Periodic Trends

Atomic radius generally increases down a group and decreases across a period. Rb is in the same group as Li, Na, and K, and it is the lowest in the group, so it has the largest atomic radius.

Ionization energy generally increases across a period and decreases down a group. F is in the same period as Cl, Br, and I, and it is the furthest to the right in the period, so it has the highest ionization energy.

Electron affinity generally becomes more negative across a period and less negative down a group. O is in the same period as S, Se, and Te, and it is the furthest to the right in the period, so it has the most negative electron affinity.

Electronegativity generally increases across a period and decreases down a group. F is in the same period as Cl, Br, and I, and it is the furthest to the right in the period, so it is the most electronegative.

Metallic character generally increases down a group and decreases across a period. Rb is in the same group as Li, Na, and K, and it is the lowest in the group, so it is the most metallic.

Nonmetallic character generally increases across a period and decreases down a group. F is in the same period as Cl, Br, and I, and it is the furthest to the right in the period, so it is the most nonmetallic.

Melting point generally decreases down a group and increases across a period. He is in the same period as Ne, Ar, and Kr, and it is the furthest to the left in the period, so it has the lowest melting point.

Boiling point generally increases down a group and decreases across a period. Te is in the same group as O, S, and Se, and it is the lowest in the group, so it has the highest boiling point.

Density generally increases down a group and across a period. Os is in the same period as Ir, Pt, and Au, and it is the furthest to the left in the period, so it is the most dense.

Density generally increases down a group and across a period. Li is in the same group as Na, K, and Rb, and it is the highest in the group, so it is the least dense.

Reactivity generally increases down a group and decreases across a period. Li is in the same group as Na, K, and Rb, and it is the highest in the group, so it is the most reactive.

Reactivity generally increases down a group and decreases across a period. He is in the same period as Ne, Ar, and Kr, and it is the furthest to the left in the period, so it is the least reactive.

Elements in the leftmost column of the periodic table are most likely to form cations. Li is in the leftmost column, so it is the most likely to form a cation.

Elements in the rightmost column of the periodic table are most likely to form anions. F is in the rightmost column, so it is the most likely to form an anion.

Elements in the middle of the periodic table are most likely to form covalent bonds. C is in the middle of the periodic table, so it is the most likely to form a covalent bond.