Chapter 9 (Group 2) Flashcards
What are group 2 elements also known as and why?
Alkaline earth metals because their oxides and hydroxides are alkaline.
How many electrons do they have in their outer shell?
2
Which orbital are the outer electrons in?
s-orbital
How does the radius of the atom change going down the group and why?
The atoms gets bigger as the atomic radius increases as there is an extra outer shell.
How does the melting point change going down the group?
The melting point decreases as the delocalised ‘ sea’ of electrons is further away from the positive nucleus. This means that the strength of the metallic bond decreases and the electrostatic attractive forces between positive ions and delocalised electrons weaken.
How does the ionisation energy change going down the group?
The ionisation energy decreases going down the group as the outer shell of the element become further away from the positive nucleus and the nucleus is shielded by more inner shells of electrons.
Why are all reactions for group 2 oxidation?
The elements lose both the electrons in their outer shell and go from oxidation state of 0 to oxidation state of 2+.
How does the reactivity with water change going down the group and why?
The elements become more reactive going down the group as there is more shielding between the positive nucleus and negative electrons in the outer shell so there is weaker attraction.
How do hydroxides appear?
They are white solids
How does the solubility of hydroxides change down the group?
They become more soluble down the group.
What is the use of barium sulphate?
As barium sulphate is insoluble, it can be ingested to show digestive organs on x-rays.
What is calcium hydroxide also known as and what is its use?
It is limewater and can be used to test for carbon dioxide and to get the correct pH for growing crops.
What is produced when a group 2 metal is reacted with STEAM?
Metal OXIDE and hydrogen
e.g. Mg (s) + H2O (g) > MgO (s) + H2 (g)
What is produced when a group 2 metal is reacted with WATER?
Metal HYDROXIDE and hydrogen
e.g. Mg + 2 H2O > Mg(OH)2 + H2
Which group 2 metal reacts with warm water?
Magnesium
Which group 2 metals react with cold water?
Calcium, strontium, barium
What are the observations from adding a group 2 metal to water?
- Fizzing, (more vigorous down group)
- The metal dissolving, (faster down group)
- The solution heating up (more down group)
- With calcium a white precipitate appearing (less precipitate forms down group with other metals)
What is the use for barium chloride?
Used to test for sulphate ions - white precipitate forms if sulphate is present.
Describe the process of using magnesium to extract titanium
1) TiO2 (s) is converted to TiCl4 (l) at 900 degrees c.
2) The TiCl4 is purified by fractional distillation in an argon atmosphere.
3) The Ti is extorted by Mg in an argon atmosphere at 500 degrees C.
Why is TiO2 converted to TiCl4?
Can be purified by fractional distillation as TiCl4 is molecular and solid at room temperature while TiO2 is ionic and solid at room temperature.
Why can titanium not be extracted by carbon or electrolysis?
Forms carbonise (TiC)
Cannot be extracted baby electrolysis as it has to be very pure.
Why is titanium expensive?
- Expensive cost of magnesium
- Batch process so is slower and requires more labour and energy is lost when the reactor cools down after stopping.
- Use of argon and need to remove moisture (TiCl4 is susceptible to hydrolysis)
- High temperatures required in both steps.
List hydroxides from most to least soluble
Barium Hydroxide - easily dissolvable
Calcium Hydroxide - partially soluble
Magnesium Hydroxide - insoluble
How does the solubility of sulphates change down the group?
Less soluble down the group
How would the full equation for formation of a sulphate precipitate be written?
XCl2(aq) + Na2SO4 > 2NaCl + XSO4
How would the ionic equation for the formation of a sulphate precipitate be written?
X^2+(aq) + SO4^2-(aq )> XSO4 (s)
How is a sulphate tested for?
Add Hydrochloric acid and white precipitate should form
How would insoluble salt be removed from a solution?
Filtration
Wash with distilled water to remove soluble impurities and then dry on filter paper.
What are spectator ions?
Do not change state or oxidation number
