Group 2- The Alkaline Earth Metals Flashcards
Why does atomic radius increase down group 2
Because of the extra electron shells as you go down the group
Group 2 elements lose ….. electrons when they react
2, they have 2 electrons in their outer shell. They lose their 2 outer electrons to form 2+ ions. Their ions then have the structure of a noble gas
Why does ionisation energy dresses down group 2
Each element in group 2 has an extra electron shell compared to one above. The extra inner shells shield the outer electron from the attraction of the nucleus. Also, the extra shell means that the outer electrons are further away from the nucleus, which greatly reduces the nucleus’s attraction. Both of these factors make it easier to remove outer electrons, resulting in a lower IE. 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 shells.
Why does reactivity increase down group 2
As you go don group, IE decrease, due to increasing atomic radius and sheilding. When group 2 elements react they lose electrons, forming positive ions. The easier it is to lose electrons, the more reactive the element so reactivity increases down the group
Why does melting point generally decrease down group 2
Group 2 elements have typical metallic structures, with the electrons of their outer shells being delocalised. Going down the group the metallic ions get bigger, so have smaller charge/volume ratio. But number of delocalised electrons per atom doesn’t change. So the delocalised electrons get more spread out. These 2 factors mean there’s reduced attraction of the positive ions to the sea of delocalised electrons, so less energy needed to break bonds so lower MP. However ‘blip’ at magnesium as crystal structure changes
Do group 2 metals react with water
Yes
What happens when group 2 metals react
They are oxidised from a state of 0 to +2, forming 2+ ions
What are the products when a group 2 metal reacts with water
A metal hydroxide and hydrogen
Explain solubility in group 2 elements
It depends on the compound anion. Generally the elements contain singly charged negative ions (eg OH-), increase in solubility down the group. Whereas compounds that contain double charged negative ions (eg SO4 2-) decrease in solubility down the group
Compounds like magnesium hydroxide which have very ……. solubilities are said to be….
Low
Sparingly soluble
Most sulphites are soluble in water, but ……….. ………. is insoluble
Barium sulphate
What is the test for sulphate ions
Acidified barium chloride is added to a solution containing sulphate ions then a white precipitate of barium sulphate is formed.
You need to acidify the barium chloride (with HCl) to get rid of any sulphites or carbonates
What are group 2 compounds used for
Neutralise acidity
What does calcium hydroxide do
Used in agriculture to neutralise acidic soils
What does magnesium hydroxide do
Used in some indigestion tablets as an antacid
