Chemical Formulas and Chemical Bonding Obj: Identify how many of each element are in a compound based on the chemical formula. Explain why and how elements bonds Chemical Formulas and Chemical Bonding

Chemical Formulas Shows: How many elements are in a compound Ratio of atoms in a compound

Chemical Bonds Strong attractive force b/t atoms or ions in a molecule or cmpd. Formed by: Transferring e- (losing or gaining) Sharing e-

Stability Octet Rule: Most form bonds to have 8 valence e- Full outer energy level Stability is the driving force behind bond formation

What Determines Bonding? Elements bond based on the amount of e- they have and the charge they have.

Ionic Bonds Formed b/t two ions by the transfer of electrons Metal interact with nonmetals Positive ions form when the number of e- are less than the number of protons Group 1 metals  ion 1+ Group 2 metals  ion 2+ Group 13 metals  ion 3+

Transferring e-

Check for Understanding 1. Number of valence e- in Aluminum A. 1 e- B. 2 e- C. 3 e- 2. Change in e- for octet A. lose 3 e- B. gain 3 e- C. gain 5 e- 3. Ionic charge of Al A. 3- B. 5- C. 3+

Check for Understanding Give the ionic charge for each of the following: 12 p+ and 10 e- O 2+ 2- 50 p+ and 46 e- 2+ 4+ 4- 15 p+ and 18 e- 3+ 3- 5-

Nonmetal ions Nonmetals in 15, 16 and 17 gain e- from metals Nonmetals add e- to achieve octet arrangement Nonmetal ionic charge: -3, -2, or -1

Ionic Bonds

Ionic Bonds Ionic bond—e- from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charge particles or ions

Covalent Bonds Formed by the sharing of e-

Covalent Bonds Between nonmetallic elements of similar electronegativity. Formed by sharing e- pairs Stable non-ionizing particles Bonds in all polyatomic and diatomic are all covalent bonds

Polar vs. Nonpolar Nonpolar covalent bonds—when e- are shared equally

Polar Covalent Bonds Formed when e- are shared but shared unequally

Water is a polar molecule because oxygen is more electronegative than hydrogen, and e- are pulled closer to oxygen

Metallic Bonds Bond found in metals Holds metal atoms together very strongly Formed b/t atoms of metallic elements Form alloys: They do not combine with other metals Alloy—solution of a metal in a metal (steel, brass, bronze and pewter)

Formula Weights Sum of atomic masses

Check for Understanding Compute the mass of the following cmpds. Round to the nearest tenth and state the type of bond NaCl C2H6 Na (CO3)2