ATOMIC STRUCTURE

Atoms - Neutrally charged

Ions - Positively charged (cation) or negatively charged (anion)

Nucleon number - Total protons and neutrons in an atom.

Particles - May be atoms, molecules, or ions.

Isotopes - Atoms of an element with the same number of protons and electrons but different number of neutrons.

Radioisotopes - Isotopes which emit high-energy radiation.

Electro-positive - Tendency to lose electrons

Discharge - To lose charge

ATOMS

No of orbitals in an atom = 2n^2 (n being the shell number)

E.g. How many electrons are present in the 3rd shell of an atom?

2 x (3)^2

2 x 9

= 18 electrons

MAIN ENERGY LEVELS

(1) K = 2 electrons

(2) L = 8 electrons

(3) M = 18 electrons

(4) N = 32 electrons

(5) O = 50 electrons

Sub-energy levels SPDF make up the main energy levels. Each sub-level can only hold a certain number of electrons.

S = 2 electrons

P = 6 electrons

D = 10 electrons

F = 14 electrons

Duplet rule: A maximum of 2 electrons can be present in the first shell of any atom

Octet rule: A maximum of 8 electrons can be present in each shell after the first shell for the first 20 elements.

Figure 1. Shells in an atom

Figure 2. Duplet and Octet rule

Valence Shell - Furthest away from the nucleus (chemical properties of the atom depend mainly on bonds formed by electrons in valence shell)

Electrons fill the orbit in a specific pattern, as can be seen in the image given below:

Figure 3. Electronic Configuration

E.g. Na has the atomic number 11. This can be written as:

2, 8, 1. To gain octet form, Na will have to lose one electron, making it one positive (+1).

O is in group 16 (AKA 6), and has the atomic number 8. This can also be written as:

2, 6. To gain octet form, O will have to gain two electrons, making it two negative (2+).

Figure 4. The periodic table