Question

27
The first three periods are
A) Long periods
B) Short periods
C) Moderate periods
D) None of this​

Answer 1

First there is the hydrogen period, consisting of the two elements hydrogen, 1, and helium, 2. Then there are two periods of eight elements each: the first short period, from lithium, 3, to neon, 10; and the second short period, from sodium, 11, to argon, 18.