IONIC COMPOUNDS – THE TRIALS AND TRIBULATIONS OF AN EVERYDAY ATOM

HOW DO YOU KNOW HOW MANY ELECTRONS AN ATOM HAS?

You can tell how many electrons are in the outer shell of an atom by looking at where they are located within the A GROUP elements (tall columns)

Elements in GROUP I A have 1 e- in their outer shell

Elements in GROUP II A have 2 e- in their outer shell

Elements in GROUP IV A have 5 e- in their outer shell etc, etc

WHAT MAKES AN ATOM HAPPY?

A “happy” atom is a full atom – i.e. – the old OCTET RULE: All atoms will seek to attain a full outer shell of electrons - and that means 8

EXCEPTION to the OCTET rule : H and He both only need 2 e- in their outer shells to be “happy” and thus full

HOW DOES AN ATOM BECOME HAPPY?

In order for an atom to attain a full OCTET – usually they must give away or take electrons to/from another atom.

Whether it gives or takes depends upon the whether they “see their glass as half-empty, or half-full”

If they have less than 4 e- in their outer shell, they will most likely give them away (and then the shell UNDERNEATH becomes the outer shell – and it’s full, and the atom is happy)

If they have more than 4 e- in their outer shell, they will most likely take some from another atom to attain 8.

WHEN AN ATOM GETS HAPPY, IT BECOMES AN ION

One other thing happens when a NEUTRAL atom gives / takes electrons…. It upsets the balance of +’s and –‘s so the atom itself becomes + (if it gave away some negative things, in this case electrons) or – (if it took some extra negative things, in this case electrons)

When an atom becomes – charged (has some extra electrons) we call it an ANION

When an atom becomes + charges (gave up a few electrons) we call it a CATION

Generally, a charged atom is just called an ION

NOW THAT YOU ARE A HAPPY ION – IT”S TIME TO SETTLE DOWN AND FIND A MATE….

IONS will be on the lookout to find a mate that will counterbalance their charge – you know how it goes – OPPOSITES ATTRACT

Positive ions will pair up with negative ions, IN THE CORRECT RATIO, so that when they unite – they form a NEUTRAL COMPOUND.

Na+ will get together with Cl- to make NaCl

Ca++ needs to find someone like O--, or he needs to find 2 of someone like Cl-