Question

What is the relationship between the electron configuration of an element and the period in which that element appears in the periodic table?

Short answer

The period number of an element corresponds to the highest principal quantum number (n) in its electron configuration.

Step-by-step solution

Understand Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It is typically written using numbers and letters to represent energy levels, subshells, and number of electrons in each subshell (e.g., 1s^2 2s^2 2p^6).

Identify Periods in the Periodic Table

A period in the periodic table is a horizontal row. Elements in the same period have the same number of atomic orbitals. For example, elements in Period 1 have electrons only in the 1s orbital, while elements in Period 2 have electrons in the 1s, 2s, and 2p orbitals.

Determine Relationships Between Electron Configuration and Period

An element's period in the periodic table corresponds to the highest principal quantum number (n) in its electron configuration. For instance, if the highest energy level occupied by electrons is the third shell (n=3), the element is in Period 3.

Examples for Clarification

For example, the electron configuration of sodium (Na) is 1s^2 2s^2 2p^6 3s^1. The highest principal quantum number (n=3) indicates that sodium is in Period 3. Similarly, chlorine (Cl) has an electron configuration of 1s^2 2s^2 2p^6 3s^2 3p^5, placing it in Period 3 as well.

General Conclusion

Based on the above steps, it can be concluded that the period number of an element corresponds to the highest principal quantum number (n) in its electron configuration.

Key concepts

electron configuration

Electron configuration is a way of describing the arrangement of electrons within an atom.
Each electron is located in an energy level, or shell, which is defined by its distance from the nucleus.
These energy levels are further divided into subshells, such as s, p, d, and f.
The electron configuration notation indicates how many electrons are in each subshell.
For example, the configuration 1s^2 2s^2 2p^6 means there are two electrons in the 1s subshell, two in the 2s subshell, and six in the 2p subshell.
Understanding electron configuration helps us predict an element's chemical properties and behavior. It tells us about the energy and position of each electron in an atom, forming the basis for understanding many principles in chemistry.

periodic table

The periodic table is a chart that organizes all known elements by their atomic number, electron configurations, and recurring chemical properties.
Each horizontal row on the periodic table is called a period.
Elements in the same period have the same number of atomic orbitals. For example, Period 1 includes hydrogen and helium, which only have electrons in their 1s subshell.
As you move to higher periods, there are more orbitals to fill, such as 2s, 2p, 3s, etc.
The periodic table helps us quickly locate elements and understand their characteristics based on their position, making it a valuable tool in chemistry.

principal quantum number

The principal quantum number, denoted as n, is a number that signifies the main energy level, or shell, occupied by electrons in an atom.
It is one of four quantum numbers used to describe the unique quantum state of an electron.
The principal quantum number starts at 1 and increases, with higher numbers indicating electrons that are further from the nucleus and have higher energy.
For example, in the electron configuration 1s^2 2s^2 2p^6, the principal quantum number for the first shell is 1, while for the second shell it is 2.
The period to which an element belongs on the periodic table corresponds directly to the highest principal quantum number of its electrons.
Therefore, understanding this relationship helps in predicting the placement of elements and explaining periodic trends in a structured way.