Chemistry Notes. Standard Grade.

MASS & CHARGE

• Proton- positive, mass 1
• electron- negative, mass 0
• neutron- neutral, mass 1

working out..

• protons - equal ro atomic number
• neutrons - mass number minus atomic number (protons)
• electrons - equal to the mber of protons

Isotopes are atoms of the one element with different mass numbers with same atmoic number

-ide compounds contain two named elements, -ite + -ate compounds contain oxyen as well as the two na,ed elements.

Covalent Bonding

• in forming a covalent bond atoms achieve the same electron arragement as an atom of a noble gas, stable.
• Usually only atoms of non-metal elements form covalent bonds.
• a molecule is a group of atoms held together by covalent bonds.
• a diatomic molecule contains two atoms joined together
• EG. hydrogen- H (2), Oxygen- O (2), Nitrogen- N (2), Chlorine- Cl (2)
• An Oxygen molecule has a double covalent bond;
• A nitrogen molecule has a triple covalent bond;
• the diatomic molecules of other elements consist of single covalent bonds.
• The Protons give a positive charge to the nucleus of the atom.
• The positive nuclei of both atoms attract the negative shared electrons and this holds the atoms together, Alot of energy is needed to break covalent bonds.

Fuels

• Are chemicals that burn (react with oxygen) releasing energy.
• An Exothermic reaction is o in which energy is released
• Fossil fuels are finite resources; cannot be replaced.

Fractional Distllation

is the process used to separate the different hydrocarbons in crude oil according to their boling points.

Nitrogen makes up approx 80% of air, oxygen makes up 20%.

Carbon Dioxide is formed in the complete combustion of fossil fuels. Carbon monoxide is a poisonous gas.

Catalyic converters in car exhausts convert harmful gases into harmless ones.

Alkanes

• CnH2n+2
• cardon to cardbon bonds - single covalent
• burned in a llimited supply of air carbon monoxide may be produced
• Cycloalkanes general formula is CnH2n (ring of carbon atoms)

Alkenes

• CnH2n
• carbon to carbon double covalent bond
• undergo addition reactions with hydrogen & bromine (decolourises bromine)

Homologous series - set of compounds with the same general formula and similar chemical properties. Catalytic cracking is a process which breaks unwanted large molecules into smaller more useful molecules, alkenes are also produced.Catalyst speeds up reaction allowing it to take place at a lower temperature.