Calculate the energy associated with the first orbit of `He^(+)`.What is the radius of this orbit ?
Hint `: E_(n) = - 2.18 xx10^(-18) ((Z^(2))/( n^(2))) J //`atom
`He^(+) ( Z=2)`
`r_(n) = ( 52.9(n^(2)))/(Z) ` pm

Explanation

`E_(n)=-((2.18xx10^(-18)J)Z^(2))/n^(2)"atom"^(-1)`
for `He^(+),n=1 , Z=2`
` E_(1) =-((2.18xx10^-18 J)(2^(2)))/1^(2)=-8.72xx10^(-18)J`
the radius of the orbit is given by equation (2.15)
`r_(n) = ((0.0529nm)n^(2))/Z`
since n=1 , and Z = 2
` r_(n) =((0.0529 nm)1^(2))/2 = 0.02645 nm `