Question

Determine the number of each type of atom in each of the following chemical formulas: a. \(\mathrm{Na}_{2} \mathrm{O}\) b. \(\mathrm{CF}_{2} \mathrm{Cl}_{2}\) c. \(\mathrm{K}_{2} \mathrm{CO}_{3}\) d. \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\)

Short answer

a. 2 sodium, 1 oxygen b. 1 carbon, 2 fluorine, 2 chlorine c. 2 potassium, 1 carbon, 3 oxygen d. 1 magnesium, 2 hydrogen, 2 carbon, 6 oxygen

Step-by-step solution

Identify the Atoms in Sodium Oxide

For the chemical formula \(\mathrm{Na}_{2} \mathrm{O}\), identify the types of atoms present. There are sodium atoms (Na) and oxygen atoms (O).

Count the Atoms in Sodium Oxide

Count the number of each atom in \(\mathrm{Na}_{2} \mathrm{O}\). There are two sodium atoms and one oxygen atom, as indicated by the subscript numbers.

Identify the Atoms in Carbon Difluoride Dichloride

For the chemical formula \(\mathrm{CF}_{2} \mathrm{Cl}_{2}\), identify the types of atoms present. There are carbon atoms (C), fluorine atoms (F), and chlorine atoms (Cl).

Count the Atoms in Carbon Difluoride Dichloride

Count the number of each atom in \(\mathrm{CF}_{2} \mathrm{Cl}_{2}\). There is one carbon atom, two fluorine atoms, and two chlorine atoms.

Identify the Atoms in Potassium Carbonate

For the chemical formula \(\mathrm{K}_{2} \mathrm{CO}_{3}\), identify the types of atoms present. There are potassium atoms (K), carbon atoms (C), and oxygen atoms (O).

Count the Atoms in Potassium Carbonate

Count the number of each atom in \(\mathrm{K}_{2} \mathrm{CO}_{3}\). There are two potassium atoms, one carbon atom, and three oxygen atoms.

Identify the Atoms in Magnesium Bicarbonate

For the chemical formula \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\), identify the types of atoms present. There are magnesium atoms (Mg), hydrogen atoms (H), carbon atoms (C), and oxygen atoms (O).

Count the Atoms in Magnesium Bicarbonate

Count the number of each atom in \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\). There is one magnesium atom, two hydrogen atoms (since there are two \(\mathrm{HCO}_{3}\) groups, each containing one hydrogen), two carbon atoms, and six oxygen atoms (since each \(\mathrm{HCO}_{3}\) group contains three oxygen atoms).

Key concepts

Counting Atoms in Compounds

Understanding the basics of counting atoms in chemical compounds is fundamental in chemistry. Atoms are the building blocks of matter, and the way they combine to form compounds is described by chemical formulas. These formulas use subscript numbers to indicate the number of each type of atom present in the compound. For example, in the compound Na2O, the subscript '2' after sodium (Na) shows there are two sodium atoms. If no subscript follows an element symbol, such as oxygen (O) in this case, it means there is one atom of that element in the compound.

Let's take Mg(HCO3)2 as an example on how to count atoms when a compound includes a polyatomic ion, which is a group of atoms that behave as a single unit. Here, the polyatomic ion HCO3 is enclosed in parentheses, with a subscript '2' outside, indicating there are two such groups in the compound. To determine the total number of each type of atom, multiply the number of atoms in each polyatomic ion by the subscript outside the parentheses. This leads to two hydrogen atoms, two carbon atoms, and six oxygen atoms in total.

Chemical Notation

Chemical notation is the shorthand that chemists use to convey detailed information about the composition of molecules and compounds succinctly. It includes the use of element symbols from the periodic table, such as 'K' for potassium or 'C' for carbon. Moreover, it employs subscript numbers to indicate the number of atoms of each element in the compound and parentheses to group certain atoms together, normally used for polyatomic ions or molecules that are part of a larger complex.

An understanding of chemical notation is crucial for not only counting atoms but also for visualizing the structure of a compound. For instance, in CF2Cl2, we understand that each fluorine (F) and chlorine (Cl) is bonded to the carbon (C) atom individually. Chemical notation also guides us in balancing chemical equations, since the notations must be equal on both sides of the reaction in accordance with the law of conservation of mass.

Molecular Composition

The molecular composition of a compound tells us what atoms are present and in what amounts. Each compound has a unique molecular formula that provides this information, often resulting in diverse physical and chemical properties. For example, the molecular composition of K2CO3 indicates that there are two potassium atoms, one carbon atom, and three oxygen atoms within one molecule of potassium carbonate.

The molecular composition determines the compound's properties, such as its reactivity, color, and physical state at room temperature. In more complex molecules, other factors such as the arrangement of the atoms and the types of bonds between them will also significantly affect these properties. Studying molecular composition is essential for predicting and understanding reactions that the compound may undergo.

Stoichiometry Basics

Stoichiometry is a section of chemistry that involves the calculations of the reactants and products in chemical reactions. It is based on the law of conservation of mass where the total mass of reactants is equal to the total mass of products. The stoichiometric coefficients in a balanced chemical equation tell us the ratio of how many molecules or moles of each substance are involved.

When performing stoichiometric calculations, we use the chemical formula to understand the molar ratio between the reactants and products. For example, to react sodium oxide (Na2O), with water to form sodium hydroxide, we need to know the exact amount of each substance to use. Knowing how to count atoms and understand their arrangement through chemical notation is critical in mastering the basics of stoichiometry, which in turn is key to predicting the amount of product produced or reactant needed in a given chemical reaction.