The Nature of Covalent Bonds, the Octet Rule, and Lewis Formulas
Covalent Bonds
- When two non-metal atoms approach each other, their nuclei attract the electrons of the other atom.
- Simultaneously, repulsive forces between the nuclei and between the electrons arise.
- At just the right distance, the attractive forces dominate, resulting in a covalent bond.
Definition
Covalent bond
A covalent bond is a chemical bond formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei of the bonded atoms.
- Picture two magnets being drawn together.
- The attraction between their opposite poles is analogous to the forces at play in covalent bonding.
Single, Double, and Triple Bonds
Atoms can share one, two, or three pairs of electrons to form different types of bonds:
- Single bond: One shared pair of electrons (e.g., H₂, where each hydrogen atom contributes one electron).
- Double bond: Two shared pairs of electrons (e.g., O₂).
- Triple bond: Three shared pairs of electrons (e.g., N₂).
- In a water molecule (H₂O), each hydrogen atom shares one electron with oxygen.
- This sharing allows oxygen to complete its octet and hydrogen to achieve a stable configuration with two electrons.
- Triple bonds are shorter and stronger than double bonds, which are, in turn, shorter and stronger than single bonds.
- Keep this in mind when analyzing molecular stability.
Bonds nature will be covered more in detail in the next article.
The Octet Rule
- Atoms often form bonds to achieve a full valence shell, which typically consists of eight electrons.
- This principle, known as the octet rule, reflects the stability of noble gas electron configurations.
Definition
Octet rule
Atoms are driven by their quest for stability, often achieved by attaining a noble gas electron configuration, commonly referred to as the octet rule.
Why the Octet Rule?
The octet rule arises from the stability associated with a filled valence shell.
Example- Carbon (C) has four valence electrons and can form four covalent bonds to complete its octet, as seen in methane (CH₄).
- Oxygen (O) has six valence electrons and forms two covalent bonds to complete its octet, as in water (H₂O).
Exceptions to the Octet Rule
While the octet rule is a useful guideline, there are notable exceptions:
- Incomplete octets:
- Elements like boron (B) and beryllium (Be) are stable with fewer than eight electrons.
