Periodic Trends

Atomic Radius Atomic Radius is defined as half the distance between the center of 2 atoms of the same element just touching each other. The radius decreases going across a period and increases going down a group.

Why Atomic Radius Trends Why are atoms Larger Going down a group? Atoms are larger because the higher the energy level, the more orbitals it has, and the larger the orbitals get. Why do atoms get smaller going from left to right across the table? 1st increase in the nuclear charge (more protons) 2nd lack of shielding from completed orbitals. Core electrons block the attraction between nucleus and valence electrons.

Ionization Energy Ionization energy is the energy required to completely remove an electron from a gas atom or an ion. Ionization energy increases going across a period and decreases going down a group.

Electronegativity Electronegativity is a measure of attraction of an atom for the electrons in a chemical bond. Electro negativity increases going across a period and decreases going down a group.

Size Matters for Periodic Trends Ionization Energy and Electronegativity have the same periodic trend. Smaller atoms e- are closer to the nucleus = stronger attraction = harder to pull electrons away from atom Large atoms = valence electrons are further away = electrons are easier to steal

Trends Summarized