When this response was acknowledged, the loading process began. The parenthesis only serve as a grouping function: (CH3)3-C-represents a carbon atom to which three methyl groups are linked, whereas (CH3)3-C-represents a carbon atom in the chain to which one hydrogen atom and a methyl group are bonded.
Parentheses are frequently used in chemical equations to establish subgroups of atoms inside a molecule. The subscript outside the parenthesis in such a formula indicates that to count atoms, multiply that subscript by the number of atoms within. So, in the acetyl chloride equation above, there are 3 molecules involved, so the total number of chloride ions is 3 x 1.02 = 3.06.
Subscripts can also be used to indicate atoms that are attached to certain elements, called isotopes. For example, carbon has three stable isotopes: 12C, 13C, and 14C. Subscripts can be used to distinguish between these isotopes. In the acetyl chloride equation, the symbol "^" is used to indicate a radioactive atom. Radium has an atomic mass of 224, so its replacement rate is 1 out of every 5,920 years. Half-life is the time it takes for the amount of an element present in an object to be reduced to one-half of its original value. Radioactive decay is usually described by a half-life. For radium, the half-life is about 3,600 years.
Isotopes can be found in nature or produced in laboratories by using nuclear reactions. For example, uranium is composed of 238U but also contains some 235U and 232Th isotopes.
Here's an illustration: if there are 12 atoms in the carbon-carbon single bond, then there should be (12x1) or 24 atoms in the first subgroup; and (12x2) or 48 atoms in the second subgroup.
In general, when counting atoms inside a molecule, count each pair of electrons as two atoms because they are inseparable. A covalent bond occurs when two atoms share one pair of electrons giving them a total of eight pairs instead of the usual two. Therefore, four atoms share two electrons giving them a total of six pairs instead of the usual two. There are other factors that may influence how many atoms are in a molecule but these are the most important for understanding chemical formulas.
Subgroups also have meanings in chemistry. In this case, the term "subgroup" means a group of atoms that can be removed from the main group without changing the overall structure of the molecule. For example, if you remove both the hydrogen and oxygen atoms from water, it still remains water after removal of the hydrogens and oxygens.
So in the example below, the number of atoms in carbon monoxide is calculated as 10 × 6 = 60.
Carbon monoxide is composed of one carbon and one oxygen atom. The chemical formula for carbon monoxide is CO. Since there are two oxygen atoms in carbon monoxide, the symbol O appears twice in the formula. The single carbon atom is the sixth most abundant element in the earth's crust, so its atomic number is 6. Combining these numbers yields the formula CO, which is the same as the formula for methane. Methane is the simplest organic compound containing only one carbon atom and four hydrogen atoms. It is also the most common molecule on earth after water.
The molecular mass of carbon monoxide is not very different from that of methane: 68.09 g/mol. But because carbon monoxide contains one more oxygen atom than methane, the molecular formula of carbon monoxide is actually CO. Without the parentheses, the formula would read CH4 instead. Parentheses are important in chemistry because they can clarify whether you are using the full formula or a simplified version of it. In general, formulas with parentheses are more detailed than those without.