1c) Atomic structure

Nucleus- contains neutrons and protons
Protons- has a positive charge due to neutrons
Electrons- move around the nucleus in shells; negatively charged
2,8,8,2: Elements in the same group have the same number of outer shell electrons

Atoms consist of a nucleus in the centre, which has neutrons and protons. Protons have a positive charge due to neutrons. There are also electrons which move around the nucleus in shells and are negatively charged. Elements in the same group have the same amount of outer shell electrons.

Particle	Relative Mass	Relative Charge
Proton	1	+1
Neutron	1	0
Electron	1/2000	-1

• Atomic Number tells you how many protons there are
• Mass number is the total number of protons and neutrons in an atom
• Isotopes have the same chemical reactivity but different number of neutrons they also have the same molecular formula but different structural formula.
• The Relative atomic mass (Ar) is the average mass of all the isotopes of an element. It allows for the relative mass of each isotope and its relative abundance.
• Relative Abundance is how much there is of each isotope compared to the total amount of the element in the world. This can be represented as a ratio, fraction or percentage.

The Periodic Table

Is an arrangement of elements in order of their atomic number

Electronic configurations of the 1^st twenty elements

Element	Electronic Configuration
Hydrogen	1
Helium	2
Lithium	2,1
Berylium	2,2
Boron	2,3
Carbon	2,4
Nitrogen	2,5
Oxygen	2,6
Fluorine	2,7
Neon	2,8
Sodium	2,8,1
Magnesium	2,8,2
Aluminium	2,8,3
Silicon	2,8,4
Phosphorus	2,8,5
Sulphur	2,8,6
Chlorine	2,8,7
Argon	2,8,8
Potassium	2,8,8,1
Calcium	2,8,8,2