Chemistry - atoms, electron structure, alkali metals and halogens, ionic bonding, covalent bonding, covalent structures

ATOMS!

Atom Charge
proton +
neutron -
electron n/a

No overall charge because there are equal numbers of postive protons and negative electrons.

4
He
2
Atomic number is the smaller number.
Mass number is always the bigger of the two - massive mass number.

Number of neutrons = mass - atomic number
4
He = 4 - 2 = 2 neutrons.
2

ELECTRON STRUCTURE!

Inner ring can have 2 electrons,
Further outer rings can have up to eight.

Example: Oxygen.
Has 2 electrons in inner ring, then 6 on the outer ring.

Note to readers: The alkali metal and halogens card leads on from this one.

:)

ALKALI METALS AND HALOGENS!

Alkali metals:
+ 1 electron in their outer shell
+ react with a non-metal element to form ionic compounds with a postive charge. (+)

Halogens:
+ 7 electrons in their outer shell
+ react with an alkali metal to from ionic compounds.

Mixtures and compounds:
Mixtures - two or more elements that are not chemically combined.
Compounds - two or more elements that are chemically combined.

IONIC BONDING & COVALENT BONDING!

Ionic bonds:
- high melting and boiling points.
- strong bonds therefore conduct electricity.
- between a postive and negative.
+metal and non-metal.
- transfer of electrons (e-)
-atoms become postive if they loose e-.
-atoms become negative if they gain e-.
Covalent bonds:
- weak
- between two non-metals
- dot and cross diagrams
- strong bonds formed when e- shared.
- sharing of electrons.

COVALENT STRUCTURES!

- very strong bonds therefore very high melting point.
- metals, layers can be bent and shaped.
- Diamonds
+ lattice structure
+ each carbon atom forms 4 bonds.
+ lots of bonds, very strong and hard.
+ not easily shaped.
- Graphite
+ only form 3 bonds.
+ layered structure
+ form of carbon
+ 1 electron is delocalised so graphite can conduct electricity and heat.
+ layers can slide past each other - soft and slippery.