### Learn quantum physics online

Spectral fine-structure lines in quantum physics suggested that the energy levels of an electron are more complex than a consideration of the electrostatic interactions from the Bohr hydrogen energy level and the Sommerfeld model. In this article, we can study four quantum numbers for study online college courses.Magnetic interactions comparatively small in magnitude are responsible for the fine structure defects of an atom.

The closer examination of the atomic spectra demanded further refinement of the atomic orbitals. It was found that under high resolution the spectral lines of alkali metals had a fine structure of an atom.

Study the fine structure of an atom four

**quantum number**needed to explain the various spectra.

These quantum numbers are the identification numbers for an individual electron in an atom to describe the position and energy level of an atom.

In order to study the size, shape, orientation of energy levels or orbital four quantum numbers are necessary. These quantum numbers are

- Principal quantum number
- Azimuthal quantum number
- Magnetic quantum number
- Spin quantum number.

#### How to find the principal quantum number?

The principal quantum number describes the energy level or the principal shell to which an electron can stay. The principal quantum number denoted by n.The primary importance of the principal quantum number for determining the size of an atom and energy of an electron. From Bohr's model, the energy value of the hydrogen energy level is fixed by the fixed value of n.

Another multielectron atom energy value of each electron depends mostly on the principal quantum number of an atom.

As the value of the principal quantum number increases the atomic radius or nucleus electron separation increases and the energy also raised.

The principal quantum number is always an integer and can assume the value, 1, 2, 3, 4.... but not zero.

n = 1, 2, 3, 4, 5, ............... ∞.

#### Azimuthal quantum number formula

This quantum number was introduced by Sommerfeld in his atomic model and gives the angular momentum of an electron in its elliptical movement around the nucleus of an atom and fine structure of the hydrogen spectrum.The general geometric shapes of an electron cloud or orbital are described by the azimuthal quantum number or angular momentum quantum number. Permitted values of l for a given value of n has 0 to (n-1).

∴ l = 0, 1, 2, 3.....(n-1)

The total number of different values of l equal to n.

n = 1, l = 0 (1S-subshell)

n = 2, l = 0, 1 (2S and 2P-subshell)

n = 3, l = 0, 1, 2 (3S, 3P, and 3d-subshell).

The total number of different values of l equal to n.

n = 1, l = 0 (1S-subshell)

n = 2, l = 0, 1 (2S and 2P-subshell)

n = 3, l = 0, 1, 2 (3S, 3P, and 3d-subshell).

#### What does the magnetic quantum number determine?

Bohr's model could not explain the splitting of a single spectral line into a number of closely spaced lines in presence of magnetic field or presence of the electric field.The presence of more lines in the spectrum of the magnetic field or electric field indicates the energy levels are further subdivided by the additional quantum number called magnetic quantum number.

The magnetic quantum number associated with the orientation of the electron cloud with respect to a given direction, usually that of a strong magnetic field. This quantum number denoted by ml.

A given value of the azimuthal quantum number, the magnetic quantum number can have any integral value between +1 to -1.

∴ m

_{l}= + l, (l - 1), ..... 0 ..... - 2, - l#### Spin quantum number in chemistry

When spectral lines of hydrogen, lithium, sodium, and potassium observed by the instrument of high resolving power, each of the lines of the spectral series was found to consist of a pair of lines known double line structure.To describe these double lines of the fine structure another fourth quantum number necessary and it is known as a spin quantum number.

The electron itself regarded as a small magnet. A beam of a hydrogen atom can be split into two beams by a strong magnetic field. This indicates that there are two kinds of spin that can be differentiated on the basis of their behavior in a magnetic field.

The electron can either spin clockwise or counterclockwise. The two directions of spin represent as(↑↓).

The spin quantum number independent of the other three quantum numbers. Two directions of spin are represented as (↑↓) can have two possible spin quantum number values (+ ½) and (- ½) depending on the direction of rotation of the electron about its axis.

### How to find quantum numbers of an element?

Quantum numbers of an atom |

What are the four quantum numbers of the 19th electron of chromium?

Answer

The atomic number of chromium 24 and the electronic configuration of chromium

1S² 2S² 2P⁶ 3S² 3P⁶ 4S¹ 3d⁵.

19th electron means 4S¹ electron.

n = 4, l = 0, m = 0, and s = +½ for 4S electron.

∴ Quantum numbers set for 19th electron of chromium

4, 0, 0, +½.

19th electron means 4S¹ electron.

n = 4, l = 0, m = 0, and s = +½ for 4S electron.

∴ Quantum numbers set for 19th electron of chromium

4, 0, 0, +½.

Question

What is the correct set of four quantum numbers for the valence electron of rubidium?

Answer

The correct set of four quantum numbers for the valence electron of the rubidium atom

5, 0, 0, +½

Question

How many electrons in an atom can have the following quantum numbers n = 4 and l = 1?

Answer

6 electrons in an atom can have the following quantum numbers n = 4 and l = 1.

Question

How many possible numbers of orbitals of an atom when n = 4?

Answer

Number of possible orbitals when n = 4

[1(4S) + 3(4P) + 5(4d) + 7(4f)]

= 16.

[1(4S) + 3(4P) + 5(4d) + 7(4f)]

= 16.

Question

How many possible orbitals are there when n = 3, l = 1, and m

_{l}= 0 ?

Answer

The number of possible orbitals = 1.

Online college chemistry courses

- Chemical equilibrium
- Law of mass action
- Chemical kinetics
- Properties of gases online
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### How are the shapes of atomic orbitals determined?

**Atomic orbitals**are the basic building blocks of the atomic orbital diagram or alternatively known as the electron cloud or wave mechanics model.

According to the electron cloud model, an orbital is a region in space where the probability of finding an electron maximum.

The probability of finding the electron cloud in 1S orbital of the hydrogen atom at certain positions near the nucleus of the hydrogen atom and electron density is maximum in the region just surrounded the nucleus of an atom.

According to the electron wave model, the wave function of the electron in an atom is called orbital. The wave function is plotted against distance and space in three dimensional marked by a curve will give the orbital diagram of an atom.

The probability of finding an electron in space around the nucleus involves two aspects, radial probability, and angular probability.

It is not possible to represent completely in one diagram on paper the directional properties of electron orbital. An angular probability distribution must be combined mentally to have an overall shape of the orbital.

#### How many orbitals are in the s sublevel?

The angular probability distribution is greater interact and importance for S-subshell. The S-electron has no angular dependence because the relevant wave function is independent of angles Î¸ and Î¦.S-subshell of an atom |

The electron cloud distribution in S-subshell has a spherically symmetrical probability distribution.

#### Orbital diagram of p-subshell of an atom

P-subshell of an atom |

P-subshell designated as Px, Py and Pz are mutually perpendicular and they are concentrated along the respective coordinate axis X, Y and Z.

Unlike the S-subshell, the angular part of the P wave is dependent on Î¸ and Î¦ and P-subshell is shielding by S-subshell.

#### The shape of d-subshell of an atom

d-subshell of an atom |

l = 2(d - orbital),

ml = -2, -1, 0, 2, 1.

d - subshell has five orientations in space.

Absence of magnetic field all these five d-subshell are equivalent in energy level and this d-subshell said to be five-fold degenerate energy level of an atom.ml = -2, -1, 0, 2, 1.

d - subshell has five orientations in space.