1. Magnesium atoms also have a slightly smaller radius than sodium atoms, and so the delocalised electrons are closer to the nuclei.
2. Sodium has higher melting point than potassium because of stronger metallic bonding .
3. Potassium are very soft metal can be very easily cut with a knife
4. Increase of resistance in metals. Therefore the mobility of electrons decreases and causes decrease in conductivity.
5.To increase strength, increase corrosion resistance, or reduce costs.
6. All metals have low ionization energies and are relatively electropositive, and so they lose electrons fairly easily.
7. All the group 1 metals are reactive, but they get more reactive as you go down the group, so potassium is more reactive than sodium.