In which period and group does an electron first appear in an \(f\) orbital?

Understanding electron configuration is crucial in the world of chemistry and quantum mechanics. It details how electrons are distributed in orbitals, subshells, and shells around an atom's nucleus. Electrons are arranged in energy levels or shells, each with subshells labeled as s, p, d, and f. The f subshell, which is our focus, has seven orbitals, each capable of holding two electrons, for a total of up to 14 electrons.

When addressing electron configurations, it is important, to begin with the lowest energy level, filling each subshell according to the Aufbau principle. Hund's rule and the Pauli exclusion principle also play a role in determining how electrons fill these orbitals. Understanding this fundamental concept allows students to predict an element's chemical properties and place it correctly within the framework of the periodic table.

The lanthanide series contains a set of 15 metallic elements, from lanthanum (La) to lutetium (Lu), occupying atomic numbers 57 through 71. These elements, often called lanthanoids or rare earth elements, are noteworthy for their similar properties, including their reactivity and the way they exhibit 'lanthanide contraction'.

This series marks the introduction of f orbitals in the electron configurations of elements. They have significant importance in various industries, ranging from electronics to energy solutions. A common characteristic of the lanthanide series is that the 4f orbitals are being populated with electrons as we progress through the series.

The periodic table is organized into rows known as periods that run from left to right. These periods are crucial in understanding the organization of the elements and their properties. For instance, all elements in a given period have the same number of atomic orbitals. In relation to the exercise, we focus on period 6, which is the first period where f orbitals start to get filled, specifically starting with the element cerium (Ce).

This period includes a mix of very diverse elements, ranging from transition metals to the inner transition metals of the lanthanide series. Periods in the periodic table help categorize elements into groups with similar chemical behavior due to their shared electron configurations.

The atomic number of an element is a fundamental property that represents the number of protons found in the nucleus of an atom. It is denoted with the symbol Z and uniquely identifies each element. The atomic number determines the position of an element in the periodic table since the elements are ordered by increasing atomic number.

In the context of our exercise, the atomic number is pivotal when we look at the f orbitals first beginning to occupy electrons. With cerium, the atomic number is 58, and it signals the onset of electron occupation in f orbitals within the lanthanide series. Understanding atomic numbers allows students to navigate the periodic table and comprehend the patterns in electron configuration among elements.