Bonding and Nomentclature UNit

Unit Learning Goal Attraction and repulsion between ele

ctric charges at the atomic scale explain the structure, properties, and transformations of matter, as well as the classification of the matter.

Bonding-1

Valence Electrons and the Octet Rule

Valence Electrons and Bonding

Valence Electrons and Bonding

Valence Electrons What are they?▪ Outer Shell Electrons

These electrons make all bonds happen.

Octet Rule

All atoms “want” to obtain the electron configuration of a noble gas

Usually this is 8 outer shell electrons

Lewis Dot

Dots to indicate the number of electrons in the outer shell

Na Ca O

N F Si

12 3 4 5 6 7

8NUMBER OF VALENCE ELECTRONS

Octet Rule: How Achieved

Achieve Noble Gas Give & Take of

Electrons▪ =Ionic Bond

Sharing Electrons▪ =Covalent Bond

Bonding-2Ionic Bonding

Ionic Bonds

Ionic bonds occur because of a Transfer of Electrons

These two atoms are NOT happy: How can we help them out?

The atom with the extra electrons gives them to the one who “wants” electrons

+2 -2

Note that after the transfer of electrons the atoms acquire a charge: +2 and -2

oxidation number

The oxidation number of an element indicates the number of electrons lost, gained, or shared as a result of chemical bonding. It is the charge of atoms after they have their complete octet.

What Causes the Ions to be attracted?

Ions are always attracted to each other due to the attraction between opposite electrical charges.

Positive and negative charged ions attract each other till the total charge is ZERO.

1 Na+ + 1 Cl- = NaCl no charge (balanced)

Ionic Bonds

Definitions Salt

Ionic compounds are often referred to as salts. Crystal Lattice▪ A repetitive arrangement of atoms in an ionic

compound

A large Salt Crystal

Crystal Lattice

One Na for every one Cl

Crystal Lattice Explained

Formula is a ratio: NaCl does not mean one Na connected to one Cl

It means Na1,000,000Cl1,000,000

So it looks like…

Ionic Bonds

Property Reason

High melting point Due to strong bonds

Do not conduct electricity when solid

Electrons can’t move

Solids at room temp. Strong bonds

Good conductors when dissolved or liquid

Ions are free to move

Brittle and hard Strong bonds

Compound with Polyatomic ions Polyatomic Ions are ions that have more

than one atom. Often these ions can include nonmetal atoms.

Polyatomic ions are groups of atoms that act together as one unit

Transition Metals

Transition Metals are always cations just like all metals.

Transition Metals often have more than one possible charge. It is necessary to check for possible charges when we make our ionic compounds.

Common Transition elements with more than one ion formation

Ionic Bonding Lewis Dot Example

Polyatomic Ions

We must consider these ions as groups that always travel together.

Iron Oxides

Iron II Oxide ` Iron III Oxide

Nomenclature

THE NAME OF COMPOUNDS ARE VERY IMPORTANT!

Because they tell you what is in that compound!

How do I know the ion formed by various elements?

The periodic table group numbers signify the number of valence electrons members of that group each have.

The valence electron number will indicate whether or not that element/group will lose or gain electrons, and how many Groups 1-3 and the transition elements lose

electrons to become positive ions Groups 5-7 gain electrons to become negative ions Group 4 and 8 do not readily form ions

The periodic table as a useful tool

Naming Basics: Ionic Compounds

Ionic compounds are formed between a metal and a nonmetal Metals: groups 1, 2, 3, & the transition

metals (short rows) Nonmetals: primarily groups 5, 6, & 7

To name them: Cation + (Anion + ide) Cation: positive ion Anion: negative ion Na + Cl = Sodium Chloride

Determining the molecular formula of an ionic compound

Compounds are by definition neutral. When combining ions to form an ionic compound, the overall charge of the compound must equal zero

Subscripts are used to indicate the number of each element needed in order to have a neutral compound

For example: Na + Cl = NaCl (+1, -1 equals zero) Mg + Br = MgBr2 (+2, -1, -1 equals zero)

Compounds with Polyatomic ions

When naming compounds with polyatomic ions, use the name of the polyatomic ion with no –ide suffix

For example: K2S = Potassium sulfide while K3PO4 = Potassium phosphate

In the example above, the rules for determining subscripts remains the same: the goal is for the compound to be neutral (no electrical charge)

K = +1 charge, PO4 = -3 charge and so I will need three K+ ions to bond with one PO4 polyatomic ion in order to reach an electrical charge of zero (neutral

Compounds with elements that form more than one type of Ion (multiple charges)

When naming a compound containing an element that can form more than one type of ion, a Roman numeral is used to indicate the charge of that ion in that particular compound

Copper (II) Oxide: Copper has a +2 charge, and therefore the formula will be CuO

Copper (I) Oxide: Copper has a +1 charge and therefore the formula will be Cu2O

Common Transition elements with more than one ion formation

Naming compounds containing only nonmetals

When nonmetals combine, the naming system is different. Because you cannot necessarily use the charge to

indicate the quantities of each atom in the compound, the name must indicate the amounts using standard prefixes: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, and deca

The only time a prefix is not used is for the first element of the name when there is only one of that element in the compound. CO carbon monoxide N2O4 dinitrogen tetraoxide