1. Periodic Trends
SCH3U
Ms. Richardson

2. Atomic Radius Size of an atom
Distance between the nuclei of two bonded atoms

3. Atomic Radius Affected by : a change in n:
As n increases down a group, electrons are more likely to be found further from their nucleus
n increases, atomic radii increase
effective nuclear charge (Zeff)
The net force of attraction between electrons and the nucleus they surround
As Zeff increases across a period, electrons experience a reduced force of attraction
Zeff increases, atomic radii decrease

4. Ionization Energies
The energy needed to completely remove one electron from a ground state gaseous electron

5. Ionization Energies Generally decrease down a group
Less force of attraction between nucleus and valence electrons
Increase across a period
Increased force of attraction between nucleus and valence electrons

6. Ionization Energies
Reaction
With air (oxygen)
With water
With acid
Group 1
Reacts rapidly to form oxides
Reacts vigorously to form base and H2
Reacts violently to form H2
Group 2
Reacts moderately to form oxides
Reacts slowly to form base and H2
Reacts quicky to form H2
Group 13
Reacts slowly to form oxides
Displaces H2
Reacts readily to form H2
Group 14
Form acidic oxides
Sn and Pb don’t react
Sn and Pb react slowly
Transition metals
Zn is most reactive
Zn and Fe displace H2
Zn reacts readily
Trends are linked to trends in reactivity of metals
Reactivity increases down a group and decreases across a period

7. Electron Affinity
Change in energy that occurs when an electron is added to a gaseous atom
Positive values – energy is required to add electron
Negative values – energy is released when electron is added
Low positive & low negative numbers = low electron affinity