Fill in the blank.
The name of the covalent compound N2O5 is
Molecular Formulas and Structural Formulas
Most covalent substances exist in the form of individual molecules. For these substances, the chemical formula is also referred to as its molecular formula. In other words, a molecular formula is the chemical formula of a compound that exists in the form of individual molecules. The molecular formula specifies the number of elements present in one molecule of a molecular compound. For example, the element oxygen exists in nature as a molecule of two covalently bonded oxygen atoms. The molecular formula for oxygen gas is O2. Another example is methane with molecular formula CH4. Each molecule of methane contains one carbon atom covalently bonded to four hydrogen atoms.
Network solids contain covalent bonds, but they are not molecular in structure. Therefore, network solids do not have molecular formulas; they only have chemical formulas. The same is true for ionic compounds, which do not consist of individual molecules but are rather composed of lattice arrangements of ions. The simplest ratio of ions in an ionic compound gives its chemical formula.
Chemists attempt to draw representations of molecules. In their drawings,they represent each atom by its symbol and represent the bond between two atoms by a straight line: ‘______’. Following this method, you can write H − H to represent a molecule of hydrogen, H2. A representation of a molecule showing the atoms and how they are bonded together is called a structural formula. A structural formula shows not only the number of atoms of each kind that are present in a molecule but also how the atoms are bonded together.
The structural formula for methane shows a drawing of one carbon atom connected by four straight lines to four hydrogen atoms. Each straight line represents a covalent bond formed by a pair of electrons.
If you are given the molecular formula for a compound, you can often use it to create its structural formula. For many compounds, especially smaller ones, there is only one way to arrange the atoms and connecting bonds to create a structural formula from the molecular formula. For other compounds, it may be possible to draw two or more different structural formulas for one molecular formula. For example, the molecular formula C2H6O may have two different structural formulas, as shown in Figure 37. One structural formula represents the compound ethanol, and the other structural formula represents the compound dimethyl ether. These are different compounds that have the same molecular formula and different structural formulas.
Figure 37 Ethanol and dimethyl ether have the same molecular formula, C2H6O,
but are different compounds because they have different structural formulas.
but are different compounds because they have different structural formulas.
What information is given by structural formulas but not by molecular formulas?
the mass of the molecule
the smallest ratio of elements composing the molecule
the arrangement of atoms in the molecule
the number of atoms of each element in a molecule
the elements composing the molecule
answer :
the arrangement of atoms in the molecule
|
| Response: That's the correct answer Empirical Formulas
When you know the molecular formula of a compound, you know exactly how many atoms of each element are present in one molecule of that compound. You also know the ratios of atoms of the elements present in the compound. Consider the molecular formula N2O4. This molecule contains a total of six atoms—two nitrogen and four oxygen atoms. The ratio of nitrogen to oxygen is 2 to 4, or more simply 1 to 2. There are twice as many oxygen atoms as nitrogen atoms.
In cases like N2O4, we can write an empirical formula, also known as simplest formula, that shows the simplest ratio of elements in the compound. The empirical formula for N2O4 is NO2.
The table below lists both the molecular and empirical formulas for several covalent compounds. Notice that in some cases the molecular and empirical formulas are the same.
For ionic compounds, the empirical formula is always the same as the chemical formula of the compound. This is because the chemical formula represents the simplest ratio of elements in the compound.
Match each expression with what best defines its function.
shows the simplest ratio of elements in the compound, it is also known as simplest formula
shows the number and kind of atoms present in a molecule but does not show how the atoms are bonded together
is a representation of a molecule showing the atoms and how they are bonded together
|
shows the simplest ratio of elements in the compound, it is also known as simplest formula
shows the number and kind of atoms present in a molecule but does not show how the atoms are bonded together
= molecular formula
is a representation of a molecule showing the atoms and how they are bonded together
= structural formula | ||
| Response: That's the correct answer
What information about a covalent compound is inferred from its molecular formula but not from its empirical formula?
the smallest ratio of elements composing the molecule
the arrangement of atoms in the molecule
the elements composing the molecule
the mass of the molecule
the number of atoms of each element in a molecule
answer :
|
