Trends in the Periodic Table

Trends in Mass

• As you move from left to right across a period, mass increases

• As you move from top to bottom down a group, mass increases

• Masses get larger in both these cases as the atoms have more protons, neutrons and electrons

Trends in Atomic Radius

• As you move from left to right across a period atomic radius DECREASES!!

– This is because the electrons are “pulled in” closer to the nucleus as the number of protons increases….the atom “shrinks” in a bit.

– See graph on p. 23

Trends in Atomic Radius

• As you move from top to bottom down a group, atomic radius INCREASES as the atoms have more electron shells.

Trends in Reactivity for Metals

• As you move from left to right across a period, reactivity decreases for metals

• As you move from top to bottom down a group, reactivity increases for metals

The most reactive metal is francium (Fr)

Trends in Reactivity for Non-metals

• As you move from left to right across a period, reactivity for non-metals increases

• As you move from top to bottom down a group, reactivity for non-metals decreases.

• Remember the noble gases are NON-REACTIVE, so the most reactive non-metal is fluorine (F)

Trends in Ionization Energy

• Ionization energy is the energy required to remove the outermost electron from an atom

• Ionization energy increases across a period and decreases down a group

Trends in Ionization Energy