27th April '09

[IONISATION ENERGY]: is the minimum energy required to remove one mole of electrons from one mole of gaseous atoms/ions to form one mole gaseous cations.

[FIRST IE]: The removal of one mole of electrons from one mole of gaseous atom to form one mole of singly-charged gaseous ion.

[SECOND IE]: The removal of one mole of electrons from one mole of singly-charged gaseous ion to form one mole of doubly-charged gaseous ion.

SUBATOMIC PARTICLES

- atoms are made up of protons, neutrons & electrons
- protons + neutrons = nucleons
& are found in dense (+)vely charged nucleus
- electrons are very light & are (-)vely charged

PROTON & NUCLEON NUMBER

* A= no. of protons + neutrons (no. of nucleons)
* Z= no. of electrons (atomic no./proton no.)
*A-Z= no. of neutrons

- Isotopes are atoms of the same element but with different number of neutrons
- Isotopes have the same chemical properties but different physical properties

- ISOELECTRONIC are atoms/ions that have the same no. of electrons

GROUND STATE: Atom has its electron in the lowest available energy level
EXCITED STATE: Electron absorbs energy to move to higher energy level

* When electron returns to a lower energy level, it gives out excess energy as LIGHT.

S, P, D, F ORBITALS

S ORBITALS: SPHERICAL SHAPED; NO DIRECTION
P ORBITALS: DUMB-BELL SHAPED; 3 DIRECTIONS (Px, Py, Pz)

in n^th shell, there are..
n subshells
(n)(n) orbitals
2(n)(n) of maximum electrons

SHELLS

when n=1,
No. of orbitals= 1
Max number of electrons= 2
S P D F
1 - - -

when n=2,
No. of orbitals= 4
Max number of electrons= 8
S P D F
1 3 - -

when n=3,
No. of orbitals= 9
Max number of electrons= 18
S P D F
1 3 5 -

when n=4,
No. of orbitals= 16
Max number of electrons= 32
S P D F
1 3 5 7

3 different laws when figuring the electronic configuration of an element

(1) Aufbac Principal
* the added electron always occupy the orbital with the lowest energy level

(2) Pauli Exclusion Principal
* each orbital can hold a max of 2 electron of opposite spin

(3) Hund's Rule of Multiplicity
* when filling a sub-shell, each orbital must be occupied singly before they are occupied in pairs

EXAMPLES OF S,P,D,F NOTATIONS:

i) F: 1s2 2s2, 2p5
ii) N: 1s2, 2s2, 2p3

NOBEL GAS CORE

iii) N: [He] 2s2, 2p3,
* Noble gas He represents 1s2 as there are 2 electrons in element Helium.