Chemistry C3 GCSE Revision Notes OCR (higher)

THE ATOMIC STRUCTURE

Particle                                        Charge                                        Mass

Proton                                              +                                                1
Neutron                                            0                                                1
Electron                                            -                                            1/2000

Atoms are neutral

Isotopes
-atoms of the same element with a different mass

For every 4 atoms of chlorine, 1 is heavier.

What makes atoms reactive?
-They want to obtain a full outer shell.

 <---Shared Pair of electrons from each Hydrogen atom.

H-H or H2

  <--Sharing of electrons between two Hydrogen molecules and one oxygen, to make water.

H-O-H or H20

<--- Sharing of electrons between 4 hydrogen atoms, and one carbon atom, creating methane.

CH4 or   H
              |
        H - C - H
              |
              H

<--- In Oxygen a double bond is used (the sharing of two pairs of electrons)

O2 or O=O

GROUP 1 METALS - ALKALI

Li - Lithium
Na - Sodium
K - Potassium
Rb - Rubidium
Cs - Caesium

They increases in size (mass) as you go down the group.
Eg…