Class Notes (1,100,000)
CA (650,000)
UTSC (30,000)
Chemistry (600)
CHMA10H3 (200)
Lecture 18

CHMA10H3 Lecture Notes - Lecture 18: Lewis Structure, Bravais Lattice, Lattice Energy


Department
Chemistry
Course Code
CHMA10H3
Professor
Marco Zimmer
Lecture
18

This preview shows half of the first page. to view the full 2 pages of the document.
CHMA10- Lecture 18 (Feb. 27th)
- Chemical Bonding (basic concepts)
Chemical bond: it exists between two atoms of groups of atoms if the forces between
them cause them to form an aggregate with sufficient stability to make it convenient to
regard it as an independent molecular species
What must a theory of bonding do?
1. Explain why bonds form between some atoms and not others
2. Explain why multiple compounds can form between the same elements
3. Account for the different shapes of molecules (e.g. some are linear, and some
are angular)
4. Rationalize the strengths of different bonds
5. Rationalize changes in bonding that occur during reactions
Types of Bonding
Ionic bonding
Covalent bonding
Metallic bonding (“sea of e-“)
Lewis Bonding Theory
Emphasizes valence e- to explain bonding
“Atoms adjust their electron counts during a chemical reaction in order to
become isoelectronic with a noble gas”
Allows use to predict many properties of molecules (e.g. molecular stability,
shape, size, polarity)
Two options to get to octet:
Gaining/losing electrons (ionic model)
Sharing electrons (covalent model)
Lewis Dot Structures
When atoms form chemical bonds, ONLY their outer regions come into contact
Use dots to keep track of the valence electrons
Ionic Bonding
Ionic bond: electrostatic force that holds ions together in an ionic compound
I. E.g. lithium, LiF
II. Each element will be most stable with a complete octet
Energetics of Forming Ionic Compounds
The formation of ionic compounds is exothermic
Should always consider lattice energy (the energy released when gas phase ions
coalesce into a crystalline lattice)
Lattice Energy: Why Should you Care?
When an ionic compound forms, it arranges all the ions in a regular, repeating
pattern called a crystal lattice
Each cation is surrounded by anions
Crystal lattice is held together by electrostatic attraction of the cations
for the surrounding anions
You're Reading a Preview

Unlock to view full version