1. Chemistry Topic 6
Chemical Compounds

2. Chemical Compounds There are over 112 elements
These elements can combine into groups of 2, 3, or more to form COMPOUNDS
That is a lot of compounds

3. Chemical Bonds Chemical bonds are what hold elements together
Chemical bonds are formed when elements gain, lose or share electrons

4. Reminders Elements are made of atoms
When Atoms combine they form molecules
Like water ---- H2O (2 Hydrogen and 1 Oxygen)
Atoms are held together by chemical bonds to form molecules

5. Chemical Compounds
A compound is when two DIFFERENT types of atoms come together to form a molecule.
H2O, NaCl
Water and Salt
It takes on properties different than those of the separate elements that compose it

6. Chemical Formulas
A chemical formula uses symbols and numbers to represent the composition of a pure substance
If there is more than one atom of an element, there will be that small number next to the element symbol name
Example: 3 atoms of Carbon C3
Small number shows the number of atoms

7. Writing formulas for chemical compounds
1. Find the element symbol
2. Put the symbols in order of how they are given to you
3. Write the number of atoms needed for each element (small and at the bottom)

8. Ions Ions are CHARGED atoms SO HOW DOES THIS HAPPEN???
Charged means they are either positive or negative.
So far we have been dealing with atoms that are NEUTRAL.
SO HOW DOES THIS HAPPEN???

9. Ions Ions are formed when an atom either LOSES or GAINS electrons.
The electrons don’t just go into outer space never to be seen again, though… so where do they go???

10. Ionic Compounds
Ionic compounds are formed when a METAL gives electrons to a NON-METAL
The atomic process of above example

11. Ionic Compounds Formed from metals and non-metals
Forms ions in solutions
Conducts electricity
Solid at room temperature
Before we learn how to understand ionic compounds we must first learn how many electrons atoms can give and take

12. Let’s look at Sodium (Na)
Na has ONE electron in its outer shell
If a Na ATOM gives away ONE electron what will the charge be of this ION?
We write this Na1+

13. How Ionic Compounds Are Formed
Once an atom give up electrons, it becomes positive
Once an atom takes electrons, it becomes negative Cl
17p+ Na
11p+
11 e-
17 e-

14. Remember… Positives and negatives attract
Once Na becomes Na+ and Cl becomes Cl- , they are attracted to each other
Na Cl-
11 p p+
10 e e-
Overall charge

15. Let’s look at Beryllium (Be)
Beryllium has TWO electrons in its outer shell
Because Metals aren’t greedy, they are okay to give these electrons away.
If a Be ATOM gives away TWO electrons what will the charge be of this ION?
We write this Be2+

16. Non-Metals
Non-metals are GREEDY! They want all the electrons they can get.
There is one exception, though…..

17. Non-Metals
Non-metals are GREEDY! They want all the electrons they can get.
There is one exception, though…. The Noble gases. They have a FULL outer electron shell so they NEVER give away or take electrons. They never form compounds.

18. Let’s look at Nitrogen (N)
Nitrogen has FIVE electrons in its outer shell so it can TAKE THREE more.
(remember, non-metals are greedy and want all the electrons they can get!)
So if an atom of N takes 3 more electrons, what would the charge of this ion be?
We write this N3-

19. Putting it all together
Metals give away electrons
Non-metals take electrons
When a metal gives its electrons to a non-metal they come together to form an ionic compound

20. Examples Sodium Ion (Na1+) Chlorine Ion (Cl1-) Metal Ion Non-Metal Ion
Sodium has a charge of 1+ when it gives its electron away
Chlorine has a charge of 1- when it takes in another electron
If Chlorine takes Sodium’s electron, they come together to form an ionic compound. The ionic compound must have a NEUTRAL charge.
Metal Ion
Non-Metal Ion
Ionic Compound
Na1+
Cl1-
NaCl

21. Examples Magnesium Ion (Mg2+) Chlorine Ion (Cl1-) Metal Ion
Non-Metal Ion
Ionic Compound
Mg2+
Cl1-
THIS DOES NOT BALANCE! WHAT DO WE NEED TO DO?!
Cl Cl1-

22. Examples Aluminum Ion (Al3+) Chlorine Ion (Cl1-) Metal Ion
Non-Metal Ion
Ionic Compound
Al3+
Cl1-
THIS DOES NOT BALANCE! WHAT DO WE NEED TO DO?!
STOPPED HERE 9SA

23. Naming Ionic Compounds
The metal element ALWAYS goes first
The non-metal element goes second but change its ending to –ide.
Example: NaCl ---- Sodium Chlor-IDE
Example: MgCl Magnesium Chloride
9SA and 9SB Stopped HERE – Thursday January 12

24. Metal Ion
Non-metal Ion
Ionic compound
Name
BeF2
Na1+
P3-
Mg2+
Magnesium Oxide
F1-
Beryllium Fluoride
Al2S3

25. Conductivity Ions have charges… Ionic compounds do NOT have charges
If you put an ionic compound in water, it will separate into positive and negative ions
Charged particles carry electric current through water… so they are said to be CONDUCTIVE!

26. Diatomic Molecules
Diatomic molecules are made up of Two atoms of the SAME element.
O – Pure Oxygen
O2 – Oxygen Gas

27. Binary Compounds
Both Ionic and Molecular compounds can be binary compounds
Binary compounds are a compound made of TWO different elements

28. Molecular Compounds
A molecular compound is when two NON-METALS combine.
Hydrogen – H
Carbon – C
Nitrogen – N
Oxygen – O
Fluorine – F
Phosphorus – P
Sulfur – S
Chlorine - Cl

29. How are they named? 1. Write the entire name of the first element
2. Change the ending on the name of the second element to -IDE
3. Use a prefix to indicate the number of each type of atom in the molecule
Chemists are LAZY! If the first one has only one atom, we do NOT include a prefix… let’s look at some examples

30. Prefix Mono One Di Two Tri Three Tetra Four Penta Five Hexa Six Hepta
Seven
Octa
Eight
Nona
Nine
Deca
Ten

31. Examples: 1. CO2 2. CO3 3. H2O 4. P2O7 CARBON DIOXIDE CARBON TRIOXIDE
DIHYDROGEN MONOXIDE
DIPHOSPHORUS HEPTAOXIDE

32. Working in Reverse DISILICON PENTAOXIDE DIHYDROGEN HEXAOXIDE
Si2O5
DIHYDROGEN HEXAOXIDE
TRIPHOSPHORUS OCTACHLORIDE
H2O6
P3Cl8

33. States of Matter Solid – (s) Liquid – (l) Gas – (g) Aqueous – (aq)
IONICS COMPOUNDS ARE TYPICALLY SOLIDS OR AQUEOUS
COVALENT COMPOUNDS ARE SOLID, LIQUIDS OR GASES

34. (s) (g) (l) (aq) Solid sodium chloride Solution of sodium chloirde
NaCl(s)
Solution of sodium chloirde
NaCl(aq)
NaCl(l)

35. Properties of Ionic and Molecular Compounds
Covalent (Molecular)
Formed from metallic and non-metallic elements
Usually formed from only non-metallic elements
Forms ions in a solution
Does not form ions in solution
Conducts electricity
Usually does not conduct electricity
Solid at room temperature
Solid, liquid or gas at room temperature

36. YOUR TURN – Exit Slip Time
Molecular Compound
Name
NO3
Nitrogen Trihydride
F2S4
CN2
Trisulfer Pentachloride
CH4 (Methane)