If one uses an analytical balance to measure out a small quantity of reagent, and the mass is 0.0256 g, then how many significant figures are present?

3

Explanation:

There are 3 significant figures and four decimal places. How do you know how many significant figures? Now let us convert the given number to standard form; we have 2.56*10^-2. Only the two significant figures were shown.

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