Chlorine (Cl) has an atomic number of 17, which means a neutral chlorine atom has 17 electrons. These electrons are arranged in electron shells around the nucleus. The electron configuration of chlorine is:
- 2 electrons in the first shell (1s)
- 8 electrons in the second shell (2s and 2p)
- 7 electrons in the third shell (3s and 3p)
The arrangement of electrons in two neutral chlorine atoms can be depicted as follows:
Electron Shell Diagram for Two Chlorine Atoms
Chlorine Atom 1
- First Shell: 2 electrons (1s²)
- Second Shell: 8 electrons (2s² 2p⁶)
- Third Shell: 7 electrons (3s² 3p⁵)
Chlorine Atom 2
- First Shell: 2 electrons (1s²)
- Second Shell: 8 electrons (2s² 2p⁶)
- Third Shell: 7 electrons (3s² 3p⁵)
Electron Shell Diagram:
Atom 1:
Shell 1: 2 electrons
(1s)
Shell 2: 8 electrons
(2s 2p)
Shell 3: 7 electrons
(3s 3p)
Atom 2:
Shell 1: 2 electrons
(1s)
Shell 2: 8 electrons
(2s 2p)
Shell 3: 7 electrons
(3s 3p)
Prediction of Bond Type
When two chlorine atoms come together, each has 7 valence electrons in its outer shell (third shell). Each chlorine atom needs one additional electron to complete its octet (8 electrons in the outer shell), which leads us to predict that they will form a covalent bond between them.
In a covalent bond, each chlorine atom donates one of its valence electrons to share with the other atom, allowing both atoms to achieve a full outer electron shell. This results in the formation of a Cl₂ molecule.
Summary
- The bond formed between two chlorine atoms is a covalent bond.
- This bonds results in the formation of a diatomic molecule, Cl₂, allowing both atoms to achieve a stable electron configuration with a complete octet.