1. Group 1
Noadswood Science, 2016

2. Group 1 To know the properties of Group 1 – the alkali metals
Tuesday, June 05, 2018
Group 1
To know the properties of Group 1 – the alkali metals

3. Precise Learning
The elements in Group 1 of the periodic table are known as the alkali metals and have characteristic properties because of the single electron in their outer shell.
Students should be able to describe the reactions of the first three alkali metals with oxygen, chlorine and water.
In Group 1, the reactivity of the elements increases going down the group. Students should be able to:
explain how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms
predict properties from given trends down the group.

4. Reactivity
Some metals are extremely reactive, whilst others are not – the reactivity series shows how reactive metals are…
Potassium
Sodium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
Lead
(Hydrogen)
Copper
Silver
Gold
Platinum

5. Reactivity
Compare the reactivity series to where the elements are found within the periodic table – what relationship is there?

6. Electron Structure & Reactivity
There is a definite pattern between the placement of a metal on the periodic table and how reactive it is – the most reactive metals are located in groups I and II, with the least reactive metals being within the transition metals, placed in the centre of the periodic table, between groups II and III – they are generally hard and dense, and less reactive than the alkali metals

7. Reactivity – Very Reactive
The electron structure of an atom affects how reactive it is – a shell with just one electron in is it keen to ‘get rid’ of this so they have a full outer shell
Elements within group I (lithium, sodium, potassium etc…) and group II (magnesium, calcium, strontium etc…) have just one or two electrons to ‘get rid of’ before they have a full outer shell, and as such are extremely reactive
The most reactive metals are found within group I and II

8. Shells
Electrons which orbit the nucleus of an atom occupy specific shells – the follow some specific rules: -
Electrons always occupy shells (energy levels)
The lowest energy levels are always filled up first
Only a certain number of electrons are allowed in each shell (1st shell = 2; 2nd shell = 8; 3rd shell = 8; 4th shell = 18)
In most atoms the outer shell is not full, making them want to react

9. Electron Structure
The electronic structure of an atom is a description of how the electrons are arranged - you need to be able to describe the electronic structure of the first 20 elements in the periodic table...
The first 20 elements in the periodic table run from hydrogen to calcium

10. Electron Structure
The periodic table can be used to work out an electronic structure: -
Find the element in the periodic table
Work out which period it is in, and draw that number of circles around the nucleus
Work out which group the element is in and draw that number of electrons in the outer circle - with eight for Group 0 elements (except helium)
Fill the other circles with electrons (2 in the first, 8 in the second and third, and 18 in the fourth)
Finally, count your electrons and check that they equal the atomic number

11. Lithium
For example, work out the atomic structure of Lithium...

12. Lithium
Lithium - 2nd period so it has 2 circles drawn around it and in group 1 so it has 1 electrons in the outer shell...

13. Lithium
Lithium (Li) - 2,1 (three electrons (2 in shell 1 and 1 in shell 2))

14. Alkali Metals
Elements in group 1 are known as the alkali metals – they are very reactive and have the following properties as you go down the group: -
They become more reactive (outer e- further from nucleus)
They have lower melting points
 They have lower boiling points
They have a low density (Li, Na and K less dense than water)

15. Alkali Metals & Water
Alkali metals react vigorously with water, producing hydrogen gas and form hydroxides that dissolve producing alkaline solutions
2Na (s) + 2H2O (l)  2NaOH (aq) + H2 (g)
2K (s) + 2H2O (l)  2KOH (aq) + H2 (g)

16. Alkali Metals & Oxygen
Alkali metals can react with oxygen to form a metal oxide – different types of oxide will form depending on the Group 1 metal, for example: -
Lithium reacts to form lithium oxide
4Li (s) + O2 (g)  2Li2O(s)
Sodium reacts to form a mixture of sodium oxide (first equation) and sodium peroxide (second equation)
4Na (s) + O2 (g)  2Na2O(s)
2Na (s) + O2 (g)  Na2O2 (s)

17. Alkali Metals & Oxygen
Alkali metals can react with oxygen to form a metal oxide – different types of oxide will form depending on the Group 1 metal, for example: -
Potassium reacts to form a mixture of potassium peroxide (first equation) and potassium superoxide (second equation)
2K (s) + O2 (g)  2K2O2 (s)
K (s) + O2 (g)  KO2 (s)

18. Alkali Metals & Chlorine
Alkali metals react vigorously with heated with chlorine gas to form white metal chloride salts
Alkali metal + chlorine  metal chloride
2Li (s) + Cl2 (g)  2LiCl (s)
2Rb (s) + Cl2 (g)  2RbCl (s)

19. Practice Questions
Which group in the periodic table are the alkali metals?
Do the alkali metals have low density or high density?
State the trend in reactivity as you go down Group 1
What type of bonds do alkali metals form during reactions with non-metals?
Write down the general word equation for an alkali metal + water
Name the compounds that form when potassium reacts with oxygen

20. Answers Group 1 Low density Reactivity increases Ionic bonds
alkali metal + water  metal hydroxide + hydrogen
Potassium superoxide + potassium peroxide