3.2.2 - Group 2, The Alkaline Earth Metals Flashcards
Group 2 elements lose __ electrons when they react
2
(all end s2 & make 2+ ions)
Atomic Radius _____ Down the Group
Increases
Why does atomic radius increase down the group? (3)
- Number of shells increase
- More distance between nucleus and outer electrons
- Outer shells more shielded
- Less attraction between nucleus and outer electrons
First Ionisation Energy ______ Down the Group
Decreases
Explain why first ionisation energy decreases down the group (4)
- Number of shells increase
- Increased distance between nucleus and outer electrons
- Outer shells more shielded
- Less attraction between nucleus and outer electrons
- Easier to remove outer electron = less energy
Reactivity ______ Down the Group
Increases
Explain why reactivity increases down the group
- First ionisation energy decreases down group
- Due to increasing atomic radius and shielding effect
- When Group 2 elements react = lose electrons & form positive ions
- Easier it is to lose electrons (i.e. the lower the 1st and 2nd ionisation energies) = more reactive the element
- So reactivity increases down group
Melting Points _______ _______ Down the Group
Generally Decrease
Describe Group 2 elements’ structure
- Metallic structures
- Positive ions in crystal structure surround by delocalised electrons from outer electron shells
Why do melting points generally decrease down the group? (4)
- Size of positive ion increases, but charge remains the same
- Delocalised electrons further away from positive ions
- Weaker electrostatic forces of attraction between positive ions and delocalised electrons
- Weaker metallic bonds = less energy needed to break
Where is there a big ‘blip’ at magnesium?
∵ crystal structure (arrangement of metallic ions) changes
Group 2 Elements React with ____
Water
When they react with water, they are oxidised from start of ____ to ____ forming ____ ____
When they react with water, they are oxidised from start of 0 to +2 forming M2+ ions
When Group 2 metal react with water, what 2 products do they give?
Metal hydroxide and hydrogen
Group 2 Elements React with Water
State the general symbol equation
Group 2 metals react ___ _____ down the group
more readily
Why do Group 2 metals react more readily down the group?
∵ ionisation energies decrease
Solubility Trends depend on ______ ___
Compound Anion
State the 2 general solubility trends of Group 2 elements
- Generally, compounds of Group 2 elements that contain singly charged negative ions (e.g. OH-) ↑ in solubility down group
- Compounds that contain doubly charged negative ions (e.g. SO4-2) ↓ in solubility down group
Fill in the gaps
What are compounds like magnesium hydroxide, which have very low solubilities said to be?
Sparingly soluble
Barium sulfate is _____ in water
insoluble
Describe the test for sulfate ions (SO42-)
- Add dilute hydrochloric acid and then barium chloride solution, BaCl2(aq)
- If white precipitate of barium sulfate forms = original compound contained sulfate
Test for sulfate ions
Why should you acidify the solution?
To get rid of any lurking sulfites or carbonates which will also produce a white precipitate
What are Group 2 compounds used for?
To neutralise acidity
Name 2 common examples of Group 2 compounds that are used to neutralise acidity
- Calcium hydroxide (slaked lime, Ca(OH)2)
- Magnesium hydroxide (Mg(OH)2)
What is calcium hydroxide used for?
In agriculture to neutralise acidic soils
What is magnesium hydroxide used for?
- Used in indigestion tablets as an antacid
- Substance which neutralises excess stomach acid
State the ionic equation for neutralisation, include the state symbols
(for both Ca(OH)2 & Mg(OH)2)
H+(aq) + OH-(aq) → H2O(l)
What is barium sulfate is used in?
‘Barium Meals’
Barium sulfate is ______ to X-rays
Barium sulfate is opaque to X-rays - won’t pass though it
What are ‘barium meals’ used to help?
Diagnose problems with oesophagus, stomach or intestines
Describe how ‘barium meals’ are used
- Patient swallows barium meal
- Barium sulfate coats tissues, making them show up on X-rays, showing structure of organs
What is magnesium used for?
To extract titanium from its ore
Describe how magnesium is used to extract titanium from its ore
- Main titanium ore (TiO2) is converted to titanium(IV) chloride (TiCl4) by heating it with carbon in steam of chlorine gas
- Titanium chloride is then purified by fractional distillation
- Then reduced by magnesium in furnace at 1000°C
Represent how magnesium is used to extract titanium from its ore by writing an equation
What is wet scrubbing?
When acidic sulfur dioxide is removed from flue gases by reacting with an alkali
Name 2 substances that can be used to remove sulfur dioxide from flue gases
Powdered calcium oxide (CaO, lime) and calcium carbonate (CaCO3, limestone)
Describe how calcium oxide and calcium carbonate is used to remove sulfur dioxide from flue gases
- Slurry is made by mixing calcium oxide or calcium carbonate with water
- The sprayed onto flue gases
- Sulfur dioxide reacts with alkaline slurry and produces solid waste product, calcium sulfite
Represent how calcium oxide is used to remove sulfur dioxide from flue gases by using an equation
Represent how calcium carbonate is used to remove sulfur dioxide from flue gases by using an equation
Explain why it’s possible to use barium sulfate in barium meals even though barium ions are poisonous
Barium sulfate is insoluble ∴ non-toxic
Explain why the electronegativity values of Group 2 elements Be-Ba decrease down the group (2)
- Increases in no. of shells/increased sheilding
- Decreased attraction for bonding electrons
Write the ionic equation, with state symbols, to show the reaction of calcium with an excess of water
Ca(s) + H2O(l) → Ca2+(aq) + 2OH-(aq) + H2(g)
Magnesium reacts rapidly with ___
steam
State two observations made when magnesium reacts with steam (2)
- White light
- White powder
Write the equation for when magnesium reacts with steam
Mg + H2O → MgO + H2
