Question

Which of the sequences given below shows the correct increasing order of energy?

• A. $3s,3p,4s,3d,5s,5p,4d$
• B. $3s,3p,4s,4p,4d,5s,5p$
• C. $3s,3p,4s,3d,4p,5s,4d,5p$
• D. $3s,3p,4s,5s,3d,4d,5p$

Answer 1

Answer: (C)

$3s,3p,4s,3d,4p,5s,4d,5p$

The energy of an orbital depends on the (n+l) value. Higher is the (n+l) higher is the energy of the orbital.

Value of n majorly decides the energy of an orbital. For two orbitals with the same value for (n+l), the orbital with a higher value of n will have higher energy.

Thus increasing order of energy for orbitals is:

$1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s<5f<6d<7p$

For the given set of orbitals the order is:

$3s<3p<4s<3d<4p<5s<4d<5p$