Topic 4A: Group 1 and 2 Flashcards
Define the first ionisation energy of an element
the energy needed to remove an electron from each atom in one mole of atoms in the gaseous state
Define the second ionisation of an element
the energy required to remove an electron from each singly charged postive ion in one mole of positive ions in the gaseous state
What is the general equation for first ionisation energy, using M?
M(g) —> M+(g) + e-
What is the general equation for second ionisation energy, using M?
M+(g) —> M2+(g) + e-
What is the trend of ionisation energies in Group 2?
decrease, as a result an increase in reactivity down the group
Name the factors to consider when explaining trends in ionisation energies
- the nuclear charge, or number of protons
- the obital in which the electron exists
- the shiedling effect
Give reasons why ionisation energy decreases down Group 2
- increased nuclear charge=force of attraction for the electron being removed increases
- as each quantum shell is added, energy of the outermost electron increases
- as the number of filled inner shells increases, their force of repulsion on the electron being removed increases, so a decrease in ionisation energy
- the effect of the last 2 factors outweighs the higher nuclear charge so ionisation energy decreases
What is the general equation for Group 2 metals and oxygen?
2M (s) + O2(g) —> 2MO (s)
What is the general equation for Group 2 metals and chlorine?
M(s) + Cl2(g) —> MCl2(s)
What observations would be made when Group 2 metals react with oxygen?
- very bright flame
- formation of a white solid
- barium = most reactive
What is the general equation for Group 2 metals and water?
M(s) + 2H2O(l) —> M(OH)2(aq) + H2(g)
What happens when calcium reacts with water?
Calcium hydroxide produced is only slightly soluble in water so is a solid not aqueous- the liquid in the experiment goes cloudy as a precipitate of calcium hydroxide forms
Give the equation for magnesium heated with steam
Mg(s) + H2O(g) —> MgO(s) + H2(g)
What are basic oxides?
oxides of metals that react with water to form metal hydroxides, and with acids to form salts and water
What’s the test for carbon dioxide?
limewater goes cloudy as a white precipatate froms
equation: CO2 + Ca(OH)2 —> CaCO3 + H2O
What is the trend in solubility for Group 2 hydroxides?
increases down the group
How do you neutralise hydrochloric acid in the stomach?
milk of magnesia (magnesium hydroxide solution)
equation: Mg(OH)2 + 2HCl –> MgCl2 + 2H2O
What is the products of Group 2 oxides and hydroxides with acids?
salt and water (neutralosation)
observation: white solid reacts to form colourless solution
What is the trend in solubility of Group 2 sulfates?
decreases down the group
magnesium sulfate is soluble
calcium sulfate is slightly soluble
strontium sulfate and barium are insoluble
How do you test for sulfate ions?
adding a solution containing barium ions to from a white barium sulfate precipitate e.g. dilute nitric/HCl acid and barium nitrate solution (H+ ions are present to prevent barium carbonate forming as a white precipitate)
Define thermal stability
a measure of the extent to which a compound decomposes when heated
Why is the thermal stability different for Group 1 and 2 nitrates and carbonates?
- the charge on a Group 2 cation is double Group 1
- the size and ionic radius of a Group 2 cation is smaller than a Group 1 cation
- the nitrate and carbonate ions are more complex than the Cl-
What happens when a Group 2 nitrate decomposes?
forms metal oxide, nitrogen dioxide gas and oxygen
What happens when a Group 2 carbonate decomposes?
the larger, complex ion changes into a smaller, more stable oxide ion (O2-) by decomposing and releasing carbon dioxide. forms metal oxide and carbon dioxide
