Flashcards in 3.2.2 - Group 2: Alkaline Earth Metals Deck (24):
Group 2 metals _______ to ___ _____.
Group 2 metals oxidise to +2 ions.
Atomic radius _______ down group 2.
Atomic radius increases down group 2.
Reactivity _______ down group 2.
Reactivity increases down group 2.
First ionisation energies _______ down group 2.
First ionisation energies decrease down group 2.
What kind of bonding do group 2 elements undergo?
Metallic bonding - between +2 ions and a sea of delocalised ions
Bonding ______ in strength down the group. Why?
Decreases: atomic radii increase, but each metal atom still loses only two electrons (to form a +2 ion). This means that there is less attraction between the delocalised electrons and the positive ion nuclei.
There is a ______ charge density on the ions going down the group.
There is a lower charge density on the ions going down the group.
Exception of bpt trend down group 2? Why?
Magnesium: the bpt of magnesium is lower than that of calcium. This is because of magnesium's irregular crystal structure.
State the general equation for group 2 elements reacting with water. Water acts as an _______ ______.
M (s) + 2H2O (l) -> M(OH)2 (aq) + H2 (g)
Water acts as an oxidising agent.
State the equation for magnesium reacting with water vapour.
Mg (s) + H2O (g) -> MgO (s) + H2(g)
Magnesium reacts very quickly with cold water. True/false?
False - magnesium reacts very slowly with cold water, but very rapidly with steam.
Trend in the solubility of group 2 metal/hydroxide anion compounds down the group?
Solubility of metal hydroxide compounds increases down the group
Magnesium hydroxide is soluble. True/false?
False: magnesium hydroxide is sparingly soluble and is a solid suspension in water.
Ca(OH)2 is _______ soluble.
Use of calcium hydroxide?
Lime water solution! Also slaked lime and neutralises acidic soils.
Sr(OH)2 is insoluble. True/false?
False - Sr(OH)2 is soluble.
Ba(OH)2 dissolves to form what? State the equation.
A very alkaline solution: Ba(OH)2 (s) + aq -> Ba2+ (aq) + 2OH- (aq)
Trend in the solubility of group 2 metal/sulfate anion compounds down the group?
Solubility of metal sulfate compounds decreases down the group
Use of barium sulfate, BaSO4?
Barium meals - taken by patients with gastric problems, as it is opaque to x-rays so will absorb them and highlight blockages on an x-ray of the digestive system.
Is BaSO4 safe to take orally?
Yes - it is insoluble so does not enter the bloodstream.
Use and name for Mg(OH)2?
'Milk of magnesia': an antacid that treats heartburn.
What is the neutralisation equation?
H+ + OH- -> H2O
Test for sulfate ions, SO4^2-?
1. Add HCl or HNO3 (to react with and remove sulfites and carbonates that would form a false positive).
2. Add BaCl2.
3. Positive: white precipitate of BaSO4.