NEET Practice Questions (MCQs) with Answers & Solutions

The NCERT text states, 'The shapes of the first four d-orbitals are similar to each other, where as that of the fifth one, $d_{z^2}$, is different from others, but all five 3d orbitals are equivalent in energy.'

The NCERT text states, 'The number of nodes are given by the n –2, that is number of radial node is 1 for 3p orbital, two for 4p orbital and so on.' This formula refers to radial nodes specifically for p-orbitals (where l=1). The general formula for radial nodes is $n-l-1$, so for p orbitals, it is $n-1-1 = n-2$.

The NCERT text explicitly states, 'According to the German physicist, Max Born, the square of the wave function (i.e., $ψ^2$) at a point gives the probability density of the electron at that point.'

The NCERT text says, 'It may be noted that for 1s orbital the probability density is maximum at the nucleus and it decreases sharply as we move away from it.'

The NCERT text states, 'It is also observed that the size of the s orbital increases with increase in n, that is, 4s > 3s > 2s > 1s and the electron is located further away from the nucleus as the principal quantum number increases.'

The NCERT text explains, 'Boundary surface diagram for a s orbital is actually a sphere centred on the nucleus. In two dimensions, this sphere looks like a circle. It encloses a region in which probability of finding the electron is about 90%. Thus, we see that 1s and 2s orbitals are spherical in shape. In reality all the s-orbitals are spherically symmetric.'

The NCERT text mentions, 'the total number of nodes are given by (n–1), i.e., sum of l angular nodes and (n – l – 1) radial nodes.'

According to the table in the NCERT, for l=0, the orbital is denoted by 's'. So, n=4, l=0 corresponds to a 4s orbital.

The NCERT text states, 'azimuthal quantum number. ‘l’ is also known as orbital angular momentum or subsidiary quantum number. It defines the three-dimensional shape of the orbital.'

The NCERT text says, 'Since there are three p, five d and seven f orbitals, therefore, the pairing of electrons will start in the p, d and f orbitals with the entry of 4th, 6th and 8th electron, respectively.' For d-orbitals, pairing starts with the 6th electron, as there are 5 d-orbitals, and each gets one electron before pairing begins.