BONDING Chapters 4 & 12

Ionic vs. Covalent Bonds result from the attraction between opposite charges of ions Covalent result from sharing of electrons between atoms

The Octet Rule Atoms will gain, lose, or share electrons to achieve a noble gas configuration If the atom has 1-3 valence electrons, it will LOSE those electrons and become a positive ion (CATION). If the atom has 5-7 valence electrons, it will GAIN electrons until it has EIGHT, becoming a negative ion (ANION).

Practice Forming Ions Complete the table below for each of the atoms: # of Valence Electrons GAIN or LOSE electrons? ION CATION or ANION? Magnesium Chlorine Potassium Nitrogen Oxygen Lithium

What are Ionic Compounds? Compound made of only ions Formed by the gaining or losing of electrons Typically between a metal and a non-metal Ionic Bonding A positively charged ion (anion) will be attracted to and will form a bond with a negatively charged ion (cation) The ions will exchange electrons to achieve their charge (and reach the noble gas configuration)

Ionic Attraction?

Properties of Ionic Compounds Overall neutral High melting points Generally brittle solids Dissolve in water to form electrolytes

Types of Ions Monoatomic cations Monoatomic anions Polyatomic ions

Monoatomic cations Positively charged, ions formed from ONE atom To name the cation, simply add the word “ion” after the element’s name Li+ Lithium ion Mg+2 Magnesium ion Some atoms have the ability to form multiple ions (most of these are “transition” metals) To name, simply name the element, indicate the charge in roman numerals and then add the word “ion” Fe+2 Iron (II) ion Fe+3 Iron (III) ion

Monoatomic anion Negatively charged, ions formed from ONE atom To name the anion, replace the ending of the element’s name with “-ide” F - Fluorine  Fluoride O -2 Oxygen  Oxide

Monoatomic ion Practice Complete the table below for each of the atoms: ATOM ION CATION or ANION? NAME of ION Magnesium Chlorine Potassium Nitrogen Oxygen Lithium

Polyatomic ions Multiple atoms that, TOGETHER, carry a charge.

IONIC COMPOUNDS WRITING FORMULAS Write the symbol for the cation first. Write the symbol for the anion second. Add subscripts so the charges equal zero when added. NAMING COMPOUNDS Write the name of the cation unchanged first. Write the root of the anion with the –ide ending.

How do I write a formula for an ionic compound? Use the CRISS-CROSS METHOD: Write the ions in order of metal then nonmetal Take the ionic charge number (written as the superscript) of each element and criss cross it to the subscript of the other element +2 -1 Ca Cl Ca_Cl_ 1 2

Ionic Compound Formula Practice Write the ionic formula for the following ions Mg+2 with P-3 B+3 with S-2 Li+1 with S-2 Ga+3 with Se-2 B+3 with At-1

How do I name ionic compounds? Compounds are named from the ions that form them… The first element (metal) keeps its name If it’s a transition metal, you must use a roman numeral to indicate its charge The second element (nonmetal) keeps the first syllable of its name and the ending is changed to “-ide” NaCl Sodium Chloride Fe2O3 Since Fe is a transition metal, you must find its charge… UNCRISS CROSS Fe2O3 Iron (III) Oxide +3 -2 Fe O

Ionic Compound Naming Practice Write the ionic compound name for the following… BaCl2 NaF Ag2O CuBr CuBr2

Binary Ionic Compounds Binary Compound Ionic compound composed of two atoms Formula Unit Smallest representative unit ATOMS FORMULA NAME of COMPOUND Magnesium & Chlorine IONS: Potassium & Nitrogen Lithium & Oxygen

Tertiary Ionic Compounds Tertiary Compound Ionic compound composed of three atoms IONS FORMULA NAME of COMPOUND K+ and NO3- Mg+2 and OH- Cu+2 and PO4-3

Copper Sulfate Pentahydrate Hydrates PREFIX NUMBER mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10 Ionic compounds that absorb water into their solid structures CuSO4 ● 5H2O Copper Sulfate Pentahydrate

Covalent Compounds Covalent Bond Molecule Molecular Compound Formed by the sharing of electrons Molecule Smallest representative unit Molecular Compound Compounds composed of molecules Molecular Formula Shows the kind and numbers of atoms present in a molecule

Properties of Covalent Compounds made of two nonmetals low melting and boiling points solid, liquid, or gas at room temp. do not dissociate in water

Naming Covalent Compounds Write the less electronegative element first. Write the root of the more electronegative element with the -ide ending second. REVIEW: Electronegativity - the attraction to electrons involved in a chemical bond Add prefixes to both indicating the number of atoms of each element

Exceptions when Naming Covalent Compounds Do not use mono-with the first element in the compound Prefixes are sometimes shortened. CO (Carbon Monoxide) Chemist use common names for some compounds other than the formal names. NH3 (Ammonia)

Naming Covalent Compounds FORMULA NAME of COMPOUND CO CO2 CO3-2 C2O4-2

Types of Covalent Bonds Polar Covalent Bond one atom in a molecule is significantly more electronegative causes a slight positive and negative charge on a molecule. Nonpolar Covalent Bond electrons are shared equally Electronegativity Differences Bond Type  0.4 nonpolar 0.5-1.9 polar  2.0 ionic

Covalent Bonds Single Covalent Bond Double Covalent Bond two atoms share 1 pair of electrons Double Covalent Bond two atoms share 2 pair of electrons Triple Covalent Bond two atoms share 3 pair of electrons

Acid A molecular substance that dissolves in water to produce a hydrogen ion Acts like an ionic compound because they break down into cations and anions in water Produces a characteristic anion for which it is named. If the anion ends with -ide (i.e. chloride or fluoride) Add the prefix hydro- and change the ending to –ic and add the word acid -ate (i.e. phosphate or sulfate) Change the ending to –ic and add the word acid -ite (i.e. sulfite and phosphite) Change the ending to –ous and add the word acid