I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to:

Calculate the atomic mass of hydrogen $\mathrm{A}_r(\mathrm{H})$ (with the r in subscript)

The answer simply summed the mass of each isotope multiplied by its natural abundance. However, the text never mentioned the meaning of $\mathrm{A}_r(\mathrm{H})$ and I couldn't find anything online.

I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to:

Calculate the atomic mass of hydrogen $\mathrm{A}_r(\mathrm{H})$ (with the $r$ in subscript).

The answer simply summed the mass of each isotope multiplied by its natural abundance. However, the text never mentioned the meaning of $\mathrm{A}_r(\mathrm{H})$ and I couldn't find anything online.

I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to:

Calculate the atomic mass of hydrogen Ar(H) (with the r in subscript)

The answer simply summed the mass of each isotope multiplied by its natural abundance. However, the text never mentioned the meaning of Ar(H) and I couldn't find anything online.

Who knows the answer? (And who can tell me how to use subscripts and other formatting tools on stack exchange??)

Thanks!

I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to:

Calculate the atomic mass of hydrogen $\mathrm{A}_r(\mathrm{H})$ (with the r in subscript)

The answer simply summed the mass of each isotope multiplied by its natural abundance. However, the text never mentioned the meaning of $\mathrm{A}_r(\mathrm{H})$ and I couldn't find anything online.