Which of the following statements is true? ca does not react with other atoms because it has 8 electrons in its outermost shell. mg does not react with other atoms because its outermost shell is complete. ca is more reactive than k because ca has to lose one more electron than k to complete its outermost shell. mg is less reactive than na because mg has to lose one more electron than na to complete its outermost shell.

The last statement is true. which is:

Mg is less reactive than Na because Mg has to lose one more electron than Na to complete its outermost shell.

Mg belongs to group II and Na belongs to group I.

Group II elements are less reactive than Group I elements. This is because it is more difficult to lose two electrons compared to losing just one electron.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.