Chemical Bonds  Atoms bond to become stable “happy” – octet rule  When atoms bond they form neutral compounds.  A binary compound is made of 2 elements  Each binary compound has its own chemical formula  A binary chemical formula consists of 2 element symbols and may have subscripts.

CHEMICAL FORMULAS  The subscript is a number at the bottom of a chemical formula.  The subscript represents how many atoms of each element are required to make a neutral compound MgCl 2 There is 1- Mg & 2 – Cl Never use 1 as a subscript!

IONIC BOND bond formed between a metal and nonmetal ions that transfer of electrons

Formation of Ions Ionic compounds result when metals bond with nonmetals Metals lose electrons to form a positive charge Nonmetals gain electrons to form a negative charge Metals: Nonmetals: Na + N -3 Ca +2 S -2 Al +3 Br -

IONIC BONDS  Form between the (+) & (-) charged ions.  Form a “network” of ions – very strong bonds.  Conducts electricity when melted or dissolved in water.

Writing Binary Ionic Formulas Calcium & oxygen  Write the metal ion Ca +2  Write the nonmetal ion O -2 If charges cancel – ratio is 1:1 ( 1 of each) CaO Magnesium & chlorine  Write the metal ion Mg +2  Write the nonmetal ion Cl - If charges DO NOT cancel – drop & swap MgCl 2

Practice  Magnesium & iodine  Strontium & bromine  Barium & nitrogen  Aluminum & phosphorus

Naming Binary Ionic Formula  Representative Metals Name the metal Change the ending of the nonmetal to – ide Cl – chloride C - carbide F – flouride Se - selenide I – iodide N – nitride P – phosphide S – sulfide Br – bromide O – oxide MgCl 2 - magnesium chloride AlP - aluminum phosphide

Practice  CaBr 2  Na 3 N  BCl 3  MgO  AlCl 3  Na 3 N  SrO K2SK2S

Practice - Work with a partner or by yourself!!! 1. Pick up the following from the front table: Deck of element cards (1 per group if working with a partner) Roll the Dice worksheet 2. Using the deck of element cards, make a stack of metals and nonmetals & then turn each stack face down. (you can use your colored PT for help ) 3. Flip over 1 metal (cation) and 1 nonmetal (anion) to fill in the Roll the Dice worksheet – be sure to write the ION charge. (you can use your colored PT for help) 4.Use the cation and anion charges to write the neutral chemical formula

COVALENT BOND bond formed by the sharing of electrons

Covalent Compounds Covalent compounds result when nonmetals react with nonmetals Both nonmetals share their valence electrons to be happy – Octet Rule Examples: CO 2 SCl 2 H 2 OCH 4

Covalent formulas Use prefixes to show the # of atoms of each element in a covalent compound  1 – mono 6 - hexa  2 – di 7 - hepta  3 – tri 8- octa  4 – tetra9 - nona  5 – penta10 – deca YOU MUST MEMORIZE THESE!!!!

Naming Covalent Compounds  1 st element – use prefixes only of the # of atoms is greater than 1  2 nd element – use prefixes; change ending to – ide  CO 2 Carbon Dioxide  N 3 Cl 7 Trinitrogen Heptachloride

Practice  CO 2  N 3 F 8  Se 4 Br 9  S 7 O tetraselenium nonabromide trinitrogen octaflouride heptasulfur monoxide carbon dioxide

Writing Covalent formulas  Use the prefix to identify how many of each nonmetal atoms are in each molecule.  The prefix is written before the element name.  The prefix becomes the subscript. Carbon TetrahydrideDisulfur Hexachloride ○ CH 4 S 2 Cl 6

1)Name the following covalent compounds: a)SiF 4 b)N 2 S 3 c)H 3 Br 7 d)S 5 Br 9 e) H 2 O 2)Write the formulas for the following covalent compounds: a)diboron hexahydride b)nitrogen tribromide c)sulfur hexachloride d)diphosphorus pentoxide