Electrons, Bonding Naming Compounds

ELECTRONS

Electron Arrangement

• Electrons travel in orbits around the nucleus (similar to planets around the sun)

– 1st orbit holds 2 electrons– 2nd orbit holds 8 electrons– 3rd orbit holds 18 electrons– In general the nth orbit can accommodate 2n2

• Atoms are ‘stable’ when they have full electron orbitals, therefore atoms gain or lose electrons, resulting in ions (charged particles)

EXAMPLE

• Lithium has 3 electrons, 2 of which are on the first level and the 3rd on the second level.

• We write this as (2,1)

3+

Some WEIRD STUFF• Say you have 21 electrons. You’d think you’d be

able to write it like (2, 8, 11).

• However, when filling the 3rd energy level once it hits 8 you put the other electrons in the 4th energy level till you have two.

• You can then start filling the 3rd energy level.

• So 21 electrons would be (2,8,9,2)

POSITIVE OR NEGATIVE

Atoms are ‘stable’ when they have full electron energy levels, therefore atoms gain or lose electrons, resulting in ions (charged particles)

Group 1 metals (Li, Na….) all tend to lose 1 electron (Li+, Na+)Group 2 metals (Be, Mg…) all tend to lose 2 electrons (Be2+, Mg2+)Group 7 elements (F, Cl…) all tend to gain 1 electron (F-, Cl-)Group 6 elements (O, S….) all tend to gain 2 electrons (O2-, S2-)

The Transitional metals all lose electrons to form positive ions.

CATION – are the ions with a positive chargeANION – are the ions with a negative charge

Predict the charge of;– Na Mg– Ca Al– Br S– N O

Na = 1+ Mg = 2+Ca = 2+ Al = 3+Br = 1- S = 2-N = 3- O = 2-

Bonding

The Octet Rule• As mentioned before:

– Atoms are ‘stable’ when they have full electron orbitals, therefore atoms gain or lose electrons, resulting in ions (charged particles)

• Therefore most Group A elements want to have either 2, 10, 18, 36, 54, or 86 electrons

1A 2A 3A 6A 7A 8A

H+

Li+

K+

Rb+

Cs+

Be2+

Mg2+

Ca2+

Sr2+

Al3+ O2-

S2-

Se2-

Te2-

F-

Cl-

Br-

I-

At-

HeNeArKrXe

There are 2 major types of bonding

1. Ionic bonding – When a metal gives one (or more) electron/s to a non-metal.

2. Covalent bonding – When two non-metals ‘share’ an electron.

Example of Ionic Bonding

Formulae for Ionic Formulae for Ionic CompoundsCompounds

• Aluminium oxide contains Al3+ and O2-.

• FORMULA: xA = yB– Where A is the charge on the cation and B is the charge on

the Anion.

• So X(3) = Y(2) ----- use the smallest numbers• X=2 and Y=3• So you’ll have 2 Al and 3 O == Al3O2

COVALENT BONDSCOVALENT BONDS• Easiest way to figure out covalent bonds is

through DOT Diagrams.• The number of dots around the element is

determined by what GROUP it’s in:

• The elements in the groups 3 and up want to have 8 electrons (dots) around them

11 22 33 44 55 66 77 88Li Be B C N O F Ne

Single Covalent bondSingle Covalent bond

ClCl ClCl

I wish I had one more electron so I’d

have 8

I wish I had one more electron so I’d

have 8

HEY LETS SHARE AN ELECTRON EACH SO IT LOOKS LIKE WE”VE GOT 8 EACH !!!

DOUBLE Covalent bondDOUBLE Covalent bond

OO OO

HEY LETS SHARE 2 ELECTRONs EACH SO IT LOOKS LIKE WE”VE GOT 8 EACH !!!

Examples of Covalent Bonding

H

1. Explain the difference between ionic and covalent bonding with the use of diagrams

2. Determine whether each of the following compounds would contain ionic or covalent bonding

a. Lithium and chlorineb. Boron and brominec. Aluminium and iodined. Sulphur and oxygen

1. .Ionic bonding involves ‘donating and receiving’ electrons, whereas covalent bonding involves ‘sharing’ of electrons

2. .a. Ionicb. Covalentc. Ionicd. Covalent