Ionic Radius• Cations are smaller than the atom

they originated from because the same number of protons in the nucleus pulls on less electrons• Anions are larger than the atom they

originated from because the same number of protons in the nucleus pulls on more electrons

• Radius of ions increases down a group and decreases across a period•Metals usually become cations• Nonmetals usually form anions

Electronegativity• Electronegativity (EN) is the attraction of an

atom in a compound for an electron• The scale was developed by Linus Pauling.

• F= 4.0 Cs=0.7 • EN can be used to determine the type of bond

that will form between two atoms. • EN decreases down a group and increases

across a period. Group 18 is an exception.