Question

A nucleus $\underset{11}{24}Na$ is $\beta$-radioactive. What are the numbers $24$ and $11$ called?

• A. 24 - atomic number, 11 - mass number
  
• B. 24 - mass number, 11 - atomic number
  
• C. 24 - electron number, 11 - atomic number
  
• D. 24 - mass number, 11 - nuetron number
  

Answer 1

The correct option is B 24 - mass number, 11 - atomic number

Here, $24$ is called the mass number while $11$ is called the atomic number.