The Making of Compounds

Compounds

Compounds – The combination of two or more elements.

Have new chemical and physical properties…different from each element.

Most of the matter around us is in the form of compounds or mixtures of compounds.

Compounds

Ex: Sodium – shiny, soft, gray metal…reacts violently with water

Ex: Chlorine – greenish, yellow gas … can kill if in air.

The compound of Sodium and Chlorine make SALT.

Compounds

Made through CHEMICAL BONDS – attractive force that holds atoms together.

Chemical Formula – The chemical shorthand for a compound.– Includes the chemical symbols and the

number of atoms of that element.

Compounds The goal of every atom is to be

chemically stable…with 8 outer electrons. (Octet Rule)

An atom will form compounds to become stable.

An atom only uses its valence electrons to form compounds.

Can use Dot Diagrams to show the number of electrons in the outer shell.

Dot Diagrams and Compounds Ex: Water (H2O)

Hydrogen has one valence electron Oxygen has 6 valence electrons Neither are stable…Will form a

compound to become stable

Types of Chemical Bonds: Ionic Bonding Ionic Bonds –

The force of attraction between opposite charges of ions– Simple

definition: Atoms give up or take electrons to become stable.

Ionic Bonding Example Sodium has one valence

electron Chlorine has 7 valence

electrons Sodium gives up its 1

electron to Chlorine…They both become STABLE

Sodium becomes positive (gives up electron

Chlorine becomes negative (takes an electron)

Types of Chemical Bonds: Covalent Bonding Covalent Bond – A bond that forms

between atoms when they SHARE electrons

Covalent Bonds (example) CH4 is made with Carbon

and Hydrogen sharing electrons.

Carbon has 4 valence electrons

Hydrogen has 1 valence electron

Carbon bonds with 4 Hydrogen atoms to become stable…they SHARE electrons to make all parties happy

Oxidation Numbers

The number of electrons that an atom will give up or take.

Useful when making compounds. Oxidation numbers are known by the group

an element is in– Example Group 1 – Oxidation # +1– Group 2 - +2– (handout shows oxidation numbers)

Groups 3-12 have variable oxidation numbers…depends on the compound it is making.

Polyatomic Ions

An ion made of two or more atoms. These are groups of covalently bonded

atoms that have either lost or gained electrons. (combination of bonds)

Polyatomic Ions are often found together in nature…have own name and oxidation numbers.

Polyatomic Ions(p. 158)

Put the following on your periodic chart:

Ammonium

Carbonate

Chlorate

Hydroxide

Nitrate

Phosphate

Sulfate

Making Compounds…Names and Formulas Compound Formulas – made with the

chemical symbol and the number of atoms used

Example: H2O uses 2 Hydrogen atoms for every 1 Oxygen atom.

Example: H2SO4 uses 2 Hydrogen atoms to 1 Sulfate ion

Making Compounds

1. Find Chemical Symbols 2. Find Oxidation Number for that

Element 3. Write the Chemical Symbol with the

Oxidation Number as a Superscript– Example: Sodium and Chlorine– Na+1 Cl-1

Making Compounds 4. Criss-cross the oxidation numbers…(give

the number to the opposite element as a subscript)– Na+1 Cl-1

– To: Na-1 Cl+1

5. Drop the sign (+ / -)– Na1Cl1

6. Write the compound – NaCl (when the subscript is 1 it does not have

to be written)

Making CompoundsPractice Practice:

– 1. Calcium and Nitrogen– 2. Magnesium and Oxygen– 3. Calcium and Chlorine

Making CompoundsPractice Answers: 1. Calcium and Nitrogen

– Ca+2 Nitrogen-3

– Ca3N2

2. Magnesium and Oxygen– Mg+2 O-2

– Mg2O2 or MgO

3. Calcium and Chlorine– Ca+2 Cl-1

– CaCl2

Naming Compounds

Most of the time you can name an IONIC Compound by– 1. Writing the Name of the FIRST

ELEMENT– 2. Writing the ROOT of the SECOND

ELEMENT– 3. Adding –IDE to the root

Naming Compounds: Examples

CaCl2 - Calcium chloride

K3P - Potassium phosphide

Al2S3- Aluminum sulfide

Naming Compounds

Some of our metals have more than one ionic charge– 1. We have to figure out what the ionic

charge is– 2. Then we must show which of the

elements it is with a roman numeral

Naming Compounds: Examples

FeCl2 - Iron(II) chloride

FeCl3 - Iron(III) chloride

PbBr2 - Lead(II) bromide

Naming Compounds

If the compound has a polyatomic ion in it:– 1. Write the name of the FIRST element– 2. Then find the name of the

POLYATOMIC ION and write it

Naming Compounds:With Polyatomic Ions

Fe(OH)2 - Iron(II) hydroxide

Ca3(PO4)2 - Calcium phosphate

Na2SO4 - Sodium sulfate