Group 2: the alkaline earth metals -2
- Created by: Shannon
- Created on: 26-03-15 10:31
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- Group 2: the alkaline earth metals
- Ionisation energies
- First ionisation energy
- The energy change when one mole of atoms of an element in a gaseous state loses on electron to form one mole of positive ion
- General trend
- Decreases down the group
- Progressively easier to remove an outer electron due to an increase in atomic radius
- More shielding from attraction of nucleus
- Progressively easier to remove an outer electron due to an increase in atomic radius
- Decreases down the group
- Second ionisation energy
- The energy change when one mole gaseously 1+ ions loses one mole of electrons to form one mole of 2+ ions.
- Third ionisation energy
- Trend
- Big increase in value for ionisation energy - removing electron from a subshell closer to the nucleus
- Trend
- First ionisation energy
- Reaction with oxygen
- Burn in oxygen to form solid metal oxides
- Reactivity increases down the group
- Reaction with chlorine
- Burn in chlorine gas to form solid metal chlorides
- Reactivity increases down the group
- Reaction with water
- React with water to form either oxides or hydroxides
- Reactivity increases down the group
- Magnesium - produces oxide Mg + H2O -> MgO + H2
- Ca, Sr & Ba produce hydroxides
- e.g Ca + H2O -> Ca(OH)2 + H2
- Reactions of group 2 oxides
- Water
- Mg reacts only slightly
- Ca, Sr & Ba react to form metal hydroxide
- Dilute acid
- Form metal chloride salt and water
- Water
- Reactions of group 2 hydroxides
- Dilute acid
- Form metal chloride salt and water
- Dilute acid
- Solubility
- Hydroxides
- Increases down the group
- Calcium hydroxide used in water treatment
- Sulfates
- Decreases down the group
- Barium sulfate used in xrays
- Hydroxides
- Flame colours
- Visible due to the movement of electrons
- Electrons gain energy, moving to higher orbitals
- Returning to ground state emits light energy
- Electrons gain energy, moving to higher orbitals
- Characteristic colours
- Li = Red
- K = lilac
- Ca = orange/red
- Cs = blue/violet
- Sr = brick red
- Ba = pale green
- Visible due to the movement of electrons
- Ionisation energies
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