Final answer:
The electronic configuration of sodium is [Ne]3s¹, and chlorine is [Ne]3s²3p⁵. In forming monatomic ions, sodium becomes Na⁺ ([Ne]) and chlorine becomes Cl⁻ ([Ar]). These configurations follow the octet rule for stability with full valence shells.
Step-by-step explanation:
The electronic configurations of sodium (Na) and chlorine (Cl) are as follows:
- Sodium has the electronic configuration of 1s²2s²2p⁶3s¹. In shorthand using the noble gas preceding it, this is written as [Ne]3s¹.
- Chlorine has the electronic configuration of 1s²2s²2p⁶3s²3p⁵. In shorthand, using the noble gas preceding it, this can be written as [Ne]3s²3p⁵.
When sodium forms a monatomic ion, it loses one electron to achieve the noble gas configuration of neon, resulting in Na⁺ with configuration [Ne]. Similarly, chlorine gains one electron to complete its octet and achieve the noble gas configuration of argon, resulting in Cl⁻ with configuration [Ar].
The octet rule suggests atoms are more stable with a full valence shell, which typically results in a noble gas configuration, and a small charge is generally more stable than a large one. Hence, rather than transferring seven electrons, Na loses one, and Cl gains one.