Here’s a clear comparison of the reactivity of Group 1 (alkali metals) and Group 2 (alkaline earth metals):
Group 1 (Alkali Metals)
- Very reactive metals.
- Reactivity increases down the group (Li < Na < K < Rb < Cs).
- They have 1 valence electron, which is easily lost to form a +1 cation.
- React vigorously with water to form metal hydroxides and hydrogen gas.
- Softer, lower melting points, and more reactive than Group 2 metals.
Group 2 (Alkaline Earth Metals)
- Reactive, but less reactive than Group 1 metals.
- Reactivity also increases down the group (Be < Mg < Ca < Sr < Ba).
- They have 2 valence electrons, so they need to lose two electrons to form a +2 cation, which requires more energy.
- React with water more slowly (Mg reacts only with steam, while Ca, Sr, Ba react more readily).
- Harder, higher melting points, and less reactive compared to Group 1 metals.
Key Comparison
- Group 1 > Group 2 in reactivity because:
- They lose only 1 electron (easier).
- Their ionization energy is lower.
- Their atoms are larger and the outer electron is more weakly held.
In short:
- Alkali metals (Group 1) are more reactive than alkaline earth metals (Group 2).
- Both increase in reactivity as you go down the group, but Group 1 always stays ahead.