Group 2-AlkalineEarth Metals Flashcards
Electrons in outer shell
Ions formed in reactions
Group 2 elements all have two elements in their outer shell (s2).
Lose two outer electron to form 2+ ions
Trend in atomic radius
Why?
Atomic radius increases down group 2.
Extra electron shells are added as you go down the group
Trend in first ionisation energy
Explain
First ionisation energy decreases down group 2.
Each element down group 2 has extra electron shell compared to the one above. Extra inner shells shield outer electrons from attraction of the nucleus.
The extra shell means outer electrons are further away from the nucleus, which greatly reduces the nucleus’s attraction
Positive charge of nucleus down group 2 and first ionisation energy
The positive charge of the nucleus does increase as you go down a group (due to extra protons),
But this effect is overridden by the effect of the extra electron shells
Trend in reactivity down group 2
Explain
Reactivity increases down group 2.
As you go down, first ionisation energy decreases.
This is due to increasing atomic radius and shielding effect.
Easier it is too lose the two electrons the more reactive the element
Trend in melting points down group 2
Explain
One exception and explain
Melting points generally decrease down group 2
Typical metallic structures.
Ions get bigger down the group. But number of delocalised electrons doesn’t change and neither does the charge on the ion.
Larger ionic radius means further away delocalised electrons are from positive nuclei so less nuclear attraction.
Takes less energy to break the bonds.
Magnesium, due to crystal structure (arrangement of metallic ions) changes
Reactions with water
What is the oxidising agent?
Why react more readily down group 2?
Group 2 metals react with water to give a metal hydroxide and hydrogen.
Water is the oxidising agent (accepts electrons and gets reduced).
Ionisation energies decrease down group 2
