Question

Determine the number of each type of atom in each formula. (a) \(\mathrm{NH}_{4} \mathrm{Cl}\) (b) \(\mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2}\) (c) \(\mathrm{NaCN}\) (d) \(\mathrm{Ba}\left(\mathrm{HCO}_{3}\right)_{2}\)

Short answer

For (a) 1 nitrogen, 4 hydrogen, 1 chlorine. For (b) 3 magnesium, 2 phosphorus, 8 oxygen. For (c) 1 sodium, 1 carbon, 1 nitrogen. For (d) 1 barium, 2 hydrogen, 2 carbon, 6 oxygen.

Step-by-step solution

Analyze the Formula for Ammonium Chloride

Begin by examining the chemical formula \(\mathrm{NH}_{4} \mathrm{Cl}\). The subscript after the nitrogen (N) indicates there is one nitrogen atom. The subscript 4 after the hydrogen (H) indicates there are four hydrogen atoms. There is no subscript after chlorine (Cl), implying there is one chlorine atom.

Analyze the Formula for Magnesium Phosphate

Examine the chemical formula \(\mathrm{Mg}_{3}(\mathrm{PO}_{4})_{2}\). The subscript 3 indicates there are three magnesium (Mg) atoms. Since the \(\mathrm{PO}_{4}\) group is in parentheses with a subscript of 2, this means there are two phosphate groups. In each phosphate group, there is one phosphorus (P) atom and four oxygen (O) atoms. Therefore, in total, there are 2 phosphorus atoms and 2*4=8 oxygen atoms.

Analyze the Formula for Sodium Cyanide

Look at the chemical formula \(\mathrm{NaCN}\). There is one sodium (Na) atom, one carbon (C) atom, and one nitrogen (N) atom, since there are no subscripts next to these elements.

Analyze the Formula for Barium Bicarbonate

Inspect the chemical formula \(\mathrm{Ba}(\mathrm{HCO}_{3})_{2}\). There is one barium (Ba) atom. Since the \(\mathrm{HCO}_{3}\) group has a subscript of 2, there are two such groups. Each group contains one hydrogen (H), one carbon (C), and three oxygen (O) atoms. Therefore, in total, there are 2 hydrogen atoms, 2 carbon atoms, and 2*3=6 oxygen atoms.

Key concepts

Molecular Composition

Understanding the molecular composition of chemical substances is a fundamental aspect of chemistry. It involves identifying and counting the atoms of each element that make up a molecule. The molecular composition is determined by the chemical formula, which serves as a shorthand to convey information about the types of atoms present and their relative quantities.

For example, water (H₂O) consists of two hydrogen atoms and one oxygen atom. Analyzing molecular composition is essential for various applications, such as determining the properties of the substance, its reactivity, and its role in chemical reactions. When students grasp how to interpret these formulas, they can predict how molecules will interact, synthesize compounds, and understand complex reactions in organic and inorganic chemistry.

Subscripts in Chemistry

Subscripts in chemistry are small numbers located at the lower right of chemical symbols within a formula. They are used to indicate the number of atoms of the element directly before the subscript in the chemical compound. When there is no subscript written, it is implied that there is only one atom of that element.

For instance, in carbon dioxide (CO₂), the subscript '2' indicates that there are two atoms of oxygen for each atom of carbon. Understanding subscripts is imperative for correctly interpreting chemical formulas, as they determine the ratio of elements in the compound and help in balancing chemical equations. When working with polyatomic ions or groups of atoms within a formula, parentheses are combined with subscripts to denote multiple copies of the group, such as in calcium carbonate (CaCO₃) or ammonium sulfate ((NH₄)₂SO₄).

Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more different elements in definite proportions by weight, held together by chemical bonds. Compounds have unique properties that are distinct from the elements that form them. They can be categorized broadly into ionic compounds, which consist of charged ions, and molecular compounds, where atoms share electrons.

In our exercise examples, NH₄Cl (ammonium chloride) is an ionic compound, while C₆H₁₂O₆ (glucose) is a molecular compound. Knowing the type of compound is crucial for predicting the kind of reactions it may undergo and the products that will result from those reactions. Recognizing and being able to analyze chemical compounds' structures is therefore an essential skill for students mastering chemistry.