In this post, I will focus mainly on discussing molecular substances. First, I will start by briefly introducing a concept that we be recurring: that is, chemical formulas. A chemical formula is actually a representation of the relative proportions of atoms of different elements in a substance, represented by numerical subscripts, of an atom, which is represented by its atomic symbol as on the periodic table of elements (Ebbing and Gammon 2009).
An example of a chemical formula is Al2O3, which represents the compound aluminum oxide. The information that this particular chemical formula conveys is that aluminum atoms and oxygen atoms make up the compound, at a ratio of 2:3, respectively. NaCl is another chemical formula. You may notice with some substances, like NaCl, some elements are not followed by a subscript of a number. When this is the case, it means that the subscript “1” is actually implied. So, in this case, both sodium and chlorine have an implied subscript of “1.” So, the compound sodium chloride consists of sodium and chlorine atoms in a 1:1 ratio (wherein there are an equal number of atoms of each of the elements in it) (Ebbing and Gammon).
Moving on to the concept of molecular substances. Something that we’ve talked a lot about but have perhaps not explicitly defined yet is the molecule. A molecule consists of a group of atoms that are held together by powerful attractive forces, called chemical bonds. In a molecular substance, all of the molecules that comprise it are alike. Molecules are extremely minuscule, and because of their size, even a small sample of a molecular substance may contain trillions of molecules, which is literal in the case of water, wherein a billionth of a drop of it contains approximately two trillion water molecules (Ebbing and Gammon 2009).
Distinct from a chemical formula is a molecular formula. A molecular formula, rather than give relative proportions of atoms of different elements of a substance, gives the exact number of the different atoms of an element that make up a molecule. Hydrogen peroxide, for example, contains two atoms of hydrogen and two atoms of oxygen, with a molecular formula of H2O2. Other examples of molecular formulas are ammonia or NH3, carbon dioxide or CO2 water or H2O, and ethanol of C2H6O (Ebbing and Gammon 2009).
In molecules, I mentioned that atoms are held together tightly by powerful attractive forces. It is important to know, also, that the way that these atoms are arranged is not random. Soon, you will begin to see structural formulas, which show how atoms are bonded to one another. As a very simple example, H—O—H is the structural formula for water, with the lines joining H to O and O to H representing the chemical bonding arrangement of atoms. Structural formulas can be shortened in writing, depending upon the level of intricacy you would like to convey; as an example, ethanol can be written as CH3CH2OH, or it can be written as C2H5OH. The connectivities of atoms in a molecule are most certainly definite, and so are the spatial arrangements of atoms in a molecule (Ebbing and Gammon 2009).
Some elements by themselves are molecular substances, and can be represented by molecular formulas, such as Cl2. Each molecule of chlorine consists of two chlorine atoms that are bonded together. Sulfur has a molecular formula of S8 and is composed of eight sulfur atoms bound together. For some noble gases, such as helium and neon, their molecular formulas are merely He and Ne, because they are isolated atoms. Some atoms do not have one simple molecular structure. An example is carbon, where an indefinite number of atoms can be bonded together, and will be represented by their atomic symbols. Buckminsterfullerene is an exception to this, and it was discovered in 1985; it has the molecular formula C60 (Ebbing and Gammon 2009).
As discussed in some posts under the topic of biology, a monomer is a small molecule that serves as a precursor to a polymer, which is a very large molecule that is comprised of smaller molecules that are connected to one another repeatedly. A certain polymer is created according to the type of monomers being linked together, as well as the pattern of linkage of the monomers (Ebbing and Gammon 2009).
Both natural and synthetic polymers exist. Many of the items we use in everyday life are composed of polymers. For instance, hard plastic sofa bottles are created using two different monomers, linked in an alternating pattern. Even the Teflon® coating that is on nonstick cookware is a polymer, created by linking CF2CF2 monomers. A complete list of polymers will not be discussed here, but these are just a few examples of polymers, from which you might accurately predict that polymers are important for use in our everyday lives, in a wide range of applications (Ebbing and Gammon 2009).
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