1. Unit 4: Chemical Bonding

2. Outline Ionic Bonding (Ch.7) Covalent Bonding (Ch.8) Metallic Bonding
Valence electrons
Covalent bond
Positive and negative ions and transition metal ions
Lewis structure of a molecule
Naming molecules
Ionic bonding: Charge on compounds
Structural formulas
Ionic compounds characteristics
Lewis structures for polyatomic ions, Resonance structures
Writing ionic compound formulas
Metallic Bonding
Molecular shapes
Bond polarity
Metallic bond properties
Properties of Covalent compounds
Properties of metals explained by metallic bond
Metal alloys

3. Ionic Bonding
Whenever two atoms or ions are held strongly together, we say that there is a chemical bond between them.
Chemical bond: A force that holds two atoms/ions together.

4. Ionic Bonding
Chemical bonds can form by the attraction between a positive ion and a negative ion, or
they can form by the attraction between the positive nucleus and the negative electrons of another atom.

5. Ionic Bonding
Recall that an electron dot structure is a diagram that shows the number of valence electrons.
“Octet” is a stable arrangement of eight valence electrons in the outermost energy level.
He: 1s2 Other noble gases: ns2np6
Elements tend to react to acquire the stable electron configuration of a noble gas.

6. Ionic Bonding: Ion formation
Positive Ion formation: loses valence electrons
Negative Ion formation: gains valence electrons
(More information on unit 3 lecture slides)
Losing electrons: Always from the highest energy level.
Gaining electrons: Follows Aufbau principle.
Recall: Atoms gain or lose electrons to acquire the electron configuration of the nearest noble gas.

7. Ionic Bonding: Ion formation
Metals:
Metal atoms easily lose valence electrons.
Eg. Group 1, 2, 13
Transition metals have an outer energy level of ns2 and the d sublevel that is filled is in a lower energy level (n-1)d
Transition metals commonly just lose the two s electrons from its valence shell and form the +2 ion.
Transition metals also can lose their d electrons and form a +3 ion too.
Just have to know about it because we can’t predict it.

8. Ionic Bonding: Ion formation
Metals:
Although an octet is the most stable electron configuration, other electron configurations can also have some stability.
“Pseudo-noble gas configuration”: Full s, p and d sublevels.

9. Ionic Bonding: Ion formation
Examples:
Write the electron configuration of the most likely ion and the charge of the ion.
1. Cs: [Xe]6s Ga: [Ar]4s23d104p Ag: [Kr]5s14d Sc: [Ar] 4s23d1

10. Ionic Bonding: Ion formation
Nonmetals:
Gain electrons
Eg. Groups 15, 16, 17
Usually gain but can lose too.
Name: non-metal element “–ide”

11. Ionic Bonding: Ion formation
Examples: Textbook p.209 Q5
Name the following ions.
1. Ag Li Br-
4. Ca S B3+
7. As H Cd2+
10. Se2-

12. Ionic Bonding: Ionic compounds
When a cation and an anion form and them come close to each other, they are attracted to each other by their opposite charges.
An ionic bond is the electrostatic force that holds oppositely charged particles together in an ionic compound.
Ionic compounds are compounds that contain ionic bonds between two different types of ions.

13. Ionic Bonding: Ionic compounds
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14. Ionic Bonding: Ionic compound properties
Physical structure: (What it physically looks like)
In an ionic compound, large numbers of positive and negative ions exist together in a regular repeating pattern that balances the forces of attraction and repulsion between the ions.

15. Ionic Bonding: Ionic compound properties
Physical structure: eg. NaCl
Very organized arrangement
Each sodium ion is surrounded by six chloride ions and vice versa

16. Ionic Bonding: Ionic compound properties
Physical structure:
This 3D arrangement of particles in an ionic compound is called a crystal lattice.
In a crystal lattice, each positive ion is surrounded by negative ions and each negative ion is surrounded by positive ions.

17. Ionic Bonding: Ionic compound properties
Physical properties:
Melting point
Boiling point
Hardness
Electrical conductivity

18. Ionic Bonding: Ionic compound properties
Physical properties:
An ionic compound can’t conduct electricity as a solid, but when dissolved in water, it can conduct electricity.
Electrolytes are substances that can conduct electricity in aqueous solution.

19. Ionic Bonding: Ionic compound properties
Physical properties:
Lattice energy is the energy needed to separate x 1023 ions from an ionic compound.
Larger ions: smaller lattice energy
Larger charges: larger lattice energy

20. Ionic Bonding: Ionic compounds
Many ionic compounds are binary.
This means that they contain only two different elements.
Binary ionic compounds: 1. Metal cation 2. Nonmetal anion.

21. Ionic Bonding: Ionic compounds
Compound formation:
Look carefully at the charges on both the metal cation and the nonmetal anion.
Ionic compounds have an overall charge of zero.

22. Ionic Bonding: Ionic compounds
Compound formation:
Eg. Sodium and chlorine
Eg. Calcium and fluorine
Eg. Aluminium and oxygen
Textbook p. 212 Q7-11

23. Ionic Bonding: Ionic compounds
Another example:
Formation of ionic compound from Boron and Selenium

24. Ionic Bonding: Ionic compound formulas
Writing Formulas:
Since an ionic compound is made up of ions arranged in a repeating pattern, the chemical formula for an ionic compound represents the simplest ratio of the ions involved.
Formula unit

25. Ionic Bonding: Ionic compound formulas
Writing Formulas:
Eg. Magnesium and Chlorine
1. Cation is always written first.
2. Subscripts represent the number of ions of each element in the compound.

26. Ionic Bonding: Ionic compound formulas
Writing Formulas: Monoatomic ions
A one-atom ion.
Common metal and nonmetal ions.
Eg. Groups 1,2,15,16,17

27. Ionic Bonding: Ionic compound formulas
Writing Formulas: Monoatomic ions
Textbook p.221 Q19-23

28. Ionic Bonding: Ionic compound formulas
Writing Formulas: Polyatomic ions
Ions that have more than one atom.
A polyatomic ion acts as an individual ion in a compound and its charge applies to the entire group of atoms.
Polyatomic ions exist as a unit, so do not change the subscripts within the ion.

30. Ion
Name
NH4+
Ammonium
ClO-
Hypochlorite
NO2-
Nitrite
ClO2-
Chlorite
NO3-
Nitrate
ClO3-
Chlorate
OH-
Hydroxide
ClO4-
Perchlorate
CO32-
Carbonate
CrO42-
Chromate
HCO3-
Hydrogen carbonate
Cr2O72-
Dichromate
SO32-
Sulfite
S2O32-
Thiosulfate
SO42-
Sulfate
O22-
Peroxide
PO43-
Phosphate
MnO4-
Permanganate
HPO42-
Hydrogen phosphate
CN-
Cyanide
H2PO4-
Dihydrogen phosphate
BrO3-
Bromate
CH3COO-
Acetate
IO3-
Iodate
C2H3O2-
IO4-
Periodate

31. Ionic Bonding: Ionic compound formulas
Writing Names:
1. Write the name of the cation first.
For transition metals only: Write the “oxidation number” (=charge on the transition metal cation) in brackets next to the transition element’s name.
2. Write the name of the anion next to the name of the cation.

32. Ionic Bonding: Ionic compound formulas
Writing Names:
Eg. Iron, Fe, can be both the Fe2+ and the Fe3+ ion in different compounds.
So the ionic compound FeCO3 would be correctly named as “iron (II) carbonate”
And the ionic compound Fe2(CO3)3 would be correctly named as “iron (III) carbonate”.