Chapter 19 Chemical Bonds

Section 1 What is Bonding

when atoms combine and form new substances with different Bonding when atoms combine and form new substances with different properties. Example - SALT(clear,edible solid) from: SODIUM(soft,grey metal) CHLORINE(green gas)

Formulas A shorthand way of showing which elements and how much are in a compound. Example - SUGAR: C12H22O11 C,H,O are elements 12,22,11 are subscripts(#of atoms)

Why do atoms bond ? Because their outside level is not full (stable) Can become full by GIVING, TAKING or SHARING e- Example - Dot Diagrams can help see this: . : O: .

Section 2 Types of bonds

Bonding Ionic Metal/nonmetal Give/Take e- Strongest Bond Forms hard crystals, high melting points Charged atoms - called IONS Covalent nonmetal/nonmetal Share e- Weaker bond Forms liquids, and gases, low M.P. Solids Called a MOLECULE Can share 1,2 or 3 pairs of e-

Writing Formulas & Naming Compounds Section 3 Writing Formulas & Naming Compounds

3 simple steps to naming binary ionic (2 part) compounds: Naming Compounds 3 simple steps to naming binary ionic (2 part) compounds: Write the positive ion (metal) Write the negative ion (nonmetal) Drop the ending of the negative and add IDE.

Special Situations Covalent compunds need prefixes: mono, di, tri, tetra, penta 2.Polyatomic ions: use their name(see sheet) 3.Transition Metals: use Roman numerals to show charge

Important Definition: Writing Formulas Important Definition: OXIDATION NUMBER - Number that shows how many e- an atom has gained (-) or lost (+). Example: Al3+ - Aluminium lost 3 e- S2- - Sulfur gained 2 e-

3 simple steps to writing formulas: Write the symbol of the positive oxidation element. Write the symbol of the negative oxidation element or polyatomic ion. Add subscripts to each part so that their sum =0.