Chemical Stability

All elements want chemical stability. This can happen by: 1. Forming Ions 2. Forming chemical bonds (making compounds)

Ion An atom (or group of atoms) that has lost or gained e- and has a net electric charge. – Cation (+) – Anion (-) Atom vs. Ion What is an Ion?

Valence Electrons The number of electrons in the outer orbital of an atom.

Ionization Atoms become ions in order to have a complete energy level. Fluorine Atom Fluorine Ion

Ionization Oxygen atoms have 6 valence electrons Oxygen ions gain 2 e- and becomes O –2

Ionization Magnesium atoms have 2 valence electrons Magnesium ions lose 2 e- and become Mg +2

Oxidation Number The ion “charge”.

Oxidation Numbers Oxygen ion: O –2 [gained two e-] Magnesium ion: Mg +2 [lost two e-]

Electron Dot Diagrams Diagrams that display only the valence electrons

Electron Dot Diagrams AtomIon Mgloses 2e-Mg +2 Ngains 3e- N -3 Liloses 1e- Li +1

Polyatomic Ions A group of atoms with a net charge. OH -1 NO 3 -1 PO CO 3 -2

Polyatomic Ions How to Remember Certain Common Polyatomic Ions Nick the Camel ate a Clam for Supper in Phoenix

Compounds Two or more elements chemically bonded to form a new substance (with different properties).

Compounds Shown by: – Chemical Formula H 2 O – Structural Formula O H

Compounds Chemical Formula Coefficient 3H 2 O (# of Molecules) Subscript (# of atoms) Parentheses (OH) 2 = chemical groups

Compounds Counting Atoms in Chemical Formulas 3H 2 O

Compounds Counting Atoms in Chemical Formulas 6CO 2 4NaHCO 3 3H 3 PO 4 5Mg(OH) 2 2Fe 3 Al 2 (SiO 4 ) 3

Chemical Bonding Chemical Bonding occurs to achieve Chemical Stability.Chemical Bonding occurs to achieve Chemical Stability. Atoms gain, lose or share valence electrons.Atoms gain, lose or share valence electrons. Why do Atoms Bond? Bonding Song

Types of Bonds Ionic Covalent Metallic

The Type of Bonding Depends on the Difference in the Electronegativity of the Atoms. Ionic Non-Polar CovalentPolar Covalent

Ionic Bonds Bonds formed by the attraction between oppositely charged ions. [e- are given away or received] Ionic Bonding

Ionic Bonding Rules: 1)Metals form ionic bonds with non- metals. 2)Metal form ionic bonds with polyatomic ions. 3)Polyatomic ions form ionic bonds with each other.

Ionic Bonding Lewis Dot Diagrams show chemical bonds resulting from interaction of valence e- and the ion charges. _

Predicting Chemical Formulas with Oxidation #s Mg +2 + Cl -  MgCl 2 Ca +2 + NO 3 -  Ca(NO 3 ) 2 Writing Formulas for Binary Compounds Polyatomic Compounds

Naming Ionic Compounds Names are additions of cations and anions Cation (1 st ) is usually the name of the element. Anion (next) is the 1 st syllable of the element PLUS the suffix “ide”

Examples: Li and F = Lithium Fluoride Mn and O = Manganese Oxide

Ionic Compounds with Polyatomic Ions Name the Cation, then the Polyatomic Ion. Ca +2 + (CO 3 -2 ) ions = Calcium Carbonate Na + + (CN - ) ions = Sodium Cyanide Ba +2 + (SO 3 -2 ) ions = Barium Sulfite

Covalent Bonds Bonds formed by sharing electrons. Ionic vs. Covalent Bonding Covalent Bonding

Covalent Bonding Rules: 1)Hydrogen forms covalent bonds with metals, non-metals and polyatomic ions. 2)Nonmetals form covalent bonds with other nonmetals.

Covalent Bonds in EDD

Diatomic Molecules Some atoms, (mainly gases) share their extra electrons.

Polar and Non-Polar Covalent Molecules If the electronegativity of the atoms are about the same, they share equally and form a Non-Polar compound. If the electronegativity of one type of atom is greater than the other, the electrons are not shared equally and a Polar compound is formed.

Polar and Non-Polar Covalent Molecules

Naming Covalent Compounds Covalent Compounds are molecules (not ions) bonded together. Name reflects the numbers of each element in the compound. Use Latin prefixes.

Latin Prefixes One (1): Mono Two (2): Di Three (3): Tri Four (4): Tetra or Tetr Five (5): Pent or Penta Six (6): Hex or Hexa Seven (7): Hept or Hepta

Examples P 2 O 5 Di = 2, Pent = 5 Diphosphorous Pentoxide SiO 2 Di = 2Silicon Dioxide

There’s always an Exception If the first letter of the atom is a vowel, drop the “a”. Examples: – Dinitrogen Tetroxide – Carbon Tetrafluoride

Ionic vs. Covalent Molecules Ionic compounds form a network of ions. Covalent compounds form individual molecules.

Ionic vs. Covalent Molecules Properties of Ionic Compounds High Melting / Boiling Points Brittle Many are Water Soluble When dissolved in water, conduct electricity because they are charged particles [Electrolytes]. Properties of Ionic Compounds How water Dissolves Salt

Ionic vs. Covalent Molecules Properties of Covalent Compounds Low Melting / Boiling Points Usually Liquid or Gas “Like Dissolves Like” Since they are neutral molecules, they do not conduct electricity when dissolved in water. Properties of Covalent Molecules Like Dissolves Like