Ionic and Covalent Bonding

Valence Electrons

• electrons in the highest occupied energy level

• determines chemical properties

• only electrons are involved in chemical reactions

Chemical Bonding

• The joining of atoms to form new substances

• An intersection that holds two atoms together

• When chemical bonds form, electrons are shared, gained, or lost

Bonding

• valence electrons determine whether an atom can form bonds or not

• Noble gases do NOT form bonds because they have 8 electrons

• Cations have positive charges so metals LOSES electrons

  Anions have negative charges so nonmetals GAINS electrons

Ionic Bonding

• Forms ionic compounds

• Transfers electrons

• One metal (cation) and one nonmetal (anion)

What it looks like

Atoms come near each other

Electrons are transferred from the Metal atom to the Non-metal atom

They stick together because of electrostatic forces, like magnets

Are electrically neutral (no charge)

The total positive charge of the cations equal the negative charge of the anions

Characteristics:

• Hard, brittle solids at room temperature

• Most ionic compounds are salts

• High melting and boiling points

• Ions are held in crystalline

• Conduct electricity when dissolved in H2O

Ionic Compounds

Can be polyatomic or monatomic

Monatomic Ion → ion with only one element Al +3, Na +1

Polyatomic ion → ion with more than one element SO -2, OH -1

Polyatomic Ions

• Definition: A group of atoms together in groups (like a package of atoms) and have a charge like an ion

• Most are negative

• Behave like a singe atom in a compound

• Ammonia (NH+1) is the only positive polyatomic ion

  • behaves like a metal

• Example: Mg + NO3

• Are covalently bonded (electrons are shared)

• Usually combine with other atoms with ionic bonds/transferring electrons

Naming a Polyatomic anion

• Some end in -ate → NO3 nitrate

• Some end in -ite (one oxygen less) → NO2 → nitrite

• With hydrogen use bi → HCO3 bicarbonate

1) Name the cation (unchanged)

2) Name the anion (polyatomic ion)

3) Use parentheses around the whole polyatomic group if more than one is needed, and subscript is outside the ()

Example: Al2 (CO3)3

How to name it

1) Name the cation first (typically a metal) just as it appears on the periodic table

2) Write the anion next (typically a nonmetal and change the ending to -ide

Ex: Sodium + chlorine → Sodium + chloride → Sodium Chloride NaCl

Exceptions for Transition Metals

• They can form ions with different charges

  • Sometimes they lose →2e +2

  • Sometimes they gain→3e- -3

• To indicate their change, use Roman Numerals

• The charge of the transition metal is determined by the anion it bonds with (nonmetal)

• CrP → Chromium (III) Phosphide

  • Phosphorus has -3 so Chromium must have +3

• Silver is always +1

• Zinc is always +2

Covalent Bonding

• Forms molecules

• Sharing electrons

• Between nonmetals or one metalloid and one nonmetal

• ex: H2O

What it looks like

• It’s a chemical bond resulting in the sharing of valence electrons

• Molecule → forms when two or more atoms are covalently bonded

• Since electrons are shared, no charges appear

• Molecules can be different elements like H2O or can be diatomic like O2

• Many combinations can occur between two nonmetals

Characteristics:

• Weaker bonds than ionic

• Low melting point temperature and boiling point temperature

• Nonconductors of electricity in any phase

• Most are liquids and gases

Lewis Structure of Molecules with Multiple Bonds

Single Bond: Covalent bond in which 2 electrons (1 pair) of electrons are shared by 2 atoms

Double Bond: 4 electrons (2 pairs) of e- are shared by 2 atoms

Triple Bond: 6 electrons (3 pairs) are shared by 2 atoms

How to name them

1) First element in the formula is always named first, using the entire name

2) second element in the formula is named using the root of the element and adding the suffix -ide

3) Prefixes are used to indicate the number of atoms of each type that are present in the compound

The prefix mono- is generally omitted for the first element

We eliminate the last letter of a prefix that ends in “o” or “a” when naming an oxide

N2 O5 → dinitrogen pentoxide

Compounds Containing Hydrogen

Acids have a subtsance that produces hydrogen ions (H+) when dissolved in water

To name them:

1) remove the -gen ending from hydrogen

2) change the -ide ending on the second element to -ic

Metallic Bonding

• Occurs between atoms of metals

• electrons are mobile (more freely among all metal atoms)

• Positive ions in a sea of electrons

Metallic Characteristics

• High melting point temperatures, ductile, malleable, shiny

• Hard substances

• Good Conductors of heat and electricity

Names and Formulas of Acids

• When naming an acid, the acid consists of an anion combined with as many hydrogen ions as needed to make the molecule electrically neutral

• H_nX

• X is a monatomic or polyatomic anion

• n is a subscript indicating the number of hydrogen ions that are combined with the anion

• There are 3 rules to name them

Acids with -ide

1) The acid name begins with the prefix hydro-

2) The stem of the anion has the suffix -ic and is followed by the word “acid”

HCI → hydrochloric acid

Acids with -ite

1) The acid name is the stem of the anion

2) with suffix -ous followed by acid

HNO2 → nitrous acid

Acids with -ate

1) stem of the anion with suffix -ic followed by acid

HNO3 → nitric acid