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Covalent Bonding
- A bond formed by a shared pair of electrons
Note: “ – “ represents a shared pair of electrons
- Regular covalent bond:
- Each atom involves in the bond donates one electron each to a shared pair
- This shared pair represents one covalent bond
- e.g. HCL = H Cl → H Cl = (H – Cl )
- Multiple bonds:
- Double bond= Forming of 2 shared pairs of electrons between 2 atoms
- Triple bond= Forming of 3 shared pairs of electrons between 3 atoms
- e.g. O₂ = O O → O O = (O – O) 2 pairs
- N₂ = N N → N N = (N – N ) 3 pairs
- Atoms DON’T bond covalently to try to obtain 8 electrons in their outer shell
- Atoms will try to make as many covalent bonds as they have electrons as their outer shell
- To do this, atoms will where possible promote electrons to higher sub levels within the same outer shell, to maximise the number of bonds they can make:
- Boron can only make 1 covalent bond BUT it has a fixed oxidation state of +3
- This tells us boron uses 3 electrons to make bonds
When boron forms compounds, it does this:
- One of the electrons in the lone pair is promoted to a vacant orbital in the “2p” sub level
- To form boron’s BONDING STATE configuration:
- Boron in its bonding state possesses:
- 0 lone pair
- 3 bonding electrons
Dative Covalent Bonding
- When a lone pair of electrons from one atom is donated into a vacant orbital of another atom
- Dative bond arises when one atom donates both electrons to a shared pair
- i.e. It involves the donation of lone pairs of electrons
- There are certain compounds, where 2 atoms are joined together by both regular covalent bonds and dative covalent bonds. E.g. Carbon monoxide(CO)
- Once a dative bond forms, it behaves identical to and is indistinguishable from a regular covalent bond in a compound
- i.e. We can treat dative bonds as if they were covalent bonds
This is the end of the topic!