Group 2, the alkaline earth metals Flashcards
Describe how the atomic radius changes down group 2.
Atomic radius increases down the group. As one goes down the group, the atoms have more
shells of electrons making the atom bigger.
Describe how the melting point changes down group 2.
Melting points decrease down the group. The metallic
bonding weakens as the atomic size increases. The
distance between the positive ions and delocalized
electrons increases. Therefore the electrostatic
attractive forces between the positive ions and the
delocalized electrons weaken.
Describe how the 1st ionisation energy changes down group 2.
Increased shells and increased shielding therefore less electrostatic between the nucleus and outer electron so it’s easier to lose.
Reactivity in Group 2.
Reactivity of group 2 metals increases down the group
The general equation for when G2 metals react with water.
Metal + Water ——–> Metal hydroxide + Hydrogen
State the equation and observations for the reaction between Mg and steam.
Mg (s) + H2O (g) —–> MgO (s) + H2 (g)
The Mg would burn with a bright white flame.
State the equation and observations for the reaction between Mg and warm water.
Mg + 2 H2O ——> Mg(OH)2 + H2
No reaction with cold water
White solid formed, fizzing
State the equation and observations for the reaction between Ca and cold water.
Ca + 2 H2O (l) ——> Ca(OH)2(aq) + H2(g)
Fizzing, white solid forming and slightly soluble.
General observations of reactions down group 2.
Fizzing, (more vigorous down group)
The metal dissolving, (faster down group)
The solution heating up (more down group)
With calcium, a white precipitate appearing
(less precipitate forms down the group with
other metals)
State the equation and observations for the reaction between Sr and cold water.
Sr + 2 H2O (l) ——> Sr(OH)2(aq) + H2(g)
Fizzing, colourless solution formed
State the equation and observations for the reaction between Ba and cold water.
Ba + 2 H2O (l) ——-> Ba(OH)2(aq) + H2(g)
Fizzing, colourless solution formed.
Steps in extracting titanium:
- TiO2 (solid) is converted to TiCl4 (liquid) at 900C.
- The TiCl4 is purified by fractional distillation in an argon atmosphere.
- The Ti is extracted by Mg in an argon atmosphere at 500C.
- TiO2 is converted to TiCl4 as it can be purified by fractional distillation, TiCl4 being molecular
(liquid at room temperature) rather than ionic like TiO2 (solid at room temperature).
Why can’t Titanium be extracted with Carbon?
Titanium cannot be extracted with carbon because titanium carbide (TiC) is formed rather
than titanium.
Titanium cannot be extracted by electrolysis as it has to be very pure.
Why is titanium expensive?
- The expensive cost of the Mg
- This is a batch process which makes it expensive because the process is slower (having to fill up and empty reactors takes time) and requires more labour and the energy is lost when the reactor is cooled down after stopping
- The process is also expensive due to the argon, and the need to remove moisture (because TiCl4
is susceptible to hydrolysis). - High temperatures required in both steps
Uses of titanium.
Titanium is a very useful metal because it is abundant, has a low density and is corrosion resistant – it is used for making strong, light alloys for use in aircraft.
