Question

Why does hydrogen exist as a diatomic molecule?

Short answer

Hydrogen exists as a diatomic molecule because it shares its single electron with another hydrogen atom to achieve a stable electron configuration. This shared pair of electrons forms a covalent bond in the H2 molecule.

Step-by-step solution

Understand atomic structure and electron configuration of Hydrogen

The atomic number of hydrogen is 1, which signifies that it has only one electron in its outermost shell. The stable electron configuration of the Hydrogen atom can only be achieved when it has two electrons in its K shell as per the 2n^2 rule (where n represents shell number). In its natural state, Hydrogen has only one electron, thus it is not yet stable.

Concept of Covalent Bond and Formation of H2

Hydrogen forms a covalent bond to achieve stability. A covalent bond is a form of chemical bonding where shared electron pairs contribute to bond formation. Each Hydrogen atom shares its single electron with another Hydrogen atom forming a shared pair of electrons, i.e., a covalent bond. This results in each Hydrogen atom now having two electrons in its valence shell, resembling the electron configuration of the noble gas Helium, hence reaching stability.

Explanation of Diatomic Nature

Because every atom of hydrogen shares its 1 electron with another hydrogen atom, forming a complete shell around each hydrogen atom. This bond is very strong due to the close proximity of the shared pair of electrons to the nuclei. As a result, they exist as a diatomic molecule, H2.

Key concepts

Hydrogen Atom

Hydrogen, the simplest and most abundant element in the universe, is fundamental to numerous chemical processes. Each hydrogen atom consists of a single proton and a single electron. Because its atomic number is 1, hydrogen has only one electron located in its outermost shell. In its natural state, this electron configuration makes hydrogen unstable because it seeks to fill or share its electron to achieve a more stable electron configuration.

According to quantum mechanics, the most stable configuration for any atom's outer shell is to have two electrons, which would fill the first shell (the K shell) and mimic the stable configuration of helium. However, hydrogen naturally occurs with just one electron, making it reactive as it seeks to achieve stability by gaining one more electron.

Covalent Bonding

Covalent bonding is a critical concept in creating stable molecules from single atoms, such as hydrogen. In covalent bonds, atoms share pairs of electrons to fill their outer electron shells and achieve stability. This type of bonding is common among nonmetal atoms, which like to attain stable electron configurations similar to those of noble gases.

When two hydrogen atoms meet, each atom contributes its single electron to form a shared pair of electrons. This sharing of electrons forms a covalent bond. As a result, each hydrogen atom effectively attains two electrons in its outermost shell, achieving the electron configuration of helium, which is a noble gas. This shared electron pair is situated between the two hydrogen nuclei and acts as a strong cohesive force, resulting in the formation of a diatomic molecule, (H_2).

Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's orbitals. For hydrogen, with its single electron, the electron configuration is quite simple: 1s¹. This indicates its one electron occupies the first (and only) orbital available, making hydrogen atoms eager to either share or gain an electron to fill this shell.

In the context of a diatomic hydrogen molecule (H_2), both hydrogen atoms share their single electrons, thereby achieving a full shell of two electrons. This mirrors the electron configuration of helium, which is represented as 1s².

• Basic configuration of hydrogen in isolation: 1 electron in the 1s orbital.
• In (H_2), each hydrogen complements the other's electron to jointly occupy the 1s orbital with two electrons.

This shared approach results in a much more stable configuration, keeping the hydrogen atoms bonded together.