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Investigate 1 + 2
The elements Li, Na, K all have the lowest 1 st ionization energy
That means it’s REALLY easy for them to lose one electron (they are the lowest points on your graph).
After they have lost that 1 electron, then they have a COMPLETE OCTET. I,e they have a Noble Gas Configuration. They are ‘happy’
Investigate 1 + 2
It is really hard for Li, Na, K to lose a second electron. Not only do they have to break apart the OCTET, but they have a +1 charge, so the electrons are pulled even tighter by the nucleus. Losing a second electron is the highest point on the second graph.
Be, Mg, Ca all have 2 valance electrons
They will need to lose 2 electrons to get the complete OCTET.
The first electron comes away pretty easily, and the second really easily so that it has a NOBLE GAS CONFIGURATION.
Note – the ionization energy DECREASES as you move down a group because adding another ‘layer’ means the electrons are further from the nucleus – so easier to remove.
So – what’s the point?
Atoms are stable when they have the electron configuration of a NOBLE gas. They will gain or lose their VALANCE electrons in order to do this. In general, this means a stable atom has 8 valance electrons, or an OCTET.
Now we can predict formulas!
Zinc wants to lose 2 electrons
Each Chlorine wants to gain 1 electron.
So in order for all the atoms to be ‘happy’ you need 1 Zinc for every 2 Chlorines.
The formula is
Al wants to lose 3
F wants to gain 1
What is the formula for Aluminum Fluoride?
Na 2 O
K 3 N
The OCTET RULE states that atoms gain or lose electrons to get a complete OCTET.
Naming Binary Compounds
1. Always name the Cat-ion (+) first.
2. The Anion is second, and the ending changes to -ide
Ex: Copper Chlor ide
Sodium Ox ide
Potassium Nitr ide
Electrons are transferred from one atom to another. The first atom becomes (+) the second becomes (-)
The compound holds together because (+) and (-) charges attract each other.
Electrons are shared between 2 atoms. There are no ions.
The molecule holds together because the electrons ‘tie’ them together by forming molecular orbitals , not atomic orbitals.
Electron Dot Structures
We can figure out how atoms will form covalent bond by drawing its Electron Dot structure. This is a drawing of how the electrons from each atom interact with each other.
Steps to drawing Lewis Dot structures
1. Draw out all the atoms with the valance electrons shown as dots
Decide how they will share to form bonds so that ALL the atoms have a complete octet (note - Hydrogen will be stable with only 2 electrons, since it is the 1s level)
Re-write the structure with the bonding electrons represented as lines.
This is REALLY easy - it just takes practice - I promise!