Skip to main content

How do you determine the correct subscripts in a chemical formula? What is a subscript?

Chemical formulas are a way of expressing the chemical ingredients of a compound or molecule. Molecules are made up of one or more of the same elements. The abbreviations for these elements come from the periodic table, so you should keep the periodic table handy to help you identify them. The subscripts in a chemical formula are the small numbers that you may see written in the formula. These subscripts indicate the number of atoms of each given element that are contained in the compound. 


Consider a very common chemical compound, water. The chemical formula for water is `H_2 O`.


In the chemical formula for water, the subscript for hydrogen is 2. Notice that the 2 is smaller and written slightly below the H and O. It is called a subscript because it is written ("script") "below" ("sub") the preceding letter.


The subscript 2 simply indicates that the chemical compound water has two atoms of hydrogen (elemental symbol "H"). The compound water also contains one atom of oxygen, which is indicated by an O with no subscript. If an element has no subscripts at all, you can assume that there is only one of each atom in the molecule. Consider the compound `CO`, also known as carbon monoxide. Carbon monoxide is made up of one atom of carbon (C) and one oxygen (O). 


A more complicated chemical formula can be found for the compound ammonium sulfate. It looks like this:


`(NH_4)_2 SO_4`


The parentheses group the atoms together. The subscript 2 after the parentheses means that ammonium sulfate consists of two ammonium molecules (`NH_4`), each of which is made up of one nitrogen atom (N) and four hydrogen atoms (H). Sulfate, the other component of this molecule, is made up of one sulfur atom (S) and four oxygen atoms (O). 


See the references for some common chemical formulas.


P.S.: You may also see superscripts in a chemical formula. These are like subscripts except that they are written toward the top of each element rather than the bottom. Superscripts indicate the charge of an ion and will have a + or - in front of them to indicate whether the charge is positive or negative, as well as a number to indicate the charge's magnitude. For example, consider `(NO_3)^-` . This is the symbol for nitrate, an ion (charged molecule) consisting of one nitrogen and three oxygens. The minus ("-") at the top of the formula indicates that this compound has a charge of -1. Superscripts can also use numbers to indicate higher or lower charges. ``


` `


` `

Comments

Post a Comment

Popular posts from this blog

Is there a word/phrase for "unperformant"?

As a software engineer, I need to sometimes describe a piece of code as something that lacks performance or was not written with performance in mind. Example: This kind of coding style leads to unmaintainable and unperformant code. Based on my Google searches, this isn't a real word. What is the correct way to describe this? EDIT My usage of "performance" here is in regard to speed and efficiency. For example, the better the performance of code the faster the application runs. My question and example target the negative definition, which is in reference to preventing inefficient coding practices. Answer This kind of coding style leads to unmaintainable and unperformant code. In my opinion, reads more easily as: This coding style leads to unmaintainable and poorly performing code. The key to well-written documentation and reports lies in ease of understanding. Adding poorly understood words such as performant decreases that ease. In addressing the use of such a poorly ...
Post a Comment
Read more

A man has a garden measuring 84 meters by 56 meters. He divides it into the minimum number of square plots. What is the length of the square plots?

We wish to divide this man's garden into the minimum number of square plots possible. A square has all four sides with the same length.Our garden is a rectangle, so the answer is clearly not 1 square plot. If we choose the wrong length for our squares, we may end up with missing holes or we may not be able to fit our squares inside the garden. So we have 84 meters in one direction and 56 meters in the other direction. When we start dividing the garden in square plots, we are "filling" those lengths in their respective directions. At each direction, there must be an integer number of squares (otherwise, we get holes or we leave the garden), so that all the square plots fill up the garden nicely. Thus, our job here is to find the greatest common divisor of 84 and 56. For this, we prime factor both of them: `56 = 2*2*2*7` `84 = 2*2*3*7` We can see that the prime factors and multiplicities in common are `2*2*7 = 28` . This is the desired length of the square plots. If you wi...
Post a Comment
Read more

What warning does Chuchundra issue to Rikki?

Chuchundra, the sniveling, fearful muskrat who creeps around walls because he is too terrified to go into the center of a room, meets Rikki in the middle of the night. He insults Rikki by begging him not to kill him. He then insults him by suggesting that Nag might mistake Chuchundra for Rikki. He says, "Those who kill snakes get killed by snakes."  He issues this warning to Rikki not to help keep Rikki safe but as a way of explaining why Rikki's presence gives him, Chuchundra, more reason to fear.  Chuchundra starts to tell Rikki what Chua the rat told him--but breaks it off when he realizes he might be overheard by Nag. He says, "Nag is everywhere, Rikki-Tikki." Rikki threatens to bite Chuchundra to get him to talk. Even then, Chuchundra won't overtly reveal any information. But he does say, "Can't you hear, Rikki-Tikki?" This is enough of a clue for the clever mongoose. He listens carefully and can just make out the "faintest scratch-s...
Post a Comment
Read more