Among the elements of the main group, the first ionization energy increases from left to right across a period.
from right to left across a period.
when the atomic radius increases.
down a group.

ljjjljlj kjlk,ljym jlyu; jm; l mumytj

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.