Electrons: Negative Charge
Neutrons: Neutral Charge (have the same ammount of protons and electrons)
Protons: Positive Charge
Each shell around the nucleus can have a set number of electrons. Here is the list you need to know:
Shell & Max Number of Electrons
First Shell = 2
Second Shell = 8
Third Shell = 8
Fourth Shell = 2
Atomic and Mass Numbers
Atomic Number (proton number): Number of Protons and Electrons.
Work this out by simply looking at the number.
Mass Number (bigger one): Number of Neutrons.
Work ths out by taking the Atomic Number away from the Mass Number. For example:
Number of Neutons in Helium: 4 - 2 = 2
Electron Structure & Questions
Period (the row): This tells you the number of shells filled.
Group Number: Number of outer electrons.
1) 2.5 = Nitrogen (Period 2, Group 5)
2) 2.8.6 = Sulphur (Period 3, Group 6)
3) 220.127.116.11 = Calcium (Period 4, Group 2)
Group 1 Metals
- All stored in oil
Reactions with water:
Lithium - Fizzing, floats on top (less dense), releases smoke/steam.
Sodium - Fire, fizzing, floats on top (less dense), melts into metal, popping noise.
Potassium - Fire, sparking, buzzing noise.
All make an alkali solution!
Reactions with oxygen:
Lithium - Glows red.
Sodium - Glows orange.
Potassium - Glows lilac
- They are noble gases.
- Colourless gases.
- Very unreactive because they have 8 outer shell except for Helium.
- They have enough electrons so they do not need to react.
Chemical Bonds: The Basics
When 2 or more atoms joing together chemical bonds are made. Chemical bonds can be made when:
- Atoms lose or gain electrons
- Atoms share electrons
Chemical Bonds: Ions & Covalent Bonds
- Metal atoms LOSE ELECTRONS to form POSITIVE IONS.
- Non metal atoms GAIN ELECTRONS to form NEGATIVE IONS.
- Ions form because there is an uneven ammount of electrons.
- Attraction between the ions that are made are called ionic bonds.
Convalent: Non metal atoms like hydrogen each share an electron to form a bond.
Chemical Bonds: Summary and Balancing Equations
Balancing Equations on sheet.