EL - Group 2 Flashcards
What do group 2 elements react with?
Water and oxygen.
When group 2 elements react, what charge ions do they form?
2+
When group 2 metals react with water, what do they produce?
Hydroxides and hydrogen.
What do group 2 elements burn in oxygen to produce?
Solid white oxides.
What is the trend in reactivity of group 2 metals?
They get increasingly reactive down the group because the outermost electrons are further from the nucleus, and so more easily lost.
Why do the group 2 metals get more reactive as you go down the group?
They get increasingly reactive down the group because the outermost electrons are further from the nucleus, and so more easily lost.
What are group 2 oxides and hydroxides?
Bases.
Because group 2 oxides and hydroxides are bases, what does this mean they do?
Form alkaline solutions in water.
Neutralise acids.
Why do group 2 oxides and hydroxides form alkaline solutions in water?
The oxides of group 2 metals react readily with water to form metal hydroxides, which dissolve. The hydroxide ions, OH-, make the these solutions strongly alkaline.
How do group 2 oxides and hydroxides neutralise acids?
Because they’re bases both the oxides and hydroxides neutralise dilute acids, forming solutions of the corresponding salts.
Which group 2 metal oxide doesn’t form an alkaline solution in water and why?
Magnesium oxide because it only reacts slowly and the hydroxide isn’t very soluble.
How does the strength of the alkaline solutions formed by group 2 metal oxides and hydroxides change as you go down the group and why?
The oxides form more strongly alkaline solutions as you go down the group because the hydroxides get more soluble.
What pH does calcium hydroxide have?
12
What do the solubility trends of group 2 elements depend on?
The compound anion.
How does solubility of compounds of group 2 elements that contain singly charged negative ions change as you go down the group?
Increase in solubility as you go down the group.
How does solubility of compounds of group 2 elements that contain doubly charged negative ions change as you go down the group?
Decrease in solubility as you go down the group.
Rank these from least to most soluble: Calcium Hydroxide Strontium Hydroxide Magnesium Hydroxide Barium Hydroxide
LEAST: Magnesium Hydroxide Calcium Hydroxide Strontium Hydroxide Barium Hydroxide MOST:
Rank these from least to most soluble: Calcium Carbonate Strontium Carbonate Magnesium Carbonate Barium Carbonate
LEAST: Barium Carbonate Strontium Carbonate Calcium Carbonate Magnesium Carbonate MOST:
What are group 2 compounds like magnesium hydroxide, which have very low solubilities, said to be?
Sparingly soluble.
What do group 2 carbonates decompose to form?
Carbon dioxide and metal oxide.
When do group 2 carbonates form carbon dioxide and a metal oxide?
When they decompose.
What is thermal decomposition?
When a substance breaks down (decomposes) when heated.
How does the volume of carbon dioxide produced during decomposition of group 2 carbonates change as you go down the group?
Volume decreases as you go down the group as the Mr of the metal gets bigger, so a smaller number of metal carbonate moles is contained on the same mass.
Finish the statement:
The more thermally stable a substance is…
…the more heat it will take to break down.
How does thermal stability change as you go down group 2?
Increases down the group.
What type of ion are carbonate ions?
Large anions.
How can carbonate ions be made unstable?
By the presence of a cation such as a group 2 metal ion.
What does the presence of a cation do to a carbonate ion?
Makes it unstable.
How can a cation make large anions unstable?
The cation draws the electrons on the carbonate ion towards itself (it polarises it). This distorts the carbonate ion.
Finish the statement regarding cations making anions unstable:
The greater the distortion…
… the less stable the carbonate ion.
What charge do anions have?
negative
What charge do cations have?
positive
Which cause less distortion, large cations or small cations?
Large cations.
Why do large cations cause less distortion than small cations?
Because they have a lower charge density.
What is charge density?
The charge on the ion relative to its volume.
Explain the trend in distortion and stability that occurs as you go down group 2:
Further down the group, the larger the cations, the less distortion caused and the more stable the carbonate anion.
Which is less stable and why, magnesium carbonate or barium carbonate?
Magnesium ions polarise carbonate ions more than barium ions do, meaning magnesium carbonate is less stable.
How does charge density change as you go down group 2?
Decreases down the group.
