Module 3.1.2 - Group 2 Flashcards
What is another name for group 2 elements?
Alkaline earth metals (all form hydroxides that are alkaline)
What is the electron configuration for group 2 elements?
All end in (shell no.)s2
What block elements are group 2 elements and why?
They are s-block elements
- their highest energy orbital occupies an s orbital
What structure do group 2 elements have?
giant, metallic structure
Why are group 2 elements good electrical conductors?
Have mobile delocalised electrons, which can move and carry charge
Why do group 2 elements have a high melting and boiling point?
- a lot of heat energy is required to break the strong metallic bonds
What happens when a group 2 element reacts?
A di-positive ion is formed, as the atom loses two electrons
What do group 2 elements undergo?
Oxidation
What happens to the atomic radii as you go down group 2 elements?
The atomic radii increases down group 2..
- there are more shells, more shielding effect by inner shell electrons
- increased distance of outer shell electron and increased shielding effect far outweigh the increase in nuclear charge
- nuclear attraction decreases on the outer shell electrons down group 2, so atomic radii increases
What happens to first ionisation energy as you go down group 2 elements?
First Ionisation energy decreases down group 2 as…
- atomic radius increases
- there are more shells, more shielding effect by inner shell electrons
- increased distance of outer shell electrons from nucleus and increased shielding effect far outweigh the increase in nuclear charge
- nuclear attraction on outer shell electron decreases
- less energy therefore needed to remove an electron from the outer shell of the atom
What happens to reactivity of group 2 elements as you go down?
Reactivity as you go down increases as..
- atomic radius increases
- there are more shells, more shielding effect by inner shell electrons
- increased distance of outer shell electrons from nucleus and increased shielding effect far outweigh the increase in nuclear charge
- weaker nuclear attraction on outer shell electrons
- ionisation energy decreases
- less energy is needed to remove 2 electrons from the outer shell of group 2 atom, hence reactivity increases
What happens in group 2 elements with oxygen?
- react vigorously with oxygen to produce an oxide (with ionic bonding)
- can be burned in air or an atmosphere of pure oxygen
What does a group 2 element and oxygen produce?
[Group 2] metal oxide (solid)
redox
What can identify the group 2 element of the metal oxide?
The colour of the flame in which the metal oxide is produced in
What is produce when group 2 elements reacts with water
- redox reaction
- react with cold water (room temperature)
[Group 2] Metal hydroxide (aq) + Hydrogen gas
What are metal hydroxides?
Weak bases (pH 10-12)
What is seen when group 2 elements react with water?
- solid disappears (dissolves)
- Bubbles of gas (fizzing - H2 evolved)
What happens down group 2 when reacting with water?
They react more vigorously down the group
What is the reaction between steam and magnesium?
Mg (s) + H2O (g) -> MgO(s) + H2(g)
What is formed when a group 2 element reacts with an acid?
[Group 2] Metal salt (aq) + hydrogen gas , redox
What is formed when group 2 oxides react with water?
- an alkaline solution of the metal hydroxide, not redox
metal oxide + water -> metal hydroxide
What is formed when group 2 hydroxides react with water?
- Group 2 hydroxides dissolve in water to form alkaline solutions
- Dissolve into its ions (M 2+, 2OH -)
What happens to the solubility of metal hydroxides down group 2?
Solubility of group 2 metal hydroxides increases down the group
What happens to alkalinity of group 2 hydroxides down the group?
Increases down the group
What happens to solubility of group 2 sulfates down the group?
Decreases
How is magnesium hydroxide used industrially?
- Used in indigestion tablets as an antacid
- Neutralises excess stomach acid safely
How is calcium hydroxide used industrially?
- Used in agriculture to neutralise acid soil
- reacts with acid substances in the soil
How is barium sulfate used in industry?
- Used in medicinal purposes for visualising X-rays
- insoluble in solution, does not release toxic barium ions into bloodstream
What is thermal decomposition?
The breaking up of a chemical substance with/by heat into at least two chemical substances
What are group 2 carbonates decomposed by heat into?
Solid metal oxide + Carbon dioxide gas
Why do group 2 carbonates become more difficult to decompose with heat as you more down the group?
The thermal stability of group 2 carbonates increases down the group
