How To Determine The 4 Quantum Numbers From an Element or a Valence Electron

Summary

This video explains how to determine the four quantum numbers (n, l, ml, ms) for any electron in an atom, with a focus on the last valence electron. Using examples like fluorine, iron, and another unspecified element, the video demonstrates how to identify these quantum numbers based on the electron's position in the atom's energy levels, subshells, and orbitals. It provides a clear breakdown of the process, including how to assign values for the magnetic quantum number (ml) and the spin quantum number (ms), making it easier for viewers to understand the quantum mechanical model of electrons.

Takeaways

• 😀 Understanding the four quantum numbers (n, l, ml, ms) is essential for identifying the properties of an electron within an atom.
• 😀 The principal quantum number (n) corresponds to the energy level of an electron. It is simply the number associated with the electron's shell.
• 😀 The angular momentum quantum number (l) corresponds to the type of orbital (s, p, d, f). It defines the shape of the electron's orbital.
• 😀 The magnetic quantum number (ml) determines the orientation of the orbital and can take integer values between -l and +l.
• 😀 The spin quantum number (ms) indicates the electron's spin, which can be either +1/2 or -1/2.
• 😀 For fluorine, with the electron configuration 2p5, n=2, l=1, ml=0, and ms=-1/2 for the last electron.
• 😀 The possible values of ml depend on the value of l: for s (l=0), ml=0; for p (l=1), ml=-1, 0, or 1; for d (l=2), ml ranges from -2 to +2; for f (l=3), ml ranges from -3 to +3.
• 😀 The ml value indicates the specific orbital the electron occupies within a subshell. For example, for fluorine’s 2p5 electron, ml=0, meaning the electron occupies the p-orbital with an orientation of 0.
• 😀 For iron (Fe), with the 3d6 electron configuration, n=3, l=2, ml=-2, and ms=-1/2 for the sixth electron in the 3d subshell.
• 😀 Quantum numbers can be determined for any electron in any element by following these steps: identify the principal quantum number (n), determine the orbital type (l), find the possible values of ml, and determine the spin (ms).

Q & A

What are the four quantum numbers used to describe electrons?

The four quantum numbers are: n (principal quantum number), l (azimuthal quantum number), ml (magnetic quantum number), and ms (spin quantum number).

How do you determine the value of the principal quantum number (n)?

The principal quantum number (n) is determined by the electron's energy level or shell. For example, in fluorine's 2p5 electron, n is 2 because it is in the second energy level.

What is the value of l for the 2p electron in fluorine?

For the 2p electron in fluorine, l is 1 because p corresponds to l = 1.

What are the possible values for ml when l = 1?

When l = 1, the possible values for ml are -1, 0, and 1.

What is the significance of ml in quantum numbers?

The magnetic quantum number (ml) represents the specific orbital within a subshell where an electron is located. For example, p has 3 orbitals (ml = -1, 0, 1), d has 5 orbitals, and f has 7 orbitals.

How do you determine the value of ms?

The spin quantum number (ms) describes the spin of the electron. It can either be +1/2 or -1/2, representing the two possible spin directions: up or down.

How do you assign the quantum numbers for the last electron in fluorine?

For fluorine's 2p5 electron, the quantum numbers are: n = 2, l = 1, ml = 0 (since the 5th electron is in the 0 orbital), and ms = -1/2 (since the electron spin is downward).

In the example of iron, how do we find the quantum numbers for the 3d6 electron?

For iron's 3d6 electron, the quantum numbers are: n = 3, l = 2 (since it’s in the d subshell), ml = -2 (since it's the 6th electron in the 3d subshell), and ms = -1/2 (as the spin is downward).

What determines the range of values for ml?

The range of values for ml is determined by the azimuthal quantum number (l). For any given l, ml can range from -l to +l, including zero.

How do you assign quantum numbers for an electron in the f subshell?

For the f subshell (l = 3), ml can take values from -3 to +3. For example, if focusing on the 5th electron in the f subshell, its ml could be 1, with a spin of +1/2 if the electron's arrow is upward.