- 1 - CHEMISTRY 2 REVIEW: MIDTERM Everything Energy Matter ...

Bonding: Ionic vs. Molecular
• Valence electrons are the electrons in the highest occupied energy level of an atom.
• The number of valence electrons for a representative element is equal to the last number of its group
number. Example: phosphorus is in group 15 – it has 5 valence electrons.
• The octet rule: atoms tend to gain, lose or share electrons in order to have the electron configuration of
•
a noble gas
Chemical Names and Formulas
§ Ionic Compounds
o Commonly a metal + nonmetal
o Cation + anion
o Combine in a ratio so that the net charge is zero
o Use criss-cross method to write formula
§ Naming an ionic compound from a formula
o Name of cation + name of anion
o Example Al2O3 = aluminum oxide
§ Molecular Compounds
o Commonly two non-metals
o Name from formula for binary compound
§ Element 1: Prefix (if subscript > 1) +
name of element
§ Element 2: prefix + stem of name + -ide
§ Example: N2O5 = dinitrogen pentoxide
1 Mono 6 Hexa
2 Di 7 Hepta
3 Tri 8 Octa
4 Tetra 9 Nona
5 Penta 10 Deca
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CATIONS ANIONS
Form from metals Form from non-metals
Lose electrons Gain electrons
Positively charged Negatively charged
Charge = #electrons
lost
Type of
elements
IONIC
Charge = # electrons
lost
COMPOUNDS
MOLECULAR
COMPOUNDS
Metal + non-metal Non-metals only
Type of bond Ionic bond Covalent bond
Origin of
bonding
Smallest
particles
Transfer of
electrons
Sharing of
electrons
Ions Molecules