Group 2: ionisation energy and properties
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Explainer Video
Summary
Group 2: ionisation energy and properties
In a nutshell
As you go down Group in the periodic table, the atomic radius and reactivity increase, whilst the ionisation energy and melting points decrease for Group metals.
Electron configuration
Element | Atom | Ion |
| | | |
| | | |
| | | |
As Group elements react, they tend to lose their two outermost electrons and form ions.
Atomic radius
For Group elements the atomic radius decreases as you go down the group. This is because electron shells are added as you go down the group which causes an increase in radius.
First ionisation energy
For Group elements as you go down the group an extra electron shell is added. The inner shells shield the outer shell from the nucleus. This weakens the attraction of the outer electrons to the nucleus making them easier to remove. Thus, decreasing the first ionisation energy as you go down the group.
Reactivity
As you do down Group , reactivity increases. This is due to the first ionisation energy decreasing as you go down the group. Since less energy is required to remove the outermost electrons as you go down the group, this means it's easier for the metals to react. Therefore reactivity of the Group metals increases down the group.
Melting points
Group metals have metallic structures with positive ions surrounded by delocalised electrons. Going down the group the metal ions get bigger, but the charge remains the same, . This means that charge density decreases resulting in a weaker attraction between atoms. This means less energy is required to separate the atoms.
Group 2 and water
When Group elements react with water they are oxidised and their oxidation number changes from to . This forms ions.
Example
FAQs - Frequently Asked Questions
How does the reactivity change as you go down Group 2?
The reactivity increases down Group 2. This is due to lower ionisation energy which means less energy is required to cause the Group 2 metals to react.
How does the ionisation energy change as you go down Group 2?
As you go down Group 2 the ionisation energy decreases. This is due to the atomic radius and the shielding effect.
What sort of ions do Group 2 metals normally form?
Group 2 metals normally form 2+ ions in compounds (M^2+). Group 2 metals lose their two outermost electrons.