Question

Match the substances on the left with the basic units that compose them on the right. Remember that atomic elements are composed of atoms, molecular elements are composed of diatomic molecules, molecular compounds are composed of molecules, and ionic compounds are composed of formula units. \(\begin{array}{ll}\mathrm{NI}_{3} & \text { molecules } \\ \text { copper metal } & \text { single atoms } \\ \mathrm{SrCl}_{2} & \text { diatomic molecules } \\ \text { nitrogen } & \text { formula units }\end{array}\)

Short answer

NI3 is made up of molecules, copper metal of single atoms, SrCl2 of formula units, and nitrogen of diatomic molecules.

Step-by-step solution

Identify the Types of Each Substance

Firstly, identify what each substance on the left side of the list is: - NI3 (Nitrogen triiodide) is a molecular compound.- Copper metal is an atomic element.- SrCl2 (Strontium chloride) is an ionic compound.- Nitrogen gas (often referred to simply as nitrogen) found in nature is a molecular element as it exists as N2.

Match the Substances with Their Basic Units

Once the substance types are identified, match them with their basic units based on the definitions given in the problem statement:- NI3, as a molecular compound, is composed of molecules.- Copper metal, as an atomic element, is composed of single atoms.- SrCl2, as an ionic compound, is composed of formula units.- Nitrogen, as a molecular element, is composed of diatomic molecules.

Correct the Given Matches

Using the matches identified in the second step, correct the associations made between substances and basic units:- NI3 should be matched with 'molecules'.- Copper metal should be matched with 'single atoms'.- SrCl2 should be matched with 'formula units'.- Nitrogen should be matched with 'diatomic molecules'.

Key concepts

Molecular Compounds

A molecular compound consists of molecules formed by the covalent bonding of atoms. In covalent bonds, atoms share electrons to achieve a full outer shell, which is the driving force behind the formation of most molecular compounds. Examples of molecular compounds are water (H₂O) and carbon dioxide (CO₂).

A key characteristic of molecular compounds is that they can be composed of multiple types of atoms, like nitrogen triiodide (NI₃) from the exercise. These atoms come together in specific ratios to form the compound's unique molecule, with its own physical and chemical properties. These properties differ from those of the atoms and elements that comprise it.

Atomic Elements

Atomic elements are substances that are made up entirely of one type of atom. These are the basic building blocks of matter and are listed on the periodic table of elements. Each element has atoms with a specific number of protons in their nucleus, like the copper (Cu) mentioned in the exercise.

Atomic elements do not bond with other atoms in their basic form and are found as individual, or single, atoms. They retain all their elemental properties. Elements like copper can further join together in a repeating, orderly fashion to form a metal with its characteristic malleability, conductivity, and luster.

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons to or from one another, leading to the creation of positively and negatively charged ions. This electron exchange often occurs between metals and nonmetals. An ionic bond is the electrostatic force that holds these oppositely charged ions together in a lattice structure, known as a formula unit.

An example of an ionic compound is strontium chloride (SrCl₂), as indicated in the exercise. Ionic compounds have high melting and boiling points and typically dissolve in water to form conductive solutions. The formula unit is the simplest ratio of the ions present in the compound that maintains electrical neutrality.

Diatomic Molecules

Diatomic molecules are a specific type of molecular compound consisting of only two atoms, which can be either the same or different elements. The 'di-' prefix means two, and thus diatomic molecules always contain two atoms. For instance, nitrogen gas (N₂) is made up of two nitrogen atoms bonded together, as highlighted in the exercise.

Seven elements naturally exist in a diatomic state: hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), chlorine (Cl₂), bromine (Br₂), and iodine (I₂). These molecules are stable and commonly found in nature due to the strong bond that forms between the two atoms, which is typically a covalent bond.