Chemical Bonds Chapter 20

Sec. 1 - Combined Elements Elements make  compounds Properties of compounds are different from elements Ex: Sodium Chloride, NaCl (table salt) –Na: silver, metal, reacts violently w/ H 2 O –Cl: poisonous greenish-yellow gas

Chemical Formulas H 2 O  2 atoms H and 1 atom O

Atomic Stability Why do atoms form compounds? To be stable Why don’t noble gases form compounds? Stable!  Full energy levels!! All atoms form compounds to get FULL ENERGY LEVELS  stable

Atomic Stability

1 st energy level full with 2 e - Other levels full with 8 e -

Stability is Reached NaCl is made from atoms losing or gaining electrons H 2 O is different  elements share electrons Both ways make a… Chemical Bond: force that holds atoms together in a compound

Types of Bonds Section 2

Ionic Bonds Atoms can lose or gain e - to make an ion Ion: a charged particle because it now has either more or fewer e - than p + + charge: if fewer e - than p + - charge: if more e - than p +

Calcium Oxide - CaO Calcium has 2 valence e - Loses 2 e - and becomes an ion Ca +2 Oxygen has 6 valence e - Gains 2 e - and becomes an ion O -2 Calcium gives e - to Oxygen Opposite charges ATTRACT!!

Ionic Bond – Metal and Nonmetal Def: the force of attraction between opposite charges of the ions Ex: MgCl 2 – zero net charge Smallest Particle = formula unit

Covalent Bond – 2 Nonmetals Def: attraction between atoms when they share electrons Smallest particle = molecule H 2 O CO 2 N 2

Covalent Bonds Single Covalent Bond: 2 shared electrons Multiple Bonds: –Double (4 shared e - ) –Triple (6 shared e - )

Naming Compounds Section 3

Naming Ionic Compounds Binary compound: has 2 elements Ionic compounds – name of ions makes name of compound Positive Ions: name of element –Na + = Sodium ion Negative ions end in – ide –Cl - = Chloride ion

Special Ions

Polyatomic Ions

Sec. 3 – Writing Formulas Remember… compounds are NEUTRAL!! 1.Write the (+) ion 2.Write the (-) ion 3.Balance charges: criss-cross method Reduce to smallest whole #s

Write the Formula Lithium Nitride Lead(IV) Phosphide Calcium Fluoride Ammonium Phosphate Magnesium Hydroxide

Naming Ionic Compounds Put the two ion names together! NaCl –Na + = Sodium ion –Cl - = Chloride ion – Sodium Chloride

Practice Naming RbCl Mg 3 N 2 AlF 3 CrCl 3 Ca(OH) 2 Na 2 CO 3 NH 4 Cl

Naming Covalent Compounds No ions involved Same elements can make different compounds: CO, CO 2 Naming: Use prefixes to tell how many atoms of each element Second element ends in -ide Prefix mono is left out with the first element

Prefixes

Practice Naming N 4 O 6 C 2 O 5 PH 3 Sulfur Hexafluoride Dihydrogen Monoxide

Hydrates Def: has water chemically attached to its ions CoCl 2 6H 2 O Cobalt Chloride Hexahydrate CaSO 4 2H 2 O Calcium Sulfate Dihydrate