Section 5-3 Periodic Trends

Atomic Radius Distance from the center of the atom’s nucleus to the outermost electrons. 1. Atoms get larger going down a group. –More energy levels 2. Atoms get smaller moving from left to right. –Atoms have more protons as you move from left to right. –Therefore, the nucleus has a greater pull on the electrons.

Atomic Radius Trend

Ionization Energy The energy needed to remove one of an atom’s electrons. How strong does an atom hold its electrons? 1. Decrease as you move down a group –The smaller the atom the easier it is for the nucleus to hold onto its electrons. –Shielding effect – electrons in lower energy levels shields the outer electrons from the effects of the nucleus

Ionization Energy cont. 2. Increase as you move from left to right across a period. –More valence electrons (closer to fulfilling the octet rule)

Electronegativity The ability to attract to attract electrons in a chemical bond 1. Decrease as you move down a group 2. Usually increase across a period –Exclude noble gases (do not form bond.) –Most electronegative element – Fluorine –Least electronegative element - Francium

Electronegativity Trend

Ionic Size Ions are atoms that have gained or lost electrons –Positive ion – becomes smaller –Negative ion – becomes larger Electron Affinity – the energy change that occurs when it gains an extra electron.