Elements in group 1 & 2 Inorganic chemistry

Define ionisation energy STARTER Define ionisation energy What is the trend for ionisation energy as we go down the group? Explain this trend.

Answers Energy required to remove an electron from a gaseous atom or ion As you move down a group, ionization energy decreases. More shielding, electrons are further from the nucleus and thus easier to remove the outermost one.

LO; Investigating group 2 metals Success criteria Understand the chemical properties of group 2 metals (LD) Explain the reaction between water and group 2 metals using equations (MD) Explain the trend of reactivity when group 2 elements react with oxygen or water (HD)

Group 2 Chemical Properties Physical Properties Solubility

Group 2 elements Group 2 Be Group 2 elements can react with water, oxygen & chlorine. When group 2 elements react they form ions with 2+ charges. This is because they lose the two electrons on their outer shell. You will need to know how to write the equations for all these reactions. Group 2 Be Mg Ca Sr Ba

Challenge; use state symbols Write me and equation for any group 2 metal with water? What do you think the products are? Challenge; use state symbols

Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g) Reaction with water When group 2 metals react with water they form a Metal hydroxide & Hydrogen oxidation states Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g) +1 +2 Sr is Oxidized – The Ox state goes from 0 to +2 – Loses Electrons Hydrogen is Reduced – The Ox state goes from +1 to 0 – Gains Electrons

Reaction with Water Be Doesn’t react Mg Reacts very slowly Ca Steadily Sr Fairly Quickly Ba Rapidly Reactivity increases as we go down the group

Explain the trend in reactivity The reactivity for the group 2 metals increases as we go DOWN the group Because it is easier to remove the electrons for 2+ charge Shielding increases as we go down the group Less nuclear attraction between the outer electrons and the nucleus

FLAME TESTs

Flame Tests Li Red Na Orange/Yellow K Lilac Ca Brick-red Rb Sr Crimson When group 1 or group 2 metals are burned in oxygen, coloured flames are produced. Li Red Na Orange/Yellow K Lilac Ca Brick-red Rb Sr Crimson Cs Blue Ba Green

Reaction with oxygen When group 2 metals react with oxygen, you get a solid white oxide 2Mg(s) + O2(g) ® 2MgO(s) oxidation states +2 -2 Mg is Oxidized – The Ox state goes from 0 to +2 – Loses Electrons Oxygen is Reduced – The Ox state goes from 0 to -2 – Gains Electrons

Reaction with CHLORINE When group 2 metals react with chlorine, they form metal chloride Ca(s) + Cl2(g) ® CaCl2(s) oxidation states +2 -1 Ca is Oxidized – The Ox state goes from 0 to +2 – Loses Electrons Chlorine is Oxidized – The Ox state goes from 0 to -1 – Loses Electrons

Plenary Which is the least reactive metal in Group 2? Why does reactivity with water increase down Group 2? Barium can be burned in chlorine gas. Write an equation for the reaction, including state symbols. Plenary