Learning check
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The alkali metals
The alkali metals are found to the far left in the periodic table.
The alkali metals are:
- (Hydrogen, H)
- Lithium, Li
- Sodium, Na
- Potassium, K
- Rubidium, Rb
- Cesium, Cs
- Francium, Fr
Alkali metals have one valence electron. Example: 3Li
| K | L | |
| 3p+ | 2e– | 1e– |
Oxidation of alkali metals
Alkali metals give off their single valence electron.
When sodium is oxidized, it loses an electron and turns into a sodium ion, Na+.
When the alkali metal atom is oxidized, it gets
- a single positive charge, e.g. Na+.
- noble gas configuration (eight valence electrons).
The most reactive alkali metal
The furter away from the nucleus,
- the easier it is to release the valence electron
- the less energy is needed for ionization (the lower ionization energy).
The reactivity increases downwards in group 1:
- In francium, the valence electron is in the 7th shell ⇒ very easily given off!
- In lithium, the valence electron is in the 2nd shell ⇒ not given off as easily.
The halogens (salt producers)
Metals readily react with halogens, producing salts.
- Example: Sodium reacts with chlorine
2Na + Cl2 → 2NaCl
The halogens are found in group 17 of the periodic table.
The halogens are:
- Fluorine, F
- Chlorine, Cl
- Bromine, Br
- Iodine, I
- Astatine, At
- Tennessine, Ts
Halogens have seven valence elctrons. Example: 9F
| K | L | |
| 9p+ | 2e– | 7e– |
Reduction of halogens
Halogens take up an electron to get noble gas configuration.
When chlorine is reduced it gains an electron and turns into a chloride ion, Cl–.
When the halogen atom is reduced, it gets
- a single negative charge, e.g. Cl–.
- noble gas configuration (eight valence electrons).
The most reactive halogen
The closer to the nucleus
- the easier it is to take up an electron
- the more energy is given off when that electron is taken up.
The reactivity increases upwards in group 17:
- In fluorine, the valence electrons are in the 2nd shell ⇒ very easily takes up an electron!
- In iodine, the valence electrons are in the 5th shell ⇒ electrons aren’t taken up as easily.
