3d orbital has higher energy electrons than 3p and 3s. In option ‘c’ it has highest number of electrons, there are two unpaired electrons in 3d orbital while 3p has three unpaired electrons.

a theory of atomic structure in which the hydrogen atom (Bohr atom ) is assumed to consist of a proton as nucleus, with a single electron moving in distinct circular orbits around it, each orbit corresponding to a specific quantized energy state: the theory was extended to other atoms.

The p orbitals have slightly higher energy that the s orbital. The 3 d has an energy level higher than 4s and lower than 4p. The orbitals that experience more shielding and have these higher energies will thus be filled later, as the electrons will tend to fill the lowest energy levels first.

Solution : n+l value for 5d and 4f is 7. if b+l is same higher value of n is same higher value of n shows higher energy .

(i) The first shell has only one sub-shell, i.e., 1s, which has only one orbital, i.e., 1s orbital. Therefore, 1p orbital is not possible. (ii) The second sub-shell has two subshells, i.e., 2s and 2p. Therefore, 2s orbitals are possible.

Level 1 does not have a p or d or f sublevel, only an s sublevel. So there is no such thing as 1p or 1d or 1f. To distinguish between the different s sublevels, we call them 1s, 2s, 3s, and 4s. The p sublevels are called 2p, 3p, and 4p.

At the first energy level, the only orbital available to electrons is the 1s orbital, but at the second level, as well as a 2s orbital, there are also orbitals called 2p orbitals.

The answer is (b) 2d . The third energy level, the electrons are located only in the s and p subshell so 2d subshell do not exist.

This means that the second shell has only s- and p-orbitals and no d-orbitals are present. Similar for n = 3, the permissible values of l are 0, 1, 2. Thus, only s, p and d orbitals are permitted and no f-orbital is present in the third shell.

As it has been mentioned, electrons fill orbitals from the lowest energy, to the highest. As you can see, the 4S orbital is filled BEFORE the 3D orbital as it has a lower energy, and therefore 3D has to be placed in the 4th row in the periodic table, after 4S.

The shape of the 4s orbital. That on the left is sliced in half to show the two spherical nodes of the 4s orbital. The shape on the right shows the nodal structure of the 4s-orbital. While still spherical, the higher s-orbitals (5s, 6s, and 7s) are more complex since they have more spherical nodes.