C3.01 The number of elements
Number of elements = about 100
Elements are building bricks of all materials
C3.02 The order of elements in the periodic table
Elements are placed in order of increasing atomic number so
hydrogen atomic number 1 is first
helium atomic number 2 is second etc.
| 1 hydrogen | 2 helium | |||||||
| 3 lithium | 4 berylium | 5 boron | 6 carbon | 7 nitrogen | 8 oxygen | 9 fluorine | 10 neon | |
| 11 sodium | 12 magnesium | 13 aluminium | 14 silicon | 15 phosphorus | 16 sulphur | 17 chlorine | 18 argon |
Elements in a row e.g. sodium to argon are called a period.
C3.03 Groups
A group is a column of elements with similar properties in the periodic table. See figure
1. e.g all of the following are in the same group and are silver in colour,
soft and good conductors of electricity.
| lithium |
| sodium |
| potassium |
| rubidium |
| caesium |
C3.04 The position of groups in the periodic table
The positions of the alkali metals (group 1), the halogens (group 7), the
noble gases (group 0) and the transition metals are shown in figure
1 above.
Task C3.04 Label a copy of the periodic table to show
a group, a period, the alkali metals, halogens, noble gases, transition metals,
metals, and non-metals.
C3.05 Outer electrons and position in the periodic table
|
number of outer electrons |
position in periodic table |
| 1 | group1 alkali metals |
| 2 | group 2 |
| 3 | group 3 |
| 4 | group 4 |
| 5 | group 5 |
| 6 | group 6 |
| 7 | group 7 halogens |
| 8 | group 0 noble gases |
C3.06 Reactions and electron arrangements
Group 1 elements all have atoms with 1 outer electron. e.g. sodium 2,8,1
All of these atoms try to lose 1 electron so all react in the same way.
They all form a positive ion and form ionic compounds. E.g. sodium Na form
sodium ion Na+.
Group 1 elements all react with oxygen (that is burn) to form oxides. The products
like sodium oxide, are all ionic. see sodium burn
Group 0 elements all have atoms with complete outer shells e.g. helium 2, neon
2,8. None of these elements react with anything.
Task C3.06 Name other elements in group 1 and say how they
react with oxygen giving a reason. State how argon reacts with oxygen and
give a reason.
C3.07 Trends in group properties
Group 1 elements get more reactive with water as you go down the group. e.g.
Lithium (gentle fizz) is less reactive than potassium (violent lilac flame).
Group 7 elements get more reactive with iron as you go up the group.
Iodine darkens iron when it is heated but chlorine makes iron burst into flames.