Additional Chemistry Revision

mass and atomic number

the mass number of an element such as sodium can be found at the top of the symbol and this tells us the number of protons and neutrons.

the atomic number can be found at the bottom of the symbol and this shows us the number of protons which then shows us the number of electrons. 

for example:

23 Na 11

protons: 11

neutrons: 12

electrons: 11

relative charge and mass

relative charge of a proton: +1           relative mass of a proton: 1

relative charge of a neutron: 0           relative mass of a neutron: 1

relative charge of an electron: -1        relative mass of an electron: 0

shell configuration

the number of electrons that can fit into the shells:

shell 1 - maximum 2 electrons

shell 2 - maximum 8 electrons

shell 3 - maximum 8 electrons

as you go across a period, an electron is added (periodic table)

as you go down a group, a shell is added (periodic table)

electron configuration

sodium: Na = 2, 8, 1

argon: Ar = 2, 8, 8

bonding

ionic = non-metal element and a metal element bonded together

covalent = non-metal element and non-metal element bonded together

metallic = when a sea of free electrons that have come from the atoms in the metal bond 

ionic compounds

electrostatic attraction is the force that holds the ions together

ionic compounds have high melting and boiling points because it takes alot of enegery to break down the bonds because they have a strong attraction

ionic compounds can conduct electricity when molten or dissolved in water because free electrons are the there which can conduct electricity

simple covalent molecules

the forces between covalent molecules (intermolecular forces) are strong but can be broken due to a weak force of attraction

due to the attraction being weak, alot of enegry is needed to break down the bonds which means that covalent molecules have higher melting and boiling points

the forces between atoms in a covalent bond (intermolecular bonds) are strong but the forces are weak

giant covalent substances

diamond and sand are giat covalent substances

graphite is slippery and can conduct…