2.3.2Additional lessons
s and p Block Elements — IB Chemistry SL Revision Notes & Topical Questions
5 min read 6 parts Lesson 34 of 98
Part 1 of 6Blocks of the Periodic Table
The shape of the periodic table reflects the order in which sublevels are filled.
s block
- Elements whose highest-energy electron is in an s sublevel: Groups 1 and 2, plus hydrogen and helium.
p block
- Elements filling a p sublevel, which are Groups 13 to 18 (helium is excluded).
d block
- Elements filling a d sublevel, which are the transition region between Groups 2 and 13.
Reading position
- The block of an element shows which type of sublevel contains its valence electrons.
Part 2 of 6Metals and Non-Metals
Metals and Non-Metals
s block metals
- Groups 1 and 2 are all metals with low ionisation energies, whose atoms readily lose their valence electrons.
p block metals
- Aluminium, tin and lead are p block metals, showing that metallic character is not limited to the s block.
p block non-metals
- Carbon, nitrogen, oxygen, the halogens and noble gases are non-metals on the right of the table.
Metalloids
- Elements such as silicon and germanium lie near the boundary and have properties between metals and non-metals.
Part 3 of 6Trends in Melting Point
1
Down Group 1 the metal ions get larger while still contributing one electron each, so metallic bonding weakens.
2
Melting points therefore fall from lithium (181 °C) to sodium (98 °C), potassium (63 °C), rubidium (39 °C) and caesium (28 °C).
3
Across period 3, sodium, magnesium and aluminium contribute one, two and three electrons per atom with smaller ions, so melting points rise.
4
Silicon forms a giant covalent network and has a very high melting point of 1414 °C.
5
The non-metals phosphorus, sulfur and chlorine form small molecules held by weak forces, so melting points drop sharply.
| Group 1 metal | Melting point / °C |
|---|---|
| Li | 181 |
| Na | 98 |
| K | 63 |
| Rb | 39 |
| Cs | 28 |
Part 4 of 6Connecting Block to Properties
Low density metals
- Group 1 metals are soft and have low densities, which is why they are stored under oil.
Group 2 metals
- These are harder and have higher melting points than Group 1 neighbours because each atom provides two electrons.
Valence electrons
- For s and p block elements the group number reveals the number of valence electrons.
Reactivity
- Reactivity of metals increases down a group while reactivity of non-metals decreases down a group.
Part 5 of 6Worked Example
Question State the block and group of an element with electron configuration 1s²2s²2p⁶3s², and name the type of bonding it would have in the solid.
- The last electrons go into the 3s sublevel, so the element is in the s block.
- It has two valence electrons in shell 3, so it is in Group 2, Period 3, which is magnesium.
- As a metal in the solid state it has metallic bonding.
Answer
- s block, Group 2 (magnesium);
- metallic bonding in the solid.
Part 6 of 6Exam Checklist & Tips
2.3.2 – Key Points for the Exam
- s block Elements in which the highest-energy electrons occupy an s sublevel.
- p block Elements in which the highest-energy electrons occupy a p sublevel.
- Metalloid An element with properties intermediate between metals and non-metals.
- Valence electrons Electrons in the outermost shell of an atom.
Common Mistakes
- Placing helium in the p block; it is in the s block despite its position in Group 18.
- Assuming all metals are in the s block.
- Saying melting points rise down Group 1; they fall.
- Forgetting that silicon, unlike Mg and Al, is a covalent network.
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