1. Lecture 9A – Introduction to Chemical Bonding
Roar

2. In nature, only the noble gases tend to exist as isolated atoms
Monatomic – consisting of a single atom
Example:
Neigh
Neon
(Ne)

3. All other atoms like to join to other atoms to form compounds
Depending on how the atom bonds, compounds can be considered 1 - molecules or 2 – ionic compounds

4. Properties of Ionic Compounds
Introduction to Ionic Compounds
Properties of Ionic Compounds
Tend to have high melting / boiling points
Most all exist as Solids at room temp.
Example: NaCl (Salt)

5. Introduction to Ionic Compounds
Ionic Compounds are composed of cations and anions.
Cation – any atom or group of atoms with a positive charge. (metals lose electrons)
Anion – any atom or group of atoms with a negative charge (non-metals gain electrons)

6. Cations: Anions: How can I remember? Cats have Pos (get it?)
Are Negative IONS

7. Who loses, who gains? Cation – has a positive charge
Metallic elements tend to lose electrons
Cation – has a positive charge
Example:
Na has 11 protons, 11 electrons.
To become more stable, Na loses one electron and becomes Na1+
Na1+ has 11 protons, 10 electrons (more like Neon)
When writing this cation: Na1+ and Na+ are the same

8. If metallic elements lose electrons, what do nonmetallic elements tend to do?
Nonmetallic elements tend to gain electrons
Anion – has a negative charge
Example:
Cl has 17 protons, 17 electrons.
Cl would like to be more stable so it gains one electron and becomes Cl1-
Cl1- has 17 protons, 18 electrons (more like Argon)
When writing this anion: Cl1- and Cl- are the same

9. There are many important chemical differences between atoms and their ions!
Example:
Na is a metal and reacts explosively with water
Na+ is a cation and is unreactive in water

10. Naming ions
Cations –
Name of a cation is the same as the name of the element
Example: Sodium (Na) , Sodium ion (Na+)
Anions –
The name of an anion typically ends in –ide.
Example: Chlorine (Cl), Chloride ion (Cl-)

11. Molecular Compounds
Many elements found in nature are in the form of molecules
Molecule – smallest electrically neutral unit of a compound that still has the properties of the compound
. . . Basically they are 2 or more atoms (nonmetals) that act as a unit

12. Examples of Molecules Ozone O3 Diatomic molecules: Composed of 2 atoms
**Remember these:
H2, O2, F2, Br2, I2 , N2, Cl2,
Mr. HOFBrINCl
Triatomic molecules:
Composed of 3 atoms
Example: Ozone, water, carbon dioxide
Oxygen O2
Ozone O3

13. Molecular Compounds Molecular Compounds – compounds composed
of molecules
Mickey Mouse
Just Kidding Water
(H20)

14. Properties of Molecular Compounds
Tend to have low melting / boiling points
Many exist as gas / liquid / solid at room temp.
Most composed of atoms of 2 or more nonmetals
Example: CO2 (Carbon Dioxide)

15. Remember . . . Molecular and Ionic Compounds differ.
Table sugar – molecular compound
Table salt – ionic compound
Which one would melt the first?
It is easy to melt a spoonful of table sugar over an open flame, but it is virtually impossible to do so with salt.

16. Putting it all together
Characteristics of Molecular and Ionic Compound
Molecular Compound
Ionic Compound
Composition
Nonmetals
Metal & Nonmetal
Physical State
Solid, Liquid, or Gas
Solid
Melting Point
Low
High

17. Give the name and symbol of the ion formed when:
A nitrogen atom gains three electrons
Nitride ion, N3-
A calcium atom loses two electrons
Calcium ion, Ca2+
A fluorine atom gains one electron
Fluoride ion, F-