Using the known values for haydrogen atom, calculate
. (a) radius of thirdj orbit for `Li^(+2)`
. (b) speed of electron in fourth orbit for `He^+`
. (c ) angular momentum of electron in 3rd orbit of `He^+.`

Explanation

a. `Z = 3 for Li^(2+)`
Further, we know that
`r_(n) = for (n^(2))/(2) a_(0)`
Subsitituting `n = 3 , z = 3, and a_(0) = 0.529 Å` we have
`r_(3) for Li^(+2) = ((3)^(2))/((3)) (0.529) Å = 1.587 Å`
b. `Z = 2 for He^(+)`. Also , we know that
`v_(n) = (z)/(n) v_(1)`
Substituting `n = 4, z = 2, and V_(1) = 2.19 xx 10^(6) ms^(-1)`, we get
`V_(4) for He^(+) = ((2)/(4)) (2.19 xx 10^(6)) ms^(-1)`
`= 1.095 xx 10^(6) ms^(-1)`