Periodic Trends The physical and chemical properties of the elements are periodic functions of their atomic numbers.

Atomic Radius Distance between the radii of two atoms

Trends in the periodic table: Atomic radius Radius DECREASES as you go left to right across a period.

Going across the period Electrostatic attraction increases. Electrons are pulled closer to the nucleus. Valence electrons are more tightly held.

Trends in the periodic table: Atomic radius Radius INCREASES as you down a group.

Going down a group Orbitals are larger. Electrons are farther from the nucleus. Valence electrons are less tightly bound.

Ionization Energy Amount of energy required to remove an electron from the ground state of a gaseous atom or ion. First ionization energy is that energy required to remove the first electron. Second ionization energy is that energy required to remove the second electron, etc.

Ionization Energy It requires more energy to remove each successive electron. When all valence electrons have been removed, the ionization energy takes a quantum leap.

Trends in First Ionization Energies As one goes down a column, less energy is required to remove the first electron.

Trends in First Ionization Energies Generally, as one goes across a row, it gets harder to remove an electron.

Electronegativity The tendency of an atom to attract electrons to itself when combined with another element. It increases going left to right across a period. It decreases going down a group.

Electronegativity