Which of the five atoms can be described by the following properties: Relative atomic mass is greater than 30 but less than 40, it has odd atomic number and forms a unipositive ion in solution?
A.
T
B.
W
C.
X
D.
Y
E.
Z
Correct answer is D
Y = 19 protons, 19 electrons and 20 neutrons.
Y has electronic configuration 2, 8, 8, 1. Hence, it has one valence electron in the outer shell (Valency of +1).
Mass number = protons + neutrons
= 19 + 20
= 39.