Question

A solid gold ring has a mass of 25g. Gold only has one stable isotope of nucleon number 197. How many atoms are there in the gold ring?

(What are the steps?)

Answer 1

Answer:

Gold (79Au) has one stable isotope, 197Au, and 36 radioisotopes, with 195Au being the most stable with a half-life of 186 days. Gold is currently considered the heaviest monoisotopic element (bismuth formerly held that distinction in the belief that the isotope, bismuth-209, was stable; however it is now known to be slightly radioactive).

Main isotopes of gold

(79Au)

Iso­tope Decay

abun­dance half-life (t1/2) mode pro­duct

195Au syn 186.10 d ε 195Pt

196Au syn 6.183 d ε 196Pt

β− 196Hg

197Au 100% stable

198Au syn 2.69517 d β− 198Hg

199Au syn 3.169 d β− 199Hg

Standard atomic weight Ar, standard(Au)

196.966569(5)[1]