Question

Consider the nuclear equation below.

Variable X right arrow superscript 228 subscript 89 upper A c plus superscript 0 subscript negative 1 beta.

What is the nuclide symbol of X?
Superscript 230 subscript 90 upper T h.
Superscript 229 subscript 89 upper A c.
Superscript 228 subscript 90 upper T h.
Superscript 238 subscript 88 upper R a.

Answer 1

Use conservation of mass and charge.

Mass number: A_X = 228 + 0 = 228.
Atomic number: Z_X = 89 + (−1) = 88.

Z = 88 is radium (Ra), so X = 228_88Ra.

None of the given choices match exactly (the last choice is 238_88Ra, which has the wrong mass number).