1. The Physical and Chemical Properties of the Group 1 elements
Lithium Atomic Number 3 Mass Number 7
Sodium Atomic Number 11 Mass Number 23
Potassium Atomic Number 19 Mass Number 39
Rubidium Atomic Number 37 Mass Number 86
Caesium Atomic Number 55 Mass Number 133
What is the number of protons, electrons and neutrons for each element?
What is the electronic configuration for the first three elements?
Why are the elements all in group 1?

2. ANSWERS Element Lithium 3 4 2,1 Sodium 11 12 2,8,1 Potassium 19 20
protons
neutrons
electrons
arrangement
Lithium 3 4
2,1
Sodium 11 12
2,8,1
Potassium 19 20
2,8,8,1
Rubidium 37 49
2,8,18,8,1
Caesium 55 78
2,8,18,18,8,1
ALL HAVE 1 electron in outer shell

3. Physical Properties
Melting Points
Density
Hardness

4. Melting Points I Lithium 180oC Sodium 98oC Potassium 630C
Rubidium 39oC
Caesium 29oC
What is surprising about the melting points of these elements? ( Melting Points of Al 6600C, Fe 1540oC, Cu 1084oC)
What does this tell you about the bond between the atoms in each of the group 1 elements?
What is the trend in melting point?

5. Melting points II
All have Low melting points. Metals usually have HIGH melting points
They must have weak forces of attractions (bonds) between the atoms.
(METALLIC BOND IS WEAK IN GROUP ONE METALS)
Melting points decreases down group

6. Densities I Lithium 0.5 g/cm3 Sodium 0.97 g/cm3 Potassium 0.86 g/cm3
Rubidium 1.5 g/cm3
Caesium 1.9 g/cm3
What is surprising about the densities of these elements? ( Densities of Al 2.7g/cm3, Fe 7.9g/cm3, Cu 8.9g/cm3)
What is the trend in density?

7. Densities II
All have Low densities. Metals usually have HIGH densities
The atoms must be Loosely packed together
Density increases down group. .

8. HARDNESS II All are soft and can be cut with a knife
Metals are usually hard.
Hardness decreases down group.
It becomes easier to cut them up

9. Chemical Properties Corrosion – oxidation in air
Reaction with pure Oxygen
Reaction with water
See video on Firefly Group 1 elements

10. Reaction with Water II
As before, Reactivity increases down the group as illustrated by
Metal moves much faster
After Na, the Hydrogen catches fire so more energy must be given off
After K, Explosions occur
Alkali containing Sodium = Sodium Hydroxide
Formula of Sodium Hydroxide = NaOH.

11. Reaction with Water III
SODIUM AND WATER  SODIUM HYDROXIDE AND HYDROGEN
2Na + 2H2O  2NaOH + H2
Equations for other metals
2M + 2H2O  2MOH + H2
(Swap symbol of metal with the M above)

12. Reasons for reactivity
NB Full outer shell = stable atom
NB In reactions atoms lose/gain or share electrons to achieve full outer shell
NB Group 1 elements have 1 electron in their outer shell
SO to achieve full outer shell they:
LOSE ONE ELECTRON during reactions.

14. Reasons for reactivity
Further the electron in outer shell is from the nucleus the easier it is to lose.
Inner shells SHIELD (dilute) effect of nucleus.
(Think about putting sheets of paper between two magnets, force decreases)

15. Uses of Sodium and Compounds