We've been having few lessons and experiments at school that have to do with alkali metals. Those HUGE explosions (especially K and Cs) in reacting with water make you think about them. But there are a few things I can't figure out, and I'd appreciate any help possible in my following questions?

 

1. Why are alkali metals so reactive?

2. Why can't you touch Na with uncovered hand?

3.Why metallic sodium (Na) is soft and malleable, while NaCl is strong and frail?

 

I's REALLY appreciate some answers.

1/ that single electron in the outer shell is only weakly held because of sheilding effects from electrons in lower orbitals. it only 'sees' a fraction of the charge of the one excess proton.

 

2/you can touch Na with the uncovered hand, though if your sweaty then it will get quite warm. unless of course it is reffering to the layer of sodium hydroxide that would appear as a barrier. excluding that, you can even hold Rb in your bare hands as long as they don't sweat(or you wouldn't have any hands) i've done it though only for a few seconds as my hands were getting pretty warm by then.

 

3/metallic bonds are looser than ionic bonds.

alkali metals have low electronagetivity hence they can lose electrons easily. lithium can even force hydrogen to accept electrons. to my knowledge only alkali metals form stable binary hydrides . this is because thier outer most electron is not coupled,and is effectively shielded. you shouldn't touch Na because it keeps reacting with moisture in air and can react with the same on u'r skin(i have touched it its quite hot in air).nacl is hard because of strong electrostatic attraction while Na have mettalic one.

3/metallic bonds are looser than ionic bonds.

Thanks a lot insane_alien.

I was discussing with a friend of mine about metallic and ionic bonds and he started to get a little freaky about it. Sodium is malleable because of metallic bonds (thnx!), but this malleability causes only dislocation of structural nets, giving them the shape we want, but still these metallic bonds don't get "cut off", they still remain, right?

My friend is quiet sure that they break.

its iffy. a metal is effectively a bunch of positive ions in an electron gas(as the valence electrons are free to move everywhere withing the material, what makes it shiny and a good conductor) the bonds aren't the same as the conventional bonds so cannot really be said to break or form.

 

i'll go read up my metallurgy stuff and get back to you