Atomic Bonding Lewis Dot Structures Ionic and Covalent Bonding

The Octet Rule Octet Rule- atoms tend to gain, lose or share electrons in order to have a full set of valance electrons. –A full set of valence electrons means… having a full s-orbital AND a full p-orbital. –Ex. Ne- 1s 2 2s 2 2p 6 has a full set of valance electrons. –O- 1s 2 2s 2 2p 4 does not have a full set. ATOMS WITH A FULL SET OF VALANCE ELECTRONS ARE MORE STABLE THAN THOSE THAT DO NOT.

Lewis Dot Structures American Chemist, Gilbert Lewis, developed a way to show only the valence electrons of an atom. This way we can predict if an atom will give up, steal, or share their electrons to fulfill the Octet rule.

Ionic Bonds & Ionic Compounds In an ionic bond, a positively charged ion is attracted to a negatively charged ion. A compound that is composed entirely of ions is called an IONIC COMPOUND.

Ionic Bonds & Ionic Compounds An ionic compound ALWAYS consists of a cation & an anion. Ionic compounds are characterized by: –High melting point –Brittleness –Most are soluble (dissolves easily in H 2 O)

Covalent Bonding A covalent bond SHARES a pair of electrons between 2 atoms. Covalent bonds makes MOLECULES –To describe the composition of the molecule we use a molecular formula. It tells us what elements are in the compound and exactly how many. EX. C 12 H 22 O 11

Covalent Bonding Single covalent bonds- share only one Pair of valence electrons. Multiple covalent bonds- share 2,3 or 4 pairs of covalent bonds. Double bond Triple bond

Covalent Bonding

DOTS or DASHES? Another kind of Lewis structure uses dashes to represent bonds. –1 dash = single bond –2 dashes = double bond –3 dashes = triple bond A non bonding pair of electrons are called a lone pair.

Practice PBr 3 N 2 H 2 CH 3 OH C 3 H 4 NH 3 H 3 PO 4 H 2 SO 4 H 2 CO 3

Naming Chemical Compounds Naming ionic compounds –Positive Ions Monatomic cations (a single atom with a non-negative charge) take the name of the element plus the word "ion" Examples: –Na+ = sodium ion –Zn 2+ = zinc ion Forms more than one (1) positive ion? The charge is indicated by the Roman numeral in parentheses followed by the word "ion" Examples: –Fe 2+ = iron(II) ion –Fe 3+ = iron (III) ion

Negative Ions Monatomic anions (a single atom with a negative charge) change their ending to "-ide" Examples: –O 2- = oxide –Cl - = chloride

When combining cations & anions into an ionic compound, you always put the cation name first & then the anion name (the molecules are also written in that order as well.) Examples: –Na + + Cl - --> NaCl sodium + chloride --> sodium chloride –Cu 2+ + SO >CuSO 4 copper(II) + sulfate --> copper(II) sulfate –Al 3+ + NO 3- --> Al(NO 3 ) 3 aluminum + nitrate --> aluminum nitrate

Practice Compound Name CaI 2 Mg 3 P 2 LiBr Al 2 O 3

Covalent Bonding naming rules The more positive atom is written first (the atom which is the furthest to the left and to the bottom of the periodic table) The more negative second atom has an "- ide" ending. Each prefix indicates the number of each atom present in the compound.

Covalent prefixes Number of Atoms Prefix 1 Mono (not used on 1st element) 2Di 3Tri 4Tetra 5Penta 6Hexa 7Hepta 8Octa 9Nona 10Deca

Practice FormulasName CO 2 CCl 4 P 2 O 5 PBr 3 N 2 O

Practice answers FormulasName CO 2 Carbon Dioxide CCl 4 Carbon Tetrachloride P 2 O 5 Diphosphorous Pentaoxide PBr 3 Phosphorous Tribromide N 2 O Dinitrogen Monoxide

More Practice SO 3 P 3 N 5 N 2 O 5