Question

If each atomic orbital can accommodate maximum 5 electrons, then the maximum number of elements possible in `8^"th"` period would be?

(1) 80

(2) 64

(3) 105

(4) 125

Answer 1

The maximum number of elements possible in the 8th period would be (4) 125.

Explanation:

We must derive the electron configuration of the 8th period, assuming that the orbitals follow the (`"n+l"`) rule.

The order of orbitals in the eighth period would be

`"8s"color(white)(l)"5g"color(white)(l)"6f"color(white)(l)"7d"color(white)(l)"8p"`

The number of electrons in each orbital is

`ulbb("Orbital"color(white)(m)"Electrons"color(white)(m))`
`color(white)(mll)"8s"color(white)(mmll)1×5 =color(white)(ll)5`
`color(white)(mll)"8p"color(white)(mml)3×5 =color(white)(l) 15`
`color(white)(mll)"7d"color(white)(mml)5 × 5 =color(white)(l) 25`
`color(white)(mll)"6f"color(white)(mmll)7 × 5 =color(white)(l) 35`
`ul(color(white)(mll)"5g"color(white)(mml)9 ×5 =color(white)(l) 45)`
`color(white)(mmmmm)"Total" = 125`

Thus, there would be 125 elements in the eighth period.