Molecules and Ions

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Molecules and Ions

Forming Compounds

chemical compounds have constant composition.

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

Covalent compounds

Certain covalent compounds with special names

e.g. water, ammonia, methane

prefix is added to distinguish atoms

Penta- (5)

Tetra- (4)

Tri- (3)

Di- (2)

Mono- (1)

second element ends with "-ide"

e.g. hydrogen chloride

Ionic compounds

Polyatomic ions

e.g. nitrate, carbonate

Combining cation and anion

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

Negative ions(anions)

e.g. chloride ion

Positive ions(cation)

e.g. sodium ion

Ions

Ionic bonding

transfering of electrons from metal to non-metal atom

Molecules

covalent bonding

occurs between atoms of non-metals

Basic Constituent of matter

Periodic Table

Atomic mass

Symbol of element

Atomic number

Atomic Mass

Weighed average of masses of an element

Isotopes

Difference in number of neutrons

cannot be broken down e.g. carbon

in their simplest form

Atoms

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

No. of protons = No. of electrons

remain the chemical properties of element

smallest particle

Structure of atom

electrons

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

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

neutrons

Relative mass is 0. (0C)

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

protons

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

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

Classification of matter

Particles

Can be separated by physical methods

distilling

sedimentation

filtering

evaporating

dissolving

Mixtures

Heterogeneous

e.g. salad,concrete

Homogeneous

e.g solutions,milk

Pure Substances

Compounds

atoms of different kinds e.g. water

Elements

atoms of the same kind e.g. oxygen