The melting of gold is a physical change. why?

Because when a matter melts (or generally speaking, changes phases) its chemical structure does not change. By change of chemical structure I mean, reaction. When a matter melts it does not react with another one. It does not, give or take electrons to another matter or it does not share with them.

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

Show and image of the mixtures or write them