Chemical bonds

Importance

Chemical bonding is key to understanding why atoms stick together, forming molecules and compounds.

Stability

Atoms look for stability:
neutrons=electrons
Complete sublevels.

Valence electrons

Electrons in the highest level of energy (the outermost shell*).
Take part in chemical reactions.
Determine reactivity, electronegativity and number of bonds
Transition metals*

Determine valence electrons

Neutral: Main group number (column)

Example: Carbon

Z= 6
Group IV A.
4 valence electrons

Example: Chlorine

Z= 17
Group VII A.
1s² 2s² 2p⁶ 3s² 3p⁵
7 valence electrons

Octet rule

•The maximum number of electrons in a valence shell is 8

•Atoms will gain or lose electrons to reach 8

•Gain to reach 8

•Lose to reveal full shell (of 8) underneath

Bonding types

•There are three types of chemical bonds:

•Ionic – electrons are given and taken

•Covalent – electrons are shared

•Metallic – electrons flow in an electron sea

Ionic

​Electrons are transferred.
Ion formation.
Metal and non-metal.
Conduct electricity in a solution.

Covalent

​Non metals
Electrons are shared.
Non polar: Shared symmetrically.
Polar: Shared asymmetrically.
It does not conduct electricity.

Metallic

• ​Electrons move freely (sea of electrons).

• Excellent heat and electric conductors
  

Types of bonding and state of matter

Gases:
● Almost all monoatomic (He, Ar). They have a non-polar covalent bond.

Liquids
● They have covalent bonds, except for Br and Hg, which are liquid at room
temperature.
● Polar liquids are miscible between them, and non-polar are miscible between them (the same dissolves the same)
Solids:
● Ionic compounds conduct electricity in solution.
● All metals are solid at room temperature due to the metallic bonding. The exception being Hg