Question

The letters X, Y and Z represent different atoms.
40 39 40
X Y Z
19 19 20
What can be deducted from the proton numbers and nucleon numbers of X, Y, and Z?

• A. X and Y are the same elments
• B. X and Z are the same elements
• C. X has more protons than Y
• D. Z has more neutrons than Y

Answer 1

The correct option is A X and Y are the same elments

${}_{19}^{40}X$ ${}_{19}^{39}Y$ ${}_{20}^{40}Z$

	X	Y	Z
Number of protons (Z)	$19$	$19$	$20$
Number of electrons	$19$	$19$	$20$
Number of neutrons (A – Z)	$21$	$20$	$20$

Since elements $X$ and $Y$ have same $Z$ i.e same atomic number. Therefore they are same elements but different isotopes (i.e they differ in number of neutrons)