As you move down the periodic table, atomic size increases (due to the number of electron shells of an atom increasing). So in Group 1, H has the smallest atomic size, while Fr has the largest.
Ionization energy tends to decrease as you go down a group, and increase as you go from left to right on the periodic table. (As you go down, the atomic size/radius increases, so the outermost electrons are held less tightly to the nucleus, causing a lower ionization energy.)
Electronegativity relates to ionization energy. Elements with a higher ionization energy will have higher electronegativity. Therefore, as you move down the periodic table, electronegativity decreases, while as you move from left to right on the periodic table, electronegativity increases.
