3.5.5 - Composição do orbital atômico: Número quântico magnético (Orientação espacial dos orbitais)

Summary

This video explains the concept of quantum numbers, focusing on the magnetic quantum number (ML) and orbital shapes. It covers the different sublevels (S, P, D, F) and the number of orbitals associated with each: 1 for S, 3 for P, 5 for D, and 7 for F. The magnetic quantum number defines the orientation of these orbitals in space, with each sublevel having degenerate orbitals, meaning all orbitals within a sublevel have the same energy. The video further demonstrates how orbitals orient themselves in three-dimensional space and how their shapes and sizes differ depending on the sublevel, helping to visualize atomic structure.

Takeaways

• 😀 The magnetic quantum number (ml) describes the orientation of orbitals in space.
• 😀 The values of ml depend on the angular momentum quantum number (l). For example, if l = 0 (s sublevel), ml = 0.
• 😀 The p sublevel (l = 1) has three possible orientations (ml = +1, 0, -1), so it contains three orbitals.
• 😀 The d sublevel (l = 2) has five possible orientations (ml = +2, +1, 0, -1, -2), so it contains five orbitals.
• 😀 The f sublevel (l = 3) has seven possible orientations (ml = +3, +2, +1, 0, -1, -2, -3), so it contains seven orbitals.
• 😀 The orientation of orbitals like p, d, and f in space gives rise to distinct shapes and patterns.
• 😀 When an electron occupies an orbital, it can choose any orientation within a sublevel because all orbitals in a given sublevel have the same energy.
• 😀 Orbitals within the same sublevel and energy level are called 'degenerate orbitals', meaning they share the same energy.
• 😀 The s orbital is spherical, meaning its orientation in space doesn’t affect its shape (ml = 0).
• 😀 The p orbitals are oriented along different axes (x, y, z), with each orbital representing a different orientation.
• 😀 The shapes and sizes of orbitals increase with higher energy levels, such as the increasing size of orbitals in the 3d and 4f sublevels.

Q & A

What is the meaning of the quantum number ML?

ML is the magnetic quantum number, which determines the orientation of orbitals within a sublevel. It is denoted by values ranging from -l to +l, where l is the azimuthal quantum number associated with the orbital's shape.

What values can ML take for each sublevel?

For each sublevel, ML takes values from -l to +l. For example, for the s sublevel (l = 0), ML can only be 0. For the p sublevel (l = 1), ML can be -1, 0, or +1. For the d sublevel (l = 2), ML can be -2, -1, 0, +1, or +2, and for the f sublevel (l = 3), ML can range from -3 to +3.

How does the number of orbitals relate to the value of l?

The number of orbitals in a sublevel is directly related to the value of l. For example, an s sublevel (l = 0) has 1 orbital, a p sublevel (l = 1) has 3 orbitals, a d sublevel (l = 2) has 5 orbitals, and an f sublevel (l = 3) has 7 orbitals.

Why does the s orbital only have one possible orientation?

The s orbital is spherical in shape and does not have any directional orientation in space. Therefore, it only has one possible orientation, which corresponds to ML = 0.

What is meant by the term 'degenerate orbitals'?

Degenerate orbitals refer to orbitals within the same sublevel that have the same energy. For instance, in the p sublevel, the three orbitals (px, py, pz) are degenerate because they have the same energy.

How does the electron decide which orbital to occupy within a sublevel?

Electrons do not have a preference for which orbital they occupy within a sublevel as long as all orbitals are degenerate (have the same energy). Electrons can occupy any of the available orbitals, and the choice is essentially random due to the same energy level.

What is the significance of the different shapes of orbitals (s, p, d, f)?

The different shapes of orbitals (spherical for s, dumbbell-shaped for p, cloverleaf for d, and complex for f) represent the different spatial orientations and the regions in space where electrons are likely to be found. These shapes are determined by the quantum numbers, particularly the azimuthal quantum number (l).

What does the term 'orbital orientation' refer to?

Orbital orientation refers to the specific spatial direction an orbital can take within a given sublevel. For example, in the p sublevel, there are three orbitals (px, py, pz), each oriented along one of the axes in three-dimensional space (x, y, z).

How does the size of orbitals change with different energy levels?

The size of orbitals increases with higher energy levels. As the principal quantum number (n) increases, orbitals become larger, which corresponds to electrons being farther from the nucleus in higher energy states.

Why are there more orbitals in higher sublevels like d and f compared to s and p?

Higher sublevels like d and f have more orbitals because the value of the azimuthal quantum number (l) increases, allowing for more possible orientations. For example, d (l = 2) has 5 orbitals, and f (l = 3) has 7 orbitals, compared to p (l = 1) with 3 orbitals and s (l = 0) with just 1 orbital.