A mixture contains 20% iron ions by mass. What mass of iron chloride (FeCl) would you need to provide the iron ions in 50 g of the mixture? A of Fe = 56, A of Cl = 35.5.
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Mass of iron chloride (FeCl₂) : 22.68 g

Proust stated the Comparative Law that compounds are formed from elements with the same Mass Comparison so that the compound has a fixed composition of elements

In the same compound, although from different sources and formed by different processes, it will still have the same composition/comparison

With this law, we can calculate how many grams an element is needed to make a compound with a certain mass, as desired

The iron ions in 50 g mixture :

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

the electron configuration that you gave me has 16 electrons ergo it has 16 protons ergo it is the element sulfur.