Question

Consider the nuclear equation below.

Superscript 235 subscript 92 upper U right arrow superscript 4 subscript 2 upper H e.

What is the nuclide symbol of X?
Superscript 231 subscript 94 upper P u.
Superscript 235 subscript 90 upper T h.
Superscript 239 subscript 94 upper P u.
Superscript 231 subscript 90 upper T h.

Answer 1

Use conservation of mass and charge.

Mass: 235 = 4 + A_X → A_X = 231.
Charge: 92 = 2 + Z_X → Z_X = 90 (element 90 = Th).

So X = 231/90 Th (thorium-231).