Sublevel
A sublevel is a division of principle energy levels. Theoretically speaking, there are infinite numbers of sublevels, but only four of them are defined which are “s, p, d, and f” where “s” stands for “sharp,” “p” for “principle,” “d” for “diffuse” and “f” for “fine.” These have the characteristic shapes and are used to predict and explain the chemical bonds which atoms can form. The sublevels “p, d and f” have very complex forms while the sublevel “s” is a bit simpler being spherical in shape. The sublevel occupied by any electron is estimated by the electron’s angular momentum quantum number by solving Schrodinger’s equation which allows for finding the distributions for an electron in an atom.

Principle level                      Sublevel

Level 1                                        1s
Level 2                                   2s, 2p
Level 3                               3s, 3p, 3d
Level 4                            4s, 4p, 4d, 4f

In an atom, the electrons, after absorbing energy, get excited and jump to a higher sublevel. The atom energy does not emit emission spectra while absorbing energy. Emission spectra are emitted only when excited electrons around the atom release energy and thus fall to their original sublevel.

Orbital
A sublevel is further divided into orbitals. In an atom, the region of space which has the highest probability of electron is called an orbital. In the case of a hydrogen atom, 99 per cent of the time the electron is found surrounding the nucleus somewhere within a spherical region. One can think of an orbital as being the space where electrons inhabit. An orbital can contain a maximum of two electrons. Thus the “s” sublevel, which has only one orbital, can have only two electrons. Similar patterns are followed in other sublevels as well.

Sublevels                           Number of orbitals                                      Maximum number of electrons
1                                                1(1s)                                                               2
2                                           4(2s, 2p)                                                            8
3                                        9(3s, 3p, 3d)                                                      18
4                                   16(4s, 4p, 4d, 4f)                                                   32

In the case of hydrogen, the orbital which is called “1s” is the one which is occupied by the hydrogen electron. Here, “1”represents the first level orbital in energy level closest to the nucleus while “s” represents the shape of the orbital. Around the nucleus the “s” orbital is arranged in spherically symmetric ways.

The “2s” orbital is same as the “1s” orbital except that the region where there is the greatest possibility of finding the electron is farther from the nucleus and orbital at the second energy level. The less the distance between the electron and nucleus, the lower is the electron’s energy. The 3s, 4s, and 5s orbitals gradually move farther from the nucleus.

Summary:
A sublevel is divided into orbitals.
Orbitals have no defined boundaries but are regions around the nucleus where an electron has high possibilities of being found.

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