Write the formulas for the following molecules. (a) water (b) ammonia (c) hydrazine (d) sulfur hexafluoride (e) phosphorus pentachloride

Understanding the chemical composition of substances is fundamental in chemistry. It involves identifying which chemical elements are present in a molecule and in what quantities. Take water (H₂O) for example; it is made up of two hydrogen (H) atoms and one oxygen (O) atom. This 2:1 ratio is crucial for the unique properties of water.

When analyzing the composition of ammonia (NH₃), we see that the molecule consists of one nitrogen (N) atom bonded to three hydrogen (H) atoms. This precise ratio and arrangement of nitrogen and hydrogen results in the distinct characteristics of ammonia, such as its pungent smell.

The chemical composition is not just a list of elements; it defines the number of atoms of each element in a molecule, which directly influences the chemical and physical properties of the substance.

Molecular structure refers to the three-dimensional arrangement of atoms within a molecule. It determines a molecule's geometry, which affects its reactivity and interaction with other molecules.

For instance, hydrazine (N₂H₄) has a specific molecular structure where two nitrogen atoms are bonded to each other, with each nitrogen also bonded to two hydrogen atoms. This particular arrangement impacts how hydrazine behaves chemically, including its ability to act as a reducing agent.

Sulfur hexafluoride (SF₆), on the other hand, has a sulfur atom at the center of a symmetrical octahedral shape, surrounded by six fluorine atoms. This stable configuration is what gives sulfur hexafluoride its inert qualities, making it useful as an insulating gas in the electrical industry.

Inorganic compounds, such as those listed in the exercise, are chemical compounds that typically lack carbon-hydrogen bonds. There are exceptions, but most inorganic compounds consist of a combination of elements other than carbon and hydrogen.

Phosphorus pentachloride (PCl₅) is an example of an inorganic compound, where one phosphorus (P) atom is bonded with five chlorine (Cl) atoms. Unlike organic compounds, inorganic substances can have a much broader range of chemical bonding and can include metals, salts, and minerals among others.

The study of inorganic compounds includes examining their synthesis, behavior and reactivity in various conditions, which often differ significantly from those of organic compounds due to the diversity in elemental composition and types of bonding.