What is a solution? A. A mixture of two solids blended together
B. A compound that is in liquid and gas states
C. A liquid with something dissolved in it
OD. A clear liquid with nothing dissolved in it

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.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.