Question

Two elements $A$ and $B$ contain $13$ and $8$ protons respectively. If the number of neutrons in them happen to be $14$ and $8$ respectively; the formula unit mass for the compound between $A$ and $B$ unit would be:

• A. $43$
• B. $75$
• C. $102$
• D. $112$

Answer 1

The correct option is C $102$

Two elements A and B contain 13 and 8 protons respectively. They will have 3 and 6 valence electrons respectively and will form A${}^{3+}$ and B${}^{2-}$ ion respectively.
The molcular formula of the compound between A and B will be $A_2{B}_3$.
The atomic mass of A $=13+14=27$
The atomic mass of B $8+8=16$
The formula unit mass for the compound between A and B unit would be $2\left(27\right)+3\left(16\right)=102$
Hence, the option (C) is the correct answer.