Objectives Explain why atoms form bonds Define chemical bond & name three types of chemical bonds

Bonding Atoms Why do atoms bond? - each atom wants a full outermost energy level - gain, lose, and share valence electrons to achieve the duet or octet rule aka: “being happy” - ex. Group 18: He, Ne, Ar

Chemical Bonds Chemical Bonds - attractive force that holds atoms or ions together - 3 types - determines the structure of compound - structure affects properties -

Chemical Structure/Models Chemical Structure/Molecular Models - arrangement of bonded atoms or ions - : the average distance between the nuclei of two bonded atoms - : the angle formed by two bonds to the same atom

Molecular Models of Compounds - atoms are represented by balls - bonds are represented by sticks * good for “seeing” angles - chemical symbols represents atoms - lines are used to represent bonds * good for “seeing” angles H H O

Molecular Models Cont. Space filling - colored circles represent atoms, and the space they take up - no bonds, no bond angles Electron Dot/Lewis Structure - chemical symbol represent atom - dots represent valence electrons - 2 center dots represent a bond - no bond angles, no bond length

Objectives Describe how an ionic, covalent and metallic bonds forms Relate the properties of ionic compounds to the structure of crystal lattices Compare polar and non polar bonds, and demonstrate how polar bonds affect polarity of a molecule Describe the structure and strength of bonds in metals & relate their properties to their structure

Ionic Bonds / Ionic Compounds Definition - bond formed by the attraction between oppositely charged ions cation: anion: - oppositely charged ions attract each other and form an ionic bond ex. Na+ + Cl- = NaCl - electrons are transferred from one atom to another - negative ions attract more positive ions, and soon a network is formed

Networks / Crystal Lattices - ex. NaCl - every Na ion is next to 6 Cl ions - strong attraction between ions creates a rigid framework, or lattice structure: aka: crystals ex, cubes, hexagons, tetragons

Properties of Ionic Compounds Structure affects properties - strong attractions between ions: strong bonds - high melting/boiling pt - shatter when struck (think of it as one unit) - conductivity : ions are so close together, fixed positions, (can’t move) NO conductivity : ions are freely moving due to a broken lattice structure Good conductivity

Covalent Bonds Definition - - can be a single, double, or triple bond single, 2e-’s (-); double, 4e-’s (=); triple, 6e-’s( ) - always formed between nonmetals - mostly low melting/boiling points 2 types of bonds - polar - non polar

Covalent Bond Cont. - bonded atoms that share e-’s equally - same atoms bonded ex. Cl – Cl: Cl2 - bonded atoms that do not share e-’s equally - different atoms bonded H ex. H – N – H: NH3

Metallic Bonds Definition - Properties - Conductivity: Good: electrons can move freely - Malleable: lattice structure is flexible

Predicting Bond Type