3.1.2: Group 2 Flashcards
Group 2 elements form…
White or colourless (ionic) compounds
Group 2 elements are _____ conductors of electricity
good
Group 2 elements have oxidation number ___ in compounds§
+2
React with acids to give
Salt + hydrogen
Compared to Group 1 elements, Group 2 elements:
- Harder
- Higher MBP
- Stronger metallic bonding
Group 2 elements are called alkaline earth metals because
metal oxides and hydroxides are basic.
Explain the trends in the melting points of Group 1 and 2 elements
• Melting points decrease down Groups 1 and 2 ∵ larger atomic radii means charge density decreases down group
• Group 2 elements’ melting points are higher than those of Group 1
∵ Group 2 elements delocalise 2 electrons
∴ lots more energy needed to separate ions and delocalised electrons
• Higher charge density means higher melting point as more energy required to separate ions
Explain the trend in reactivity down Group 2
- Reactivity increases down group ∵ Ionisation energy decreases
- IE decreases ∵ atomic radius increases, so outermost e- further from nucleus, and there is more shielding (because more shells of electrons between nucleus and outermost electron)
- Increasing atomic radius and shielding outweigh increasing nuclear charge ∴ less energy required to remove outermost electron, hence reactivity increases down group
Hydroxides pH
11-14
Explain the trend in decomposition temperature of Group 2 carbonates
- Decomposition temperature increases with the size of the metal cation (i.e. atomic number)
- Decomposition harder (i.e. temp increases)
- Thermal stability of Group 2 carbonates increases down the Group
- Metal cation needs to polarise CO₃²⁻ ion to remove an oxygen to leave CO₂
- At the top of the group the metal ion is more charge dense ∴ can better take the O from CO₃ to leave CO₂
