Chemistry 9th Chap 3 : Topic 9 - Maryam Publications

Chemistry Chapter 3 : Topic 9

Radioactivity and Element Identity

1 / 10

Radioactivity is a natural nuclear process in which unstable atomic nuclei emit particles or energy. During certain types of radioactive decay, the nucleus undergoes a transformation that may change the proton number. What is the main consequence of a change in proton number?

A) The atom transforms into a completely different element

B) The atom’s chemical identity remains unchanged

C) The atom becomes an isotope of the same element

D) Only the mass number changes, not the element

2 / 10

During alpha decay, a nucleus emits an alpha particle consisting of 2 protons and 2 neutrons. How does this affect the original atom?

A) Neutron number remains unchanged

B) Proton number decreases by 2, changing the element

C) Proton number increases by 2

D) Only electrons are lost

3 / 10

An unstable nucleus undergoes beta decay in which a neutron is converted into a proton. What is the most important result of this change?

A) The nucleus becomes stable immediately in all cases

B) The atom remains the same element

C) The proton number increases, forming a new element

D) The mass number decreases by 1

4 / 10

A scientist observes that after radioactive decay, the atomic number of an element changes from 92 to 90. What conclusion is correct?

A) The element has changed into a different element

B) Only neutrons were added

C) Only electrons were lost

D) The element remains uranium

5 / 10

Which statement best explains why radioactivity can lead to element transformation?

A) Because proton number is changed during nuclear decay

B) Because electrons control nuclear stability

C) Because neutrons define chemical properties

D) Because atoms always lose mass in reactions

6 / 10

A nucleus emits gamma radiation without losing any particles. What is the effect on the atomic identity of the element?

A) Neutron number becomes zero

B) Proton number decreases

C) It changes into a new element

D) No change in proton number or element identity

7 / 10

Which type of radioactive decay directly decreases the proton number of an atom?

A) Beta decay

B) Electron emission only

C) Alpha decay

D) Gamma decay

8 / 10

A student claims: “Radioactivity only changes the physical state of an atom, not its identity.” Why is this incorrect?

A) Because radioactivity changes electrons only

B) Because neutrons determine identity

C) Because nuclear changes can alter proton number

D) Because atoms cannot decay naturally

9 / 10

In a nuclear reaction, an atom of element X changes its proton number from 15 to 16. What is the correct interpretation?

A) Only chemical properties change, not identity

B) The atom becomes neutral

C) Only isotopic change occurs

D) Element X becomes a different element

10 / 10

Why is radioactivity considered a nuclear-level change rather than a chemical change?

A) Because it affects the nucleus and may change proton number

B) Because it involves rearrangement of electrons only

C) Because it always produces gases

D) Because it occurs only in compounds

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