Group 2 Flashcards
What are group 2 elements sometimes called?
-alkaline earth metals
Why are group 2 metals called alkaline earth metals?
-due to the alkaline properties of the metal hydroxides that they form
what type of elements are group 2 elements?
-They are reactive metals and do not occur in the elemental form naturally
-It is the compounds that are most useful in manufacturing and industry
why does beryllium behave differently to the rest of the group 2?
due to its small size
how can group 2 hydroxides be prepared?
by the reaction of the metal oxide with water to form the group 2 hydroxide (e.g. SR (s) + H2O (l) —> Sr(OH)2 (aq)
What is the solubility of group 2 hydroxides in water?
They are only slightly soluble in water
what happens when a group 2 hydroxides dissolve?
they dissociate to release the metal cation and hydroxide OH- ions e.g. Ca(OH) (s) + aq —> Ca2+ (aq)+ 2OH- (aq)
what happens to the solubility of the hydroxides down the group and what does this mean?
solubility increases, therefore the resulting solution contains more/less OH- ions and is more/less alkaline
what pH values will these hydroxide solutions have?
-PH values, ranging from eight at the least soluble end to 14 at the bottom of the group
what happens as you go down group 2 hydroxides?
-Solubility increases
-PH increases
-Alkalinity increases
what is the use of Ca(OH)2?
agriculture because it neutralises acidic soils
What is the use of Mg(OH)2 and CaCO3?
-milk of magnesia to treat indigestion as it neutralises excess system stomach acid (HCl)
what are the uses of group 2 oxides, hydroxides, and carbonates related to?
their basic properties and ability to neutralise acids
what is the use of BaSO4?
Diagnostic medicine
What is the use of CaCO3?
construction/sculptures etc
why do group 2 metals have reasonably high melting and boiling points?
Due to having strong metallic bonds in their giant metallic lattice structures
why can group 2 metals conduct electricity in both solid and liquid (molten) phases?
Because the highest energy electron is found in an s-subshell
why do reactions in group 2 elements occur?
Due to their ability to lose two electrons from their outer shell
What do elements undergo when they lose electrons?
Oxidation
What do group 2 atoms therefore act as?
Reducing agents
as we descend group 2, what happens to the first and second ionisation energies?
The first and second ionisation energies decrease
Why do the first and second ionisation energies decrease as we descend group 2?
-The number of shells increases/radius increases
-shielding increases
-Nuclear attraction decreases (despite an increase in nuclear charge/ number of protons)
-Easier to lose an electron less energy is needed to remove the electrons
what would you expect to observe in the reaction between group 2 metals (e.g.barium) with water to form an alkaline hydroxide?
-effervescence
-Solid dissolves
-Colourless solution forms
what would be different about the resulting solution if you were to react calcium with water rather than barium?
The pH of the solution would be lower as calcium hydroxide is less soluble in water than barium hydroxide so less hydroxide ions would be dissociated into the solution
what is the reaction of magnesium with water?
-It is very slow- it reacts more vigourously with steam
-However the magnesium hydroxide produced decomposes to form magnesium oxide
what are the salts of the group 2 metals?
White crystalline compounds
how can the salts of group 2 metals be prepared?
by reacting the metal, metal oxide or metal carbonate with the appropriate acid
If magnesium is reacted with sulphuric acid, rather than strontium, what differences would you observe as the reaction took place?
-solid would dissolve slower
-It would bubble less vigourously
what is the trend in the reactivity of group 2 metals with dilute nitric acid?
-reactivity increases as- the electron is further away from the nucleus, atomic radius, shielding increases the number of shells increases, so nuclear attraction decreases
-This causes ionisation energy to decrease, so it’s easier to lose electrons
