1. Atom Review
The atomic number is ALWAYS the same as the number of protons in a nucleus
To calculate the number of neutrons:
Round off the atomic mass
Calculate: Atomic mass – atomic number = neutrons
Example:
Chlorine – Atomic mass = 36, Atomic # = 17
36 – 17 = 19 (the number of neutrons)
You try with Barium – Atomic mass = 137, Atomic # = 56
137 – 56 = 81

2. Vocabulary Review What is a valence shell? What is a valence electron?
The outermost shell of electrons
What is a valence electron?
Any electrons that occupy the outermost shell... These are the electrons that are involved in bonding
The ones that are not paired are simply called “bonding pairs”… My Bad 
What is an “octet”?
When the valence shell has 8 electrons – the most stable condition for the second or third shell.

3. Ionic Compounds
When a metal and a non-metal combine and there is a transfer of e- between them.

4. Covalent compounds
When 2 non-metals share e- between them so that each of the elements have a full orbit of e-

5. Ions Form from IONIC Compounds.
They are Atoms that have a + or -charge (they are no longer neutral.)

6. When atoms have the same # of protons and electrons – the atom is neutral. And it is called an ATOM.
When an atom loses or gains electrons from another element – it gets a charge and is now called an ION.
Ions from when a METAL and a NON-METAL combine to form a new compound. They create an IONIC BOND between them.
In an ionic bond, e- are transferred (not shared)

7. ION Let’s recap… +1 Or -1 ATOM No charge Neutral
Same # of protons as electrons
ION
Has a charge ( because it has gained or lost e-)
Not Neutral
Protons stay the same, but a different # of electrons +1
Or -1

8. So how did the Ion get a charge?
Every atom in the periodic table wants to be just like the nearest NOBLE GAS, because it has full outer shell of e- and is stable – that is what every atom wants.
Notice that the metals have more electrons than the stable noble gas, and that non-metals don’t have enough electrons to be a noble gas.
So…Metals tend to give up e- to become more stable
Non-metals tend to gain or take e- to become more stable.

9. Let’s look at an example
Sodium (Na) has 11 e-
If Sodium could just find a way to lose 1 e-, then it would look like Neon (a noble gas with 10 e-)
Chlorine (Cl) has 17 e-
If Chlorine could just find a way to gain 1 e-, then it would look like Argon (a noble gas with 18 e-)
If these 2 could meet – it would be a match made in Heaven!! They could bond together and Sodium could give up it’s e- to Chlorine, who would happily accept it and they would both end up like noble gases!!!

10. Atom 11 e- Atom 17 e- ION 10 e- ION 18 e-
So why does Na get a + charge??
Because it gave up an electron ( got rid of a “-” charge) – so it now has 1 more proton than e-, so 1+ charge!
* Remember – Givers of e- are happy – they always end up feeling good for being nice – they end up positive
*Sharing is caring!!
Chlorine is a taker – takers are selfish and end up being negative.
Chlorine has received an extra e-, so it’s got more e- than p+, so it’s 1-.
We form NaCl
Atom 11 e-
Atom 17 e-
ION
10 e-
ION
18 e-

11. Let’s see it happen…
/watch?v=QqjcCvzWww w

12. Two types of Ions
Metals that give up e- to form “+ “charged IONS are called CATIONS
Eg. Mg2+, Li1+, Al3+, etc…
Non-metals that take e- to form “-” charge IONS are called ANIONS
Eg. S2- , F1- , N3-, etc…

13. Let’s recap… Givers of e- They are losing negative charges
Become positive
The # of e- they lose, is the number of + charges they get.
Eg. Give up 3 e- = end up with a 3+ charge
Called Cations
Takers of e-
They are gaining negative charges
Becoming more negative
The # of e- they gain, is the number of - charges they get.
Eg. Take 3 e- = end up with a 3- charge
Called Anions

14. Take a look… +1 P: 11 P: 11 N:12 N:12 Bohr model of a SODIUM “ATOM”
All e- there (11). Na
Bohr model of SODIUM “ION”
1 valence e- gone (now 10 e-)
Na 1+

15. Now you try it… +2 P: 12 P: 12 N:12 N:12
Bohr model of a Magnesium “ATOM”
All e- there (12).
Bohr model of Magnesium “ION”
2 valence e- gone (now 10e-) like Neon
Mg 2+

16. Try again… -2 P: 8 P: 8 N:8 N:8 Bohr model of a Oxygen “ATOM”
All e- there (8).
Bohr model of Oxygen “ION”
2 valence e- added (now 10 e-) –like Neon!
O 2-

17. Let’s Recap…
All elements want to have a full outer shell of valence e-, just like their nearest noble gas.
If an element gives up e-, it becomes an ION with a + charge (CATION)
If an element takes an e-, it becomes an ION with a – charge ( ANION)
Notice that the ion charges of each element are given on your periodic table in the top right hand corner – called the COMBINING CAPACITY.
The combining capacity helps you predict the # of e- the element will gain or lose.

18. But wait a minute…
Notice on your periodic table, that many of the transition metals have more that 1 charge/combining capacity.
That means that they can form ions in more than 1 way. Elements with more than 1 charge are called MULTI-VALENT.
Eg. Iron (Fe) is multivalent because it has a charge of 2+ or 3+, so it can either lose 2 e- or 3 e- to become Fe 2+ or Fe 3+
It just depends on what it bonds with.

19. Bonding
Two types....
Ionic or Covalent

20. Forming Bonds
When two atoms get close together, their valence electrons interact.
Each atom in the compound wants a stable number of valence electrons (like the nearest noble gas).
Lithium gives up an electron to become as stable as helium (valence shell of 2)
Fluorine accepts an electron from lithium to become as stable as neon (valence shell of 8)

21. We call them the Inert Gases (or Noble Gases) because of this.
Helium, neon and argon are atoms which do not react with other atoms because they each have a full outer electron shell (valence shell).
We call them the Inert Gases (or Noble Gases) because of this.
18p
22n 2p 2n
10p
10n
Atomic mass 4 Ne 20 He 2 10 Ar 40 18
2,8
Atomic number
2,8,8
Electrons in the second shell
Electrons in the first shell

22. The Ionic Bond

23. Ionic Bonding
When the valence electrons of a metal and a non-metal come close to each other
the METAL may LOSE its valence electrons
and the NON-METAL may GAIN valence electrons
For example:
Na has 1 electron in its valence shell, Cl wants one more electron because it has 7
Na (the metal) will give its extra electron to Cl (the non-metal) so that they BOTH have the most stable electron shells

24. Sodium Na Chlorine Cl 2,8,1 2,8,7 11 protons 17 protons 12 neutrons23 Na
Chlorine 35 Cl 11 17
2,8,1
2,8,7
11p
12n
17p
18n
Wants to get rid of one electron
Wants to gain one electron
11 protons
17 protons
12 neutrons
18 Neutrons
17 electrons
11 electrons

25. The Sodium atom has 1 Electron in it’s outer shell.Na
Electron count: 2,8,1
Atom +
The Sodium loses 1 electron to leave a complete outer shell.
It is now a Sodium ion with a charge of 1 +
(Na +)
(2,8)+
Ion

26. The Chlorine atom has 7 electrons in it’s outer shell.Cl
Electron count: 2,8,7
Atom -
(Cl - )
The Chlorine gains 1 electron to gain a complete outer shell.
It is now a Chlorine ion with a charge of 1 -
(2,8,8)-
Ion

27. The Ionic Bond Sodium atom Na Chlorine atom Cl Sodium ion (Na +)-
Sodium ion
(Na +)
Chlorine ion
(Cl -)
The sodium atom loses one electron to get a complete outer shell and becomes a positive ion (Na +).
The Chlorine atom gains one electron to attain a complete outer shell and becomes a negative ion (Cl –).
Strong electrostatic forces attract the sodium and chlorine ions to each other = AN IONIC BOND