Which of the following is an alkali?
A
Neon
B
Chlorine
C
Sodium
D
Helium
Correct Answer: Sodium
Neon (2s22p6) and Helium (2s2) both have inert gas electron configuration, thus, both are inert gases. Chlorine (3s23p5) has one electron short of a closed shell, thus, chlorine is a halogen. Sodium (3s1) a single electron outside the closed shell, therefore, sodium is an alkali.