Question

Give the electron configurations for the following atoms. Do not use the noble gas notation. Write out the complete electron configuration.

Short answer

The electron configurations for the given atoms are as follows: Hydrogen (H): \(1s^1\) Helium (He): \(1s^2\) Lithium (Li): \(1s^2 2s^1\)

Step-by-step solution

Electron Configuration for Hydrogen (H)

The atomic number of Hydrogen is 1. This means that there is one electron in a hydrogen atom. The electron configuration for Hydrogen is: \(1s^1\) which represents that there is one electron in the 's' orbital of the first energy level.

Electron Configuration for Helium (He)

The atomic number of Helium is 2. This means that there are two electrons in a helium atom. The electron configuration for Helium is: \(1s^2\) which represents that there are two electrons in the 's' orbital of the first energy level.

Electron Configuration for Lithium (Li)

The atomic number of Lithium is 3. This means that there are three electrons in a lithium atom. The electron configuration for Lithium is: \(1s^2 2s^1\) which represents that there are two electrons in the 's' orbital of the first energy level, and one electron in the 's' orbital of the second energy level.

Key concepts

Atomic Number

The atomic number is a fundamental concept in chemistry and physics. It uniquely identifies each chemical element and is equivalent to the number of protons found in the nucleus of an atom. This number not only determines the element's position in the periodic table but also provides essential information about the electronic structure of the atom.

For example, hydrogen has an atomic number of 1, which means it has one proton and, in a neutral atom, one electron. Helium, on the other hand, has an atomic number of 2, therefore it has two protons and two electrons. Understanding the atomic number of an element allows us to predict its chemical and physical properties by applying the principles of electron configurations.

Energy Levels

Energy levels, also known as electron shells, are defined regions around the nucleus of an atom where electrons are likely to be found. These shells are organized in order of increasing energy, with each level capable of holding a certain maximum number of electrons. For instance, the first energy level can hold up to 2 electrons, while the second can hold up to 8.

When determining electron configurations, electrons will fill the lowest energy levels first before moving to higher levels, following the Aufbau principle. This principle is the key to understanding why the electron configuration for Hydrogen is written as 1s¹, with the electron occupying the first and lowest energy level.

Electron Orbital

An electron orbital is a three-dimensional space within an energy level where there is a high probability of finding an electron. Orbitals are categorized into different types, namely s, p, d, and f, each with a distinct shape and capacity to hold a certain number of electrons.

The 's' orbital is spherical and can contain up to two electrons, which explains why the electron configuration for Helium is written as 1s². As atoms increase in atomic number, electrons begin to occupy not just 's' orbitals but also 'p', 'd', and 'f' orbitals. Each new electron occupies the lowest energy orbital available, filling these orbitals in a specific order to minimize the atom’s energy.