Function isotope 

pub fn isotope(
    symbol: &str,
    mass_number: usize,
    atomic_number: Option<usize>,
) -> MathMultiScript

Build a isotopic symbol.

Input

MathFenced::parentheses(vec![
    isotope("H", 1, None).into(),
    isotope("H", 2, Some(2)).into(),
    isotope("H", 3, None).into(),
]);

Output

$$({}_{}{}^{1}H_{}^{},{}_{}{}^{2}H_{}^{},{}_{}{}^{3}H_{}^{})$$