How does a chemical reaction change from start to finish?

A physical Change, such as a state changing or dissolving, does not create a new substance, but a chemical change does.In a chemical reaction the atoms and molecules that interact with each other are called reactants.In a chemical change reaction the atoms and molecules produced by the reaction are called products.only the atoms present in the reactants can end up in the products. No new atoms are created and no atoms are destroyed. Reactants contact each other, bonds between atoms in the reactants are broken,and atoms rearrange and form new bonds to make new products.

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

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