Chemistry Unit 2(2013-2014)

• What is an ion?• Define ionic bond.• Define covalent bond.• Define valence electrons• Define Chemical Compound• Define binary compound (ionic or molecular)• Define ternary compound

Compound

• Are formed when two or more atoms join together• All molecules of a chemical compound have the

same types and number of atoms

• Why do atoms combine?– To become stable (to fill outer electron shell)

• How do atoms combine?– By gaining or losing electrons– By sharing electrons– By metallic bonding

Types of Compounds• Binary ionic compound : two different elements, one is metal

the other is nonmetal.KCl, NaCl,

• Binary molecular compound: two elements both are nonmetals Ex. H2O or NH3,

H2 is a molecular compound but it is not a binary molecular compound

• Ternary ionic compound: three different elements, one is metal the others are nonmetals.KNO3 , Al(NO3)3 , C6H12O6

CHEMICAL BONDSPage 602-614

A) IONIC BONDS: - chemical bond between metal & non-metal

- electrons transfer takes place

B) COVALENT BONDS:- chemical bond between two non-metals- electron sharing takes place

C) METALLIC BONDS- chemical bond between two metals- positive charged metal ions are surrounded by cloud

of electrons. This is why metals are conductors. Pg.571

Intramolecular bonds a) Ionic bonding: transfer of electron. It occurs between metal and non metal. Metal gives electron, non-metal takes electron. Why?

Ionic bond

Intramolecular bonds b) Covalent bonding

Atoms share the electron pairs.

It occurs between two non-metals

Formation of covalent bond

METALLIC BOND

METALLIC BOND

• Monoatomic ion: It has only one atom• Ex. Na1+ Cl1-

• Polyatomic ion: it has more than one atom• Ex. NH4

+ CO32-

Monoatomic ions

Monoatomic and polyatomic positive ions

Monoatomic and polyatomic negative ions

Oxidation number

• An oxidation number tells us how many electrons an atom has gained, lost or shared to become stable.

For ionic compound the oxidation number is the same as the charge on the ion.

• Ex. Na has 1+ its oxidation number is 1+

• Cl has 1- so its oxidation number is 1-

What is the oxidation number of Fe in the compound Fe2S3 ?

What is the oxidation number of Cu in the compound CuO ?

Writing Formulas

1- Write the symbol of the element or polyatomic ion that has

the positive charge. (Hydrogen, ammonium, NH+ and all metals have positive charge)

2- Write the symbol of the element or polyatomic ion that has the negative charge. (Nonmetals other than hydrogen and polyatomic ions other than NH4

+ Have negative charge)

3- The charge (without the sign) of one ion becomes the subscript of the other ion.

What is the chemical formula for lead (II) oxide?

What is the name of KOH?

• What is the formula for lithium nitride• Li1+ N3-

• Li1+ + N3- Li3N1

or Li3N

• What is the formula for calcium chloride?

Writing names(ionic compounds)

1- Write the names of the positive ion.2- Using the Table 2, check to see if the positive ion is capable of

forming more than one oxidation number. If it is, determine the oxidation number of the ion from the formula of the compound. Overall charge is zero and the negative ion has only one possible charge. Write the the charge of the positive ion using roman numerals in parentheses after the ion’s name.

3- Write the root name of the negative ion. The root name is the first part of the element’s name. Ex. Chlorine chlor-, oxygen ox-

4- Add the ending –ide to the root. Ex. BaF2 is named barium fluoride

• Write the name of the first element. If its subscript is more than one add appropriate Greek prefix to the name.

• Write the root name of the second element with the –ide ending. If its subscript is more than one add appropriate Greek prefix to the name.

• Ex. NO, NO2, N2O, N2O5

Writing names(molecular compounds)

Chemical equations

• Why do scientists use chemical equations?

It is easier to write/shorter than the wordsIt gives the states (gas, liquid, solid) of the

matter

What are the reactants? What are the products?C6H12O6 + 6O2 ---------- 6CO2 + 6H2O

• What information does this chemical equation give you?

Zn(s) + 2HCl(aq) H2 (g) + ZnCl2

(aq)

States of matter for each substances involved.How much of each atom and each substances

What is the law of conservation mass?

• The mass of the reactants must equal the mass of the products, mass is not created or destroyed.

Zn(s) + 2HCl(aq) H2 (g) + ZnCl2

(aq)

In the equation above, how much H2 gas was produced if 22 g of

Zn reacts with 15 g of HCl and 28 g of ZnCl2 remains?

Zn(s) + 2HCl(aq) H2 (g) + ZnCl2

(aq)

22 g 15 g

? g 28

g

Reactants: 22+15=37Products: 22+?=37?= 37-28= 9 g

Coefficient and Subscripts

• Coefficients represent the number of units of each substance taking part in a reaction. 4NO2 coefficient number of NO2 is 4, means there are 4 NO2 molecule.

• Subscript: is a digit in a chemical formula that represents the number of atoms or ions occurring in the substance.

Ex: NO2 subscript of oxygen is 2, means there are two oxygen atom in the compound.

Balancing a Reaction

1- Write a chemical equation for the reaction2- Count the atoms in the reactants and the

products.3- Chose coefficients that will bring the equation

closer to balanced.4- Recheck the numbers of each atom on each

side of the equation.5- Repeat steps 3 and 4 until the equation is

balanced.

Balancing a Reaction• HgO(s) Hg (l) + O2

Atoms HgO(s) Hg (l) + O2

Hg 1 1O 1 2Which coefficient can we use to balance it?Can we change subscripts? NO

Atoms 2HgO(s) 2Hg (l) + O2

Balance the following equations.

1- Mg(s) + O2 MgO

2- Li(s) + H2O LiOH + H2

Why do the equations need to be balanced?

• Because of the law of conservation of mass which states that;

the mass of the reactants must be = the mass of the product