Chapter 11, Problem 28A

Interpretation Introduction

Interpretation: Change in energy when an electron moves from $1s$ to $2s$ is to be explained.

Concept introduction: 3-D space around nucleus in which probability of finding an electron of particular energy is maximum, is called orbital. Quantum numbers are group of 4 numbers which tell everything about electron present in an atom. Principal quantum numbers indicates principal energy level in which electron in present. It is denoted by $n$ .

Answer to Problem 28A

When an electron moves from $1s$ to $2s$ orbital, energy of the electron increases because of reduction in nuclear pull experienced by electron.

Explanation of Solution

In an atom principal quantum number tells about size of orbital, approximate energy of electron in orbital and the number of electron an orbital can contain.

  $n=1$ means electron is present in lowest energy shell as it is closest to nucleus and hence attracted by highest amount nuclear charge.

  $n=2$ means electron is present in second energy shell and little farther in distance from shell 1 and hence attracted by slightly lower amount of nuclear charge than for electron in $n=1$ .

Therefore, when an electron moves from $1s$ to $2s$ orbital, energy of the electron increases because of reduction in nuclear pull experienced by electron.

Conclusion

When an electron moves from $1s$ to $2s$ orbital, energy of the electron increases because of reduction in nuclear pull experienced by electron.