REVISION NOTES
IGCSE Edexcel Chemistry
1.4 The Periodic Table
1.4.1 Understand how elements are arranged in the Periodic Table:
- In order of atomic number
- In groups and periods.
Elements on the periodic table are arranged in order of increasing atomic number.
GROUPS
- Vertical columns in the table
- Group number shows the number of valence (outermost shell) electrons
- E.g. elements in group 2 have 2 electrons in the valence shell
- The final group is called group 18 or 8 or 0
PERIODS
- Horizontal rows in the table
- Period number shows the number of electron shells in an atom
- E.g. elements in period 2 have two electron shells
1.4.2 Understand how to deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table
Deducing total number of electrons
- Number of electron = number of proton = atomic number (for an atom)
Each electron shell can accommodate a fixed number of electrons
- 1st shell: 2 electrons
- 2nd shell: 8 electrons
- 3rd shell: 8 electrons
Electronic Configuration of First 20 Elements
1.4.3 Understand how to use electrical conductivity and the acid-base character of oxides to classify elements as metals or non-metals
1.4.4 Identify an element as a metal or a non-metal according to its position in the Periodic Table
In general,
- Metals are on the left of the periodic table
- Non-metals are on the right of the periodic table
- They are separated by metalloids (semimetals) which form a zig-zag line
1.4.5 Understand how the electronic configuration of a main group element is related to its position in the Periodic Table
Period number: number of electron shells
Group number: number of electrons in the outer shell
1.4.6 Understand why elements in the same group of the Periodic Table have similar chemical properties
- The chemical properties of an element depend on the number of electrons in the outer shell
- Elements in the same group have same number of electrons in the outer shell
- Therefore, elements in the same group have similar chemical properties
1.4.7 Understand why the noble gases (Group 0) do not readily react
- Noble gases (group 0) have 8 electrons in their outer shell (except for helium, which has 2)
- Noble gases reach octet rule, meaning that they have full electron shells
- They do not lose or gain electrons easily
- Therefore, they are unreactive and do not easily form molecules
