Question

Certain element X’exist as two isotopes of Atomic mass 20.5 and 21.5 u as 50% abundance each.
The atomic mass of X’ should be
(a) 20.5 u
(b) 21.50
(c)42u
(d)2lu​

Answer 1

20.5 u

maybe this helps you ✨

Answer 2

Answer:

Average atomic mass =

100

∑% abundance × A.M

20.18=

100

20×90+x×21+(10−x)22

2018=1800+21x+220−22x

x=2020−2018

x=2%

Option (A).