Selenium’s Orbital Notation: Explained Simply!

Understanding atomic structure requires a firm grasp of orbital notation. Linus Pauling, a renowned chemist, significantly contributed to our understanding of chemical bonding and the principles underlying the arrangement of electrons. The concept of electron configuration, represented through orbital notation, directly impacts the chemical properties of elements, including selenium. Furthermore, readily available online tools like orbital diagrams visually represent these configurations, aiding in the comprehension of orbital notation for selenium and other elements.

Image taken from the YouTube channel Wayne Breslyn (Dr. B.) , from the video titled How to Write the Atomic Orbital Diagram for Selenium (Se) .

Understanding Orbital Notation for Selenium

Selenium (Se), with an atomic number of 34, has a fairly complex electronic configuration. Deciphering its electron arrangement using orbital notation provides valuable insights into its chemical behavior and bonding characteristics. This explanation aims to simplify the concept of "orbital notation for selenium" and break down its structure.

What is Orbital Notation?

Orbital notation is a shorthand method of representing the electronic configuration of an atom. It illustrates how electrons are distributed among the various energy levels and sublevels within an atom. These energy levels are called shells, and the sublevels within each shell are called orbitals.

Shells (Energy Levels)

• Represented by the principal quantum number (n), where n = 1, 2, 3, etc.
• Higher ‘n’ values correspond to higher energy levels and greater distances from the nucleus.

Sublevels (Orbitals)

• Within each shell, electrons occupy sublevels designated as s, p, d, and f.
• Each sublevel corresponds to a specific shape and spatial orientation.
• The number of orbitals in each sublevel is fixed:
  • s sublevel: 1 orbital (can hold up to 2 electrons)
  • p sublevel: 3 orbitals (can hold up to 6 electrons)
  • d sublevel: 5 orbitals (can hold up to 10 electrons)
  • f sublevel: 7 orbitals (can hold up to 14 electrons)

Determining Selenium’s Electron Configuration

Before writing the orbital notation, we need to determine the full electron configuration of selenium. Remember that we fill orbitals according to the Aufbau principle, which states that electrons first occupy the lowest energy orbitals available. Hund’s rule also applies, which states that electrons individually occupy each orbital within a sublevel before doubling up in any one orbital.

1. Atomic Number: Selenium has an atomic number of 34, meaning it has 34 protons and, in a neutral atom, 34 electrons.

2. Filling Orbitals: We start filling orbitals, following the order dictated by the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.

3. Electron Configuration: Therefore, Selenium’s full electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴

Selenium’s Orbital Notation: Breaking it Down

The electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴) is already a type of orbital notation, though a concise one. To visualize the orbitals more distinctly, we can expand the notation.

Visual Representation of Orbitals

Rather than using superscripts to denote the number of electrons in each sublevel, we represent each orbital within the sublevel with a box or a line. Electrons are then depicted as arrows, either pointing upwards (↑) or downwards (↓) to indicate their spin.

Expanding the Notation

Let’s expand the portion related to the outermost shell (n=4):

• 4s²: This means the 4s sublevel is completely filled. We represent the 4s sublevel as a single box with two electrons:

  4s: ↑↓

• 3d¹⁰: This refers to the 3d sublevel, located one shell lower. It’s also completely filled with 10 electrons, spread across 5 orbitals.

  3d: ↑↓ ↑↓ ↑↓ ↑↓ ↑↓

• 4p⁴: This means the 4p sublevel contains four electrons. It requires careful consideration of Hund’s rule. We fill each of the three p orbitals with one electron first, then pair up in one orbital:

  4p: ↑↓ ↑ ↑

The Complete Visualization (Focus on Valence Shell)

While a fully expanded notation would include all orbitals, we can focus on the valence shell (outermost shell) which includes the 4s and 4p orbitals.

A condensed visualization looks like this:

4s: ↑↓ 4p: ↑↓ ↑ ↑

This representation highlights the two unpaired electrons in the 4p sublevel, which contribute to Selenium’s bonding properties. These unpaired electrons make Selenium readily able to form two covalent bonds. The filled 4s orbital is less reactive. Understanding this visual notation clarifies the role of each orbital in selenium’s chemical behavior.

So, there you have it! Hopefully, you now have a clearer picture of orbital notation for selenium. Go forth and explore the fascinating world of atomic structure!