Group 2: Physical/ Chemical Properties Flashcards
Trend for atomic radius as you go down group from Mg- Ba. Explain.
- Atomic radius increases as you go down the group.
- More electron shells between the nucleus and the outer electron.
What are group 2 metals referred to as?
- Alkaline- earth metals.
How does the melting point change as you go down the group from Mg- Ba? Explain
- OVERALL, melting point decreases.
- Positive ions get bigger as you go down group, increased distance between positive nucleus/ sea of delocalised electrons means weaker force of attraction between positive nucleus/ sea of delocalised electrons.
- Less energy is required to break these forces.
What is the exception to the melting point decreasing as you go down the group from Mg- Ba? Briefly explain why this exception occurs…
- Exception = Mg.
- Mg melting point significantly less than others due to its structure (don’t need to know any more than that!)
() - extra info for clarification.
Trend in first ionisation energy as you go down group from Mg- Ba? Explain?
- First ionisation energy decreases.
- As you go down group, atom has more shielding/ outer electrons are further away from the nucleus.
-Two factors means: weaker force of attraction between positive nucleus/ outer electrons. - So, outer electron is lost more easily/ less energy needed to remove outer electron.
What block elements are group 2 metals?
- S block elements.
What type of bonding do these alkaline earth metals have?
- Metallic bonding.
How does barium react with water? Give balanced symbol equation (include state symbols.)
Which other group 2 elements react in this way with water?
Ba (s) + 2H₂O (l) –> Ba(OH)₂ (aq) + H₂ (g)
All group 2 elements react with water in this way other than magnesium.
How does magnesium react with water when it is in a liquid state vs a gas state (ie. steam?)
- Magnesium will react with cold water (liquid) very slowly.
- But, if magnesium reacts with steam, it will react a lot more quickly and form magnesium oxide (instead of hydroxide) and hydrogen.
Write balanced symbol equation for reaction of magnesium with steam?
Mg (s) + H₂O (g) –> MgO (s) + H₂ (g)
How do the solubility of group 2 metal sulphates and hydroxides change as you go down group?
- Sulphates (and any double-charged ions): as you go down the group, solubility of these compounds decreases.
- Hydroxide (singly charged ions): as you go down the group, solubility of these compounds increases.
How can you test for sulphate ions in an unknown solution?
- Add HCl to substance - to remove any carbonates in the solution.
- Then, add barium chloride to the substance.
- If sulphate ions exist in substance, a white precipitate of barium sulphate should be formed (because barium sulphate is insoluble.)
True or False
Barium sulphate is NOT VERY SOLUBLE in water.
- False.
- Barium sulphate is insoluble in water.
What is Mg(OH)₂ solubility like?
- Sparingly soluble (ie. has low solubility.)
() - extra info for clarification
What can group 2 compounds neutralise? Give specific examples?
- Group 2 compounds can neutralised acids.
- Ca(OH)₂ used in agriculture to neutralise acidic soils.
- Mg(OH)₂ neutralises excess stomach acid.
Use of BaSO₄?
- Used in “barium meal.” -identify problems in digestive tract.
- Patient takes barium sulphate. This coats the soft tissues in digestive tract.
- X- rays are absorbed by barium sulphate and will be seen on the image. (to show any blockages/ issues. normally X rays go straight through soft tissue.)
() - extra info for clarification
Why can BaSO₄ be taken in barium meal to outline the gut in X rays if Barium is toxic?
- Because BaSO₄ is insoluble so won’t be absorbed into the blood.
Why do we acidify the sample we are testing for sulphate ions?
- Acidifaction removes any carbonate ions (in solution ie. from water) that may lead to formation of white precipitate (ie. ensures formation of white precipitate is due to sulphate ions.)
Why does reactivity of group 2 elements with water increase as you go down the group?
- Atoms get larger –> outer electron is further away from the positive nucleus ALSO More shielding.Easier for the outer electron to be lost (weaker attraction between positive nucleus/ outer electron), so reactivity increases.
What substances do group 2 elements form when they react with water?
- Bases.
Steps in extraction of titanium from its ore.
- Titanium ore (TiO₂) is heated with carbon and chlorine gas, forming titanium (- 4- IV - chloride)
- Titanium 4 chloride is purified by fractional distillation.
- Purified TiCl₄ (titanium 4 chloride) is reduced using magnesium in a 1000⁰C furnace - forming pure Ti (titanium.)
What is titanium used in and why?
- Aircrafts.
- Because it is light yet strong.
Equation to show reaction between TiCl₄ and Mg
TiCl₄+ 2Mg –> Ti + 2MgCl₂
How can CaO or CaCO3 be used to remove sulphur dioxide from flue gases (when burning fossil fuels?)
- CaO or CaCO3 are dissolved in water and then sprayed on acidic sulphur dioxide gas.
- The CaO or CaCO3 (dissolved in water) neutralise the sulphur dioxide in flue gases.
