Question

The electron density between 1s and 2s orbital is
A. High
B. Low
C. Zero
D. None of the above

Answer 1

Hint: Electron density is a quantity (number) that describes the electron finding probability at a particular point in space. In a bond, the element which is more electronegative have a greater share of the electrons so, it possesses partial negative charge which reflects its greater electron density. And the element which is less electronegative possesses partial +ive charge which reflects the lack of electron density.

Complete step by step answer:
Let’s discuss the electron density between 1s and 2s orbital. We know that the region between 1s and 2s orbital is a nodal plane. Nodal plane is the region in which the probability of finding an electron is zero. As the region between 1s and 2s orbital is a nodal plane, so electron density is zero.
Hence, the correct choice is option C.

Additional Information:
Let's discuss the electron density in 1s orbital. The shape of 1s orbital is symmetrical, so probability to find an 1s electron at any point depends on the distance of the electron from the nucleus. At r=0 (at nucleus), probability is highest and with increasing distance probability decreases steadily.

Note: It is interesting to note that the distance of maximum probability for 1s electron is the same as the Bohr’s radius for the first orbit. But there is a significant difference in the approach. According to Bohr’s model, the electron revolves at a fixed distance of 53 pm from the nucleus but according to the wave mechanical model, the electron is most likely to be found at this distance but there is always some probability of finding the electron at distances shorter and larger than this.