Why Do Elements Like Sodium And Potassium React So Vigorously? | And Why Are They So Soft?

We have seen a lot of alkalis react with water and some even with air as well. Like- Potassium And Sodium.

We even know what alkalis are, and in case, you don't, then no problem. Basically, alkalis are elements that are present below Hydrogen (H) in the periodic table.

The alkalis are - Lithium, Sodium, Potassium, Rubidium, Caesium And Francium.

This must arise 2 questions in your mind.

1) Why isn't Hydrogen an alkali?

Ans. First of all, hydrogen is not even a metal. Second, it does have one electron in its first shell. But the attraction of the nucleus to the electron is so much that its ionization energy is so high. And elements react when they either gain or loose electrons easily. In this case for hydrogen, it isn't possible to make it react so easily. So, that's why hydrogen isn't an alkali metal.

2) Calcium do reacts with water as well, then why it isn't an alkali?

Ans. Calcium is an alkali earth metal which is present in the class/group II-A of the periodic table, that is, calcium is present in the table group just next to the alkali metals. So, calcium is an alkali, but more precisely, an alkali earth metal.

So, coming back, why do elements like sodium and potassium react so vigorously?

As you can see, in the image, the last number of the K, L, M and N electronic configuration of these alkali is 1, which shows that they have only 1 valence electron.

It is very simple. What do alkali have in common? They have 1 valence electron. This means that the ionization energy required for it to become an ion is very less. We can easily kick out the electron from its valence shell. 

And because of this ability, alkalis like potassium are a lot more reactive than alkali earth such as calcium has 2 electrons in its valence shell, so it does requires a little not much but a little ionization energy to make it an ion, that's why calcium reacts slowly, but not vigorously.

So, when we add sodium to water, the sodium reacts with water molecules, and gives away its electrons as water provides sufficient energy for sodium so that it can get rid of it's last electron and become an ion or be, kind of stable. Same goes with other alkali.

Fact Time: Have you ever wondered a common thing in alkalis? It's their strength. If we take safe alkalis, and cut them, it would feel like cutting a soap! Yes, alkalis are soft, shiny metals.

Now, you may ask, why are they so weak to cut, as the title says. Well, the same reason as to why they react so vigorously. They have one valence electron its outer shell, that's why metallic bonding becomes very weak within the atom and between other atoms. Due to this, they have a very weak bonding of atoms in their crystal lattice or ocean of atoms in one sense. And that's why they are very weak at the surface level and it is very easy to cut these stuff out.

So, I have answered 2 questions a curious mind would have and I hope this helps you.

Thanks for reading. We are coming very soon with other great topics in science.