Question

Sodium is more reactive than lithium, despite both belonging to group 1. Explain why

Answer 1

Na has more valence electrons than Li

It means Na has greater size  

which means it has weak forces of Attraction

And it is more easy to remove electron from Sodium than Lithium{has less electron than Sodium}

Hence,

Sodium is More Reactive than Lithium

Sodium has less Electro-negativity  than   Lithium

And Hence there is More Ionizing Energy Required to remove from Lithium than Sodium

Answer 2

In group 1, elements get more reactive going down the group. Sodium is more reactive than lithium since when going down, each element gains an extra valence electron, and the outer shell electrons get further and further away from the nucleus while also becoming more in number. Due to this, the element becomes unstable and more reactive.