

A) 8

B) 14

C) 12

D) 6

4 / 10

Two atoms have the same number of protons but different numbers of neutrons. This difference affects their mass but not their chemical properties. What causes this difference in nucleon number?

A) Different number of energy levels

B) Different electrons in outer shell

C) Different chemical bonding

D) Different number of neutrons in nucleus

5 / 10

A nucleus contains 17 protons and 18 neutrons. A student incorrectly includes electrons in nucleon number calculation. Why is this incorrect?

A) Electrons are outside nucleus and have negligible mass

B) Electrons determine chemical mass

C) Electrons are part of nucleus but unstable

D) Electrons are heavier than protons

6 / 10

An element has nucleon number 40 and contains 20 protons. A student is asked to determine the number of neutrons. What is the correct reasoning process?

A) Multiply protons by neutrons

B) Subtract protons from nucleon number

C) Subtract nucleon number from protons

D) Add protons and electrons

7 / 10

In nuclear notation, an element is written as X with mass number 56 and atomic number 26. A student concludes that neutrons are 30. What concept justifies this calculation?

A) Neutrons = atomic number + mass number

B) Neutrons = protons × electrons

C) Neutrons = electrons - protons

D) Neutrons = mass number - atomic number

8 / 10

Two isotopes of chlorine have nucleon numbers 35 and 37. They behave similarly in chemical reactions because their electron configuration is the same. What causes the difference in their mass?

A) Different number of protons

B) Different number of electrons

C) Different number of neutrons

D) Different valency

9 / 10

A nucleus is described as the dense central part of an atom containing almost all its mass. Which statement best supports this?

A) Protons and neutrons are located in nucleus and determine mass

B) Neutrons have no mass

C) Electrons are heavier than nucleons

D) Electrons contribute most of the mass

10 / 10

A student compares two atoms: one has 12 protons and 12 neutrons, and the other has 12 protons and 14 neutrons. They conclude that both have same chemical behavior but different nucleon numbers. What is the correct interpretation?

A) Same element, different isotopes with different mass

B) Different elements with same mass

C) Both have same nucleon number

D) Both atoms are different elements

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