Question

What is the outermost orbital of elements in the third period? A. \(s\)-orbital B. \(p\)-orbital C. \(d\)-orbital D. \(f\)-orbital

Short answer

B. p-orbital

Step-by-step solution

Identify the Period

Determine which period the elements belong to. In this case, it’s stated in the problem: the third period.

Understand Orbital Filling Order

Review how orbitals are filled based on the Aufbau principle. The third period involves filling the 3s, 3p, and possibly the 3d orbitals.

Recognize the Outermost Orbital for Third-Period Elements

Identify which orbitals are the outermost for elements in the third period. Elements in the third period fill the 3s and 3p orbitals. The 3p orbital is higher in energy and thus is the outermost orbital for these elements.

Choose the Correct Option

Select the option that corresponds to the outermost orbital of third-period elements. Given the choices, the 3p orbital is the correct answer.

Key concepts

Aufbau principle

The Aufbau principle is a key concept in understanding how electrons are arranged in an atom. 'Aufbau' is a German word meaning 'building up' or 'construction'. According to this principle, electrons fill atomic orbitals in a specific order, starting from the lowest energy level and moving to higher ones. This means that the 1s orbital fills first, followed by the 2s, the 2p, and so on. This order of filling is essential to grasp because it explains the arrangement of electrons in any given element. For third-period elements, this principle dictates that their electrons fill the 3s and 3p orbitals successively.

orbital filling order

To understand the arrangement of electrons in atoms, it's crucial to know the orbital filling order. This order follows a predictable pattern defined by the Aufbau principle. The sequence of filling for the first three periods is as follows:

• 1s
• 2s
• 2p
• 3s
• 3p

The '3d' orbital does not come into play until the fourth period and higher energy levels. For third-period elements, the electrons fill the 3s orbital first, followed by the 3p orbital. This understanding shapes how we identify the outermost orbital for any element within these periods.

outermost orbital

For atoms, the 'outermost orbital' represents the highest energy level that contains electrons. For third-period elements, identifying this orbital involves understanding which orbitals get filled.
The electron configuration for third-period elements involves filling the 3s and then the 3p orbitals. Thus, the outermost orbital for these elements is the 3p orbital because it is at a higher energy level compared to the 3s. By recognizing the outermost orbital, we can predict an element’s chemical behavior and reactivity, as these outer electrons are usually involved in bonding.