Unit 2: Section 2- Group 2 and Group 7 Elements + RP4 Flashcards
What are group 2 known as?
The alkaline earth metals
How many electrons do group 2 elements have in their outer shell?
2
Name three trends that happen as you go down group 2
- Increasing atomic radius
- Decreasing first ionization energy
- Decreasing melting points
Explain the change in atomic radius as you go down group 2
Atomic radius increases as you go down group 2, as the number of shells increases by one as you go down group 2. This increases the distance and shielding between the outer electrons and the nucleus, decreasing the electrostatic attraction between them.
Explain the change in first ionization energy going down group 2
First ionization energy decreases down the group because the outermost electrons are further away from the nucleus, so less energy required for an electron to be removed. There is also an increase in shielding down the group, which decreases the attraction of the outer electron to the nucleus
Explain the change in melting point down group 2
Melting point decreases down the group because the metallic bonds become weaker as the size of the atoms increase. The greater the distance between the delocalized electrons and positive ions, the weaker the electrostatic forces of attraction
What forms when you react a group 2 metal with oxygen?
it forms a metal oxide
What is the general equation for group 2 metals reacting with oxygen?
2M + O2 –> 2MO
What is a useful property of magnesium?
It is very easy to ignite
What flame does magnesium burn with?
bright white flame
What happens when magnesium is ignited?
bright white flame
formation of a white powder
What happens to the magnesium when it is oxidized without being ignited?
Without a flame this reaction happens very slowly. The MgO in this case is formed as a thin layer that covers the surface of the magnesium.
What must happen to Mg if a thin layer of MgO has formed if the metal is to be used in electrolysis?
It must be rubbed down with emery paper to remove this oxide layer.
How does most of group 2 react with water?
very vigorously
What is the general equation for group 2 metals reacting with water?
M + H2O –> M(OH)2 + H2
forms metal hydroxide and hydrogen gas
What happens to metal hydroxides that are soluble?
They stay in solution, so an alkaline aqueous solution is formed in the reaction
How reactive is magnesium compared to the rest of group 2?
Magnesium is the least reactive of the group 2 metals
What is the only thing that magnesium will react with?
Magnesium will only react with warm water
What is the chemical reaction with Mg and warm water, also describe it
Mg (s) + 2H2O (l) –> Mg(OH)2 (aq) + H2 (g)
- tame reaction
- doesn’t produce a flame
What happens if magnesium reacts with steam?
If magnesium reacts with steam, it forms magnesium oxide and hydrogen.
This reaction does produce a flame, with magnesium burning with a bright white colour:
What is the only element in group 2 that does not react with water?
Beryllium
What observations could you observe from reactions of group 2 metals with water? (6)
- increase in temp
- metal dissolving
- melting of the metal into a ball
- metal moving around surface of water
- ignition of the metal, burning with a colored flame
- effervescence (hydrogen gas)
What happens to the reactivity of the metals as you go down group 2?
it increases
As the metals become more reactive, the reactions become more explosive.
How can titanium be extracted?
It can be extracted from its ores using the Group 2 metal magnesium
Name some uses/properties of titanium (2+3)
- used in aircrafts and
- in hip replacements
for its resistance to
- corrosion,
- abundance
- low density.
Why is titanium so expensive? (4)
- high temperatures are needed in the extraction
- The extraction process also requires an argon environment which is expensive.
- Magnesium is also required for extraction, which is expensive
- Extracting titanium is a batch process, which means that a lot of labour is required and energy is lost whenever the process stops.
Why cant titanium be extracted using carbon?
It would lead to the production of titanium carbide instead of titanium metal.
Why cant titanium be extracted via electrolysis?
It is not reactive enough
List the three steps of extracting titanium using magnesium
- solid titanium oxide is converted to liquid titanium chloride
- the liquid titanium chloride is then purified by fractional distillation
- magnesium is added to the liquid titanium chloride to extract solid titanium. As magnesium is more reactive than titanium, it will displace it in the salt to form magnesium chloride
What temperature is solid titanium chloride converted to liquid titanium chloride at and why?
9000 C
Done for purification as TiCl4 is liquid at room temperature
What is the reaction for the extraction of titanium using magnesium?
TiCl4 (l) + 2Mg (s) → Ti (s) + 2MgCl2 (l)
What do group 2 metals form when reacting with water?
Metal hydroxides
What happens to solubility as you go down group 2?
solubility increases
Why does solubility increase as you go down group 2?
Because there is an increasing radius of the metal cations
How does ions being similar in size effect electrostatic attraction?
Ions that are similar in size will experience stronger electrostatic attractions to one another as they are able to get closer together
Why does the metal cation being small effect the solubility of hydroxides ionic compounds?
As the hydroxide ion is quite small, smaller metal cations will create stronger, and so less soluble ionic compounds.
What happens if you dissolve a group 2 metal in solution?
when dissolved in solution they will form alkaline solutions, with the alkalinity of the solutions increasing down the group as solubility increases
Why is magnesium hydroxide considered to be ‘sparingly’ soluble?
Though magnesium hydroxide is considered insoluble in water, in a solution of magnesium hydroxide and water, the solution will become slightly alkaline. This solution will be about pH 9, meaning that some hydroxide ions are present.
Describe how magnesium hydroxides can be used in medications
Magnesium hydroxides lack of solubility makes it ideal for use in anti-acid medications. Usually taken in the form of a chewable tablet, Mg(OH) reaches the stomach as a solid, where upon it neutralizes with excess stomach acid.
What pH solution does calcium hydroxide produce with water?
Calcium hydroxide is partially soluble in water, producing an alkaline solution (pH 11).
What is another name for limewater?
aqueous calcium hydroxide
What can be used to test for carbon dioxide?
limewater
What happens in a positive test for carbon dioxide?
Aqueous solutions of calcium hydroxide (limewater) can be used to test for carbon dioxide. In this test, CO2 is bubbled through limewater causing calcium carbonate to be formed which presents as a white precipitate
What is the equation for a positive test for carbon dioxide?
Ca(OH)2 (aq) + CO2 (g) →CaCO3 (s) + H2O (l)
What is calcium carbonate used in the removal of?
used in the the removal of sulfur dioxide from flue gasses.
A slurry of CaCO3 is sprayed into the gasses and reacts reacts with acidic sulfur dioxide to produce solid calcium sulfite.
What can calcium hydroxide be used for?
Calcium hydroxide is also used in agriculture to maintain soil quality. When soil becomes too acidic for a crop, Ca(OH)2 can be added to increase its pH
What is barium hydroxides solubility in water?
barium hydroxide is very soluble in water. this means that a solution of barium hydroxide and water is very strongly alkaline
What do the group 2 metals form when they are reacted with sulfuric acids?
metal sulfates
What trend does the solubility of group 2 metal sulfates follow in comparison to metal hydroxides?
hydroxides increase in solubilty
sulfates decrease in solubility
Why are the metal sulfates more soluble than the metal hydroxides in group 2?
because the sulfate ion is larger, and larger cations form stronger ionic compounds
How can barium sulfate be used?
in medicine, can be used as a contrast medium in certain types of X-ray due to its insoluble nature
can be used to allocate blockages in the digestive system
How can barium be used to test for sulfate ions in solution?
The insolubility of BaSO4 means that barium can also be used to test for sulfate ions in solution.
When barium chloride is added to a solution containing sulfate ions, the chloride ions will be displaced by the sulfate ions.
produces solid insoluble barium sulfate, which falls to the bottom of the reaction as a white precipitate.
Why does barium react slowly with sulfuric acid?
Barium reacts slowly with sulfuric acid because solid barium sulfate forms on the surface of the barium metal, slowing down the reaction
What states are fluorine, chlorine, bromine and iodine at room temperature?
gas
gas
liquid
solid
What color is fluorine, chlorine, bromine and iodine at room temperature?
pale yellow,
pale green,
dark orange liquid OR orange vapor
grey solid, purple vapor
What is the trend in electronegativity down group 7?
Electronegativity decreases down the group.
Why does electronegativity decrease down group 7?
because the atomic radii of the elements increase down the group, so the attraction between the nucleus and outer electrons decreases.
