Group 2 Flashcards
What type of elements are in group 2
Metals known as the alkaline earth metals
What happens to atomic radius down the group
increases as one goes down a group the atoms have more shells of electrons making the atom bigger
what is the electronic structure of group 2 metals
all have outer shell S2 electron configuration
what happens to melting points down the group
decreases. Metallic bonding weakens as the atomic size the increases. The distance between the positive ions and the delocalised electrons increases. therefore the electrostatic forces between positive ion and the delocalised electron weaken
what happens to ionisation energy in group 2
when group 2 metal reacts they lose their outer shell s2 electrons in redox reactions to form 2+ ions.The energy to remove these electrons are first and second ionisation energies
what happens to the first and second ionisation energies down a group
the outermost electrons are held more weakly because they are successively further from the nucleus in additional shells
In addition the outer shell electrons become more shielded from the attraction of nucleus by the repulsive force of inner shell electrons.
how does the reactivity of group 2 metals increase
down the group
why does the reactivity increase down the group
As the atomic radius increases theres more shielding the nuclear attraction decreases and it is easier to remove outer electrons. Cations form more easily
whats the redox reaction with oxygen
group 2 elements all react with oxygen to form metal oxide made up of M2+ and O2+ ions
2Mg + O2 —–> 2MgO
MgO is a white solid with high melting point due to its ionic bonding
Redox reactions with water
Group 2 elements react with water to form an alkaline hydroxide with genral formula M(OH)2 and hydrogen gas
burn with big white flame
what happens when other group 2 metals instead of Mg react with cold water
will react with cold water with intense vigour produces hydroxides
what would you observe during the reaction with cold water
fizzing
metal dissolving (faster down the group)
solution heating up ( more down the group)
and with calcium a white precipitate ( less precipitate down the group)
Redox reaction with dilute acids
many metals take part in redox reactions with dilute acids to form a salt and hydrogen gas
metal + acid —> salt and hydrogen
what happens when barium metal is reacted with sulfuric acid
it will only react slowly as the insoluble barium sulphate produced will cover the surface of the metal and act as a barrier to further attack.
Same effect will happen to a lesser extent with metals going up the group as the solubility increases
same effect doesnt happen with other acids like hydrochloric or nitric as they form soluble group 2 salts
reactions of Group 2 oxides with water
oxides of group 2 elements react with water releasing hydroxide ions OH- and forming alkaline solutions of the metal hydroxide
CaO(s) + H2O (l) ——> Ca2+ (aq) + 2OH - (aq)
Are group hydroxides soluble in water
they are only slightly soluble in water. When the solution becomes saturated , any further metal and hydroxide ions will form a precipitate
what happens to the solubilty of the hydroxides in water down the group
increases down the group so the resulting solution contain more OH- (aq) ions are more alkaline
How can you show this solubilty trend
1)Add a spatula of each group 2 oxide in water in a test tube
2)Shake the mixture. 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 be seen to increase down the group
how are group 2 compounds used in agriculture
Calcium hydroxide is added to field as lime to increase the Ph of soils
