Group 2 Flashcards
What are the elements in Group 2 called?
Alkaline earth metals
Why are the group 2 elements called alkaline earth metals?
Alkaline properties of the metal hydroxides - reactive and don’t occur in their elemental form naturally
What are Group 2 elements found in on earth?
Stable compounds
What is the most common type of reaction in Group 2 elements?
Redox reactions
How many outer-shell electrons does each Group 2 element have?
Two
What is the outer-most subshell in Group 2?
Outer s subshell
What happens during a redox reaction with Group 2 elements?
Each metal atom is oxidised, losing two electrons to form a 2+ ion with the electron configuration of a noble gas
Another species will gain these two electrons and be reduced
What does the Group 2 element become in a redox reaction?
A reducing agent
Why does the Group 2 element become a reducing agent?
It has reduced another species
What do Group 2 elements form when reacting with oxygen?
A metal oxide
What is the general formula of a metal oxide?
MO
What ions are in a metal oxide?
M2+ and O2- ions
What happens when magnesium reacts with oxygen?
Magnesium burns with a brilliant white light and forms white magnesium oxide
What happens to the oxidation number when metals react with oxygen?
They balance
What do Group 2 elements form when reacting with water?
An alkaline hydroxide and hydrogen gas
What is the general formula of an alkaline hydroxide?
M(OH)2
What is the trend in reactivity in Group 2?
Reactivity increases down the group
What do Group 2 elements form when reacting with dilute acids?
A salt and hydrogen gas
How do Group 2 elements react?
By losing electrons to form 2+ ions
What does the formation of 2+ ions from gaseous atoms require?
The input of two ionisation energies
What is the trend in ionisation energies down Group 2?
Ionisation energies decrease down the group
Why do ionisation energies decrease down Group 2?
The attraction between the nucleus and outer electrons decreases as a result of increasing atomic radius and shielding
Why do Group 2 elements become more reactive down the group?
The ionisation energies decrease so it becomes easier to remove an electron from the outer shell
What happens when Group 2 oxides react with water?
They release hydroxide ions (OH-) and form alkaline solutions of the metal hydroxide
Are Group 2 hydroxides soluble in water?
Only slightly
What happens when a Group 2 hydroxide solution becomes saturated?
Any further metal and hydroxide ions will form a solid precipitate
What is the trend in solubility of hydroxides down Group 2?
It increases down the group
What happens to resulting solutions down the group?
They contain more OH- (aq) ions and are more alkaline
Describe the experiment to show the trend in solubility of Group 2 hydroxides
1) Add a spatula of each G2 oxide to water in a test tube
2) Shake. On this scale, there is insufficient water to dissolve all the metal hydroxide that forms. You will have a saturated solution of each metal hydroxide with some white solid undissolved at the bottom of the test tube
3) Measure the pH of each solution - the alkalinity will increase down the group
Why are Group 2 compounds used as bases?
Due to their basic properties and ability to neutralise acids
Which Group 2 compound is used in agriculture?
Calcium hydroxide, Ca(OH)2
Why is calcium hydroxides added to fields?
To increase the pH of acidic soils - the calcium hydroxide neutralises acid in the soil, forming neutral water
What two Group 2 compounds are used in medicine?
Calcium carbonate and magnesium hydroxide
Why are calcium carbonate and magnesium used in medicine?
They are used as antacids for treating acid indigestion by neutralising hydrochloric acid in the stomach
