How does the radioactive isotope c-14 differ from its stable counterpart c-12?

Isotope  is defined as atom of same element with same atomic number but different mass number.

Here, atomic number for C-14 and C-12  is 6 but mass number is 14 and 12 respectively.

Atomic number is equal to number of protons and electrons in an atom and mass number is equal to sum of number of protons and neutrons in nucleus of an atom.

Since, both have same atomic number, the number of protons will be 6 for both but they have different number of neutrons.

Number of neutrons in C-12:

Number of neutrons in C-14:

The number of neutrons in C-12 is 6 and that in C-14 is 8. Therefore, isotope C-14 differ from the stable C-12 in number of neutrons.

1.solid

2.carbon dioxide

3.helium

the answer is na (sodium)