Question

cdcl₂ ca(oh)₂ cobalt k₂cro₄ oxygen cocl₂ h₂ ni helium chlorine so₂ c₂h₆ single atoms diatomic molecules molecules formula units

Explanation:

• Single atoms: Elements that exist as individual atoms. Cobalt (Co), Nickel (Ni), and Helium (He) are single - atom substances. Cobalt and Nickel are metals that typically exist as single atoms in their elemental form, and Helium is a noble gas which also exists as single atoms.
• Diatomic molecules: Molecules composed of two atoms. Oxygen (\(O_2\)) and Chlorine (\(Cl_2\)) are diatomic molecules. The standard form of oxygen gas is \(O_2\) and chlorine gas is \(Cl_2\).
• Molecules: Compounds or elements (in non - single - atom, non - diatomic form) composed of multiple atoms. \(H_2\) (dihydrogen, can be considered a simple molecule), \(SO_2\) (sulfur dioxide), and \(C_2H_6\) (ethane) are molecules. \(H_2\) is a simple molecular form of hydrogen, \(SO_2\) has one sulfur and two oxygen atoms, and \(C_2H_6\) has two carbon and six hydrogen atoms.
• Formula units: The empirical formula of an ionic or covalent network solid compound. \(CdCl_2\) (cadmium chloride), \(Ca(OH)_2\) (calcium hydroxide), and \(K_2CrO_4\) (potassium chromate) are formula units. These are ionic compounds, and their formulae represent the ratio of ions in the compound.

Answer:

• Single atoms: Cobalt, Ni, Helium
• Diatomic molecules: Oxygen, Chlorine
• Molecules: \(H_2\), \(SO_2\), \(C_2H_6\)
• Formula units: \(CdCl_2\), \(Ca(OH)_2\), \(K_2CrO_4\)