Atomic Structure: Ions

All atoms are neutral, but when they have a higher or lower number of electrons compared to protons, they become CHARGED IONS. These are divided into two groups:

Cations — Positively charged ions
Anions — Negatively charged ions

How to remember which is which? Just remember that ANIONS are A-Negative-ION. Wallah, so genius, I know.

TRENDS...

• Elements in group 1 to 4, all their atoms tend to lose an electron to complete their shells. Meanwhile, Elements in group 5 to 7, all their atoms tend to gain an electron.
• All metals are cations. All non-metals are Anions.

To help remember their charge, we can always go back to that beautiful valency table we had in the last post!

Atomic Structure: Valency

So remember in the last post when we talked about ELECTRON SHELLS? Remember that they could have many many many shells, and yet a maximum number of electrons in each shell? If you don't it's okay, we'll recap.

So basically, the way electrons are arranged in an atom is also called electronic configuration. If you want to represent it visually, it'd look like this:

If you want it in orbital notation it'd look like this:

I would continue with spdf and all but that's for another day. ANYWAYS...

The circles you see with the x's on them? That's called a shell. And those x's are electrons. So the first shell can hold up to 2 electrons and the second and subsequent ones can hold up to 8 electrons. Now, now, here's the complicated part.

A VALENCE ELECTRON is an electron that lies on the outermost shell of an atom. The outermost shell is also called the "valence shell". So what is this complicated "valency"?

Valency --> No. of electrons needed to be gained or lost to complete the shell

"Complete the shell?" Simi lanjiao. 

"Completing the shell" means making the shell is full. So for example, iodine, has seven valence electrons yes? To complete the shell, you need to gain another electron, to ensure you have the maximum number of electrons in the shell (8).

Here's the complicated part. Sometimes an ion will also lose electrons to complete the shell. In the case of lithium for example, a lithium ion has only one valence electron. So what does it do to complete the shell? It loses that electron. 

Why does it do that? Because losing one electron is easier than gaining seven more. (informal answers you must not use in exam) BUT YES, VALENCY IS COMPLICATED. So here's a little valency table for you:

Things to note:

Down the group, elements all have the same number of valence electrons. 

However, number of valence shells increase down the group.

Across the period, number of valence electrons increase

Why does all this happen? Moving on to electron affinity...

Atomic Structure: Parts of an Atom

So before we delve into the deep and confusing processes, we need to know the parts of an atom, also known as SUB-ATOMIC PARTICLES.

Okay so parts of the atom...

THE NUCLEUS
This is made up of protons and neutrons.

THE ELECTRON SHELL
The electron is just a rough gauge for where the electrons move. The inner most shell can carry up to 2 electrons, while the ones further away can carry up to 8 electrons. And you can have many many many electron shells, but we'll get to that later.

ALL THE LITTLE 'ON'S
Protons — Determine the identity of the atom (like on the periodic table)
Electrons — Determine the charge of the atom (the less you have, the more positive the charge. Vice versa)
Neutrons — Determine the mass of the atom

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Okay, so maybe I'm not very good at describing and you might still be wondering:

So let's put a little link to the periodic table. So on the periodic table they usually give you a little bit of information on each element. For example, carbon here, on this lovely image I found on Google.

So like the diagram says, the number above the letter, that is the atomic number, AKA proton number. This is, as you might've guessed, the number of protons in that atom. And if you haven't noticed, this is how elements in the periodic table are arranged: By proton number.

The number below that is the nucleon number or atomic mass. You might wonder, why is this the mass?? Remember that ATOMS ARE ELECTRICALLY NEUTRAL. Sooooo... in every atom, there will be an equal number of protons and electrons, cancelling each other out. So what's the only thing that actually has mass? That's right, your good old buddy neutrons.

If an atom does not have an equal amount of protons and electrons, it will be an ion, which we'll be covering in the next post!