Mass Number 19
Atomic Number
Elements
Fluorine
Neon
Aluminium
Phosphorus
10
13
15
a. i. Which of the elements would not be capable of forming compounds

Explanation:

The atomic number is the number of protons inside the nucleus of an atom. ... 1.1% carbon 13 with 7 neutrons and a mass of 13.00335 u (measured), and a ... The value given is the mass number of the most stable isotope of that element. ... That's because the chemistry of helium is more like neon (Ne), argon (Ar), etc.

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