Molecules and Ions

Particles

Pure Substances

Elements

atoms of the same kind e.g. oxygen

Compounds

atoms of different kinds e.g. water

Mixtures

Homogeneous

e.g solutions,milk

Heterogeneous

e.g. salad,concrete

Can be separated by physical methods

dissolving

evaporating

filtering

sedimentation

distilling

Atoms

Structure of atom

protons

Relative mass is 1.(1.67 x 10^-27 Kg)

Relative charge is +1. (+1.6 x 10^-19 C)

neutrons

Relative mass is 1. (1.67 x 10^-27 Kg)

Relative mass is 0. (0C)

electrons

Relative mass is 1/1830. (9.11 x 10^-31 Kg)

Relative charge is -1. (-1.6 x 10^-19 C)

smallest particle

remain the chemical properties of element

No. of protons = No. of electrons

Mass no. = no.of protons + no.of neutrons

Elements

in their simplest form

cannot be broken down e.g. carbon

Isotopes

Difference in number of neutrons

Atomic Mass

Weighed average of masses of an element

Periodic Table

Atomic number

Symbol of element

Atomic mass

Molecules

covalent bonding

occurs between atoms of non-metals

Ions

Ionic bonding

transfering of electrons from metal to non-metal atom

Ionic compounds

Positive ions(cation)

e.g. sodium ion

Negative ions(anions)

e.g. chloride ion

Combining cation and anion

e.g. sodium chloride, where the overall charge is zero.

Polyatomic ions

e.g. nitrate, carbonate

Covalent compounds

second element ends with "-ide"

e.g. hydrogen chloride

prefix is added to distinguish atoms

Mono- (1)

Di- (2)

Tri- (3)

Tetra- (4)

Penta- (5)

Certain covalent compounds with special names

e.g. water, ammonia, methane

formed when elements are chemically combined together in a chemical reaction.

chemical compounds have constant composition.