Question

During $ẞ^{-}$ decay of a radioactive element there is an increase in its

• A. proton number
• B. mass number
• C. neutron number
• D. atomic weight
• E. electron number

Answer 1

The Correct Option is A

Beta Minus Decay

We want to determine what increases during \( \beta^- \) decay of a radioactive element.

Step 1: Understanding Beta Minus Decay

In \( \beta^- \) decay, a neutron within the nucleus is converted into a proton, an electron (the \( \beta^- \) particle), and an antineutrino. The electron and antineutrino are emitted from the nucleus.

\( n \rightarrow p + e^- + \bar{\nu}_e \)

Step 2: Effects on Atomic Numbers

Mass Number (A): The mass number is the total number of protons and neutrons in the nucleus. Since a neutron is converted into a proton, the total number of nucleons (protons + neutrons) remains the same. The Mass number stays constant. 
Atomic Number (Z): The atomic number is the number of protons in the nucleus. Since a neutron is converted into a proton, the atomic number increases by one. 
Neutron Number (N): The number of neutrons decreases by one.

Step 3: Atomic Number and Proton Number

The atomic number is the same as the proton number. Therefore, during beta-minus decay, the proton number increases.

Conclusion

During \( \beta^- \) decay of a radioactive element, there is an increase in its proton number (atomic number).

Answer 2

Concept: In a β⁻ (beta minus) decay, a neutron inside the nucleus is converted into a proton, and an electron (β⁻ particle) is emitted: \[ n \rightarrow p + e^- \]

Step 1: Since a neutron becomes a proton: 

• Mass number remains the same (1 neutron → 1 proton)
• Proton number increases by 1
• Neutron number decreases by 1

Final Answer: proton number