Question

Explain why the gaseous nonmetals exist as diatomic molecules, but other gaseous elements exist as single atoms. (Chapter 8)

Short answer

Gaseous nonmetals exist as diatomic molecules due to their high electronegativity and/or ionization energies, leading them to form covalent bonds with other atoms of the same element to achieve stable electron configurations and minimize potential energy. In contrast, other gaseous elements, like noble gases, exist as single atoms because they already possess full or stable outer electron configurations, and their low electronegativity and ionization energies make them reluctant to form bonds with other atoms.

Step-by-step solution

Definition of diatomic molecules

Diatomic molecules are molecules composed of two atoms, usually of the same element, bonded together. Examples of such molecules include hydrogen (H2), oxygen (O2), and nitrogen (N2).

Properties of gaseous nonmetals

Gaseous nonmetals like hydrogen (H2), oxygen (O2), and nitrogen (N2) have high electronegativity and/or ionization energies. These properties result in their tendency to form covalent bonds with other atoms of the same element to achieve stable electron configurations and lower potential energy. In diatomic nonmetal molecules, each atom shares its valence electrons with the other atom to achieve a full or more stable outer electron shell.

Properties of other gaseous elements

Elements that exist as single atoms in the gas phase, such as noble gases (helium, neon, argon, etc.), have full or stable electron configurations in their outermost energy levels. These elements have low electronegativity and ionization energies, making them reluctant to form bonds with other atoms.

Comparison and explanation

Gaseous nonmetals form diatomic molecules due to their high electronegativity and/or ionization energies, which drive them to form covalent bonds with other atoms of the same element in order to achieve stable electron configurations and minimize potential energy. On the other hand, other gaseous elements, such as noble gases, exist as single atoms in the gas phase because they already possess full or stable electron configurations in their outer energy levels and their low electronegativity and ionization energies make them reluctant to form bonds with other atoms.

Key concepts

Electronegativity

Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself. It is a critical concept in chemistry because it helps explain why certain elements form bonds more readily than others. As you delve into the world of diatomic molecules like hydrogen (H2), oxygen (O2), and nitrogen (N2), you encounter their high electronegativity, a feature that fundamentally influences their behavior.

Atoms with high electronegativity, such as the nonmetals mentioned, do not prefer to exist on their own; instead, they seek out other atoms to bond with. This desire to bond is due to their effort to attain a more stable electronic configuration. In a diatomic molecule, the two atoms contribute their valence electrons to form a cooperative bond, sharing the electrons to satisfy both atoms' need for a complete outer shell.

Covalent Bonds

Covalent bonds are the glue that holds together atoms in diatomic molecules. This type of bond involves the sharing of electron pairs between atoms, enabling them to achieve greater stability. In diatomic molecules, each atom shares one or more pairs of valence electrons with its partner, leading to the formation of a stable molecule.

For example, when two oxygen atoms form O2, they share two pairs of electrons, resulting in a double bond that provides the full octet each atom desires. The stability that arises from covalent bonding in gaseous nonmetals illustrates an essential principle in chemistry: atoms form bonds to decrease their potential energy and increase their stability. Covalent bonds, therefore—particularly in gaseous nonmetals—reflect the pursuit of the lowest possible energy state and maximum stability.

Electron Configurations

The electron configuration of an atom describes the distribution of electrons in its atomic orbitals. For gaseous nonmetals, these configurations contain unfilled valence shells, which lead to an innate desire to achieve a more stable, filled valence shell, often seen in the noble gas configuration.

In the context of diatomic molecules, the sharing of electrons allows each atom to pretend, in a sense, that they have filled their outermost shells, thereby achieving pseudo-noble gas configurations. This electron sharing, intrinsic to covalent bonding, is a harmonious dance, fulfilling the octet rule for each participant in these diatomic pairings. Through this sharing mechanism, gaseous nonmetals reach a more stable and energetically favorable state, differing significantly from noble gases, whose naturally complete electron configurations make them more chemically inert.

Gaseous Nonmetals

Gaseous nonmetals such as hydrogen, oxygen, and nitrogen uniquely exist as diatomic molecules due to their physical and chemical properties. They are characterized by high electronegativity and a strong drive for electron sharing that promotes their existence in pairs rather than as isolated atoms.

One way to conceptualize this is by thinking of them as socially inclined atoms, preferring to 'pair up' rather than go solo. The formation of diatomic molecules lowers the potential energy of the atoms involved, which is nature's way of favoring stability. This partnering-up stands in stark contrast to gaseous elements like noble gases, which are more like solitary figures, completely content with their full valence shells and thus have no inherent need to form bonds with others.