Periodic Table: Valence Electrons, Ion Charges, and Trends in Chemistry

Valence Electrons

Group 1 = 1VE, Group 2 = 2VEs, Group 13 = 3VEs, Group 14 = 4VEs, Group 18 = 8VEs

Monatomic Ion Charges

Group 1 = +1, Group 2 = +2, Group 13 = +3, Group 15 = -3, Group 16 = -2, Group 17 = -1

Types of Compounds

Ionic and Covalent Compounds

Characteristics of Ionic Compounds

Transfer of electrons, Metals(+/Cations) and Nonmetals(-/Anion), Metal (or NH+4)+ Polyatomic Ion (charged molecule)

Characteristics of Covalent Compounds

Sharing electrons, nonmetal + nonmetal, no charges

Rules for Forming Ionic Compounds

The ionic compound must be neutral overall, and the total positives must equal the total number of negatives

Tips for Writing Ionic Compounds

NH+4 makes an ionic compound, metal is written before anion, the total charge is 0, parenthesis is needed for more than one polyatomic ion, do not change the subscription on the polyatomic ion

Periodic Trends

Atomic Radius, Ionization Energy, and Electronegativity

Atomic Radius

The distance from the center of the nucleus to outermost electrons

Direction Atomic Radius Increases

To the left and down

Ionization Energy

The energy required to remove the outermost electron from atoms (forming a +1 ion)

Direction Ionization Energy Increases

To the right and up

Electronegativity

An atom's ability to attract electrons within a bond

Direction Electronegativity Increases

To the right and up

Reason for Decrease in Ionization Energy Down a Group

Outer electrons are farther from the nucleus as we add occupied energy levels and electrons are held less tightly

Reason for Increase in Ionization Energy Left to Right

More protons are added to the nucleus and electrons are held more tightly

Reason for Increase in Atomic Radius Down a Group

Occupied orbits are added as you go down so the atoms get bigger

Reason for Decrease in Atomic Radius Left to Right

More protons are added to the nucleus so the protons pull electrons/energy levels in