Which statement best describes a mole? It is 12 units of a given substance.
It contains 6.02 Times. 1023 grams of sodium chloride.
It is the mass of 12 carbon atoms.
It contains 6.02 Times. 1023 particles of a given substance.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

it is stable as it is in group 0 which have full outer shells of electrons