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Notes 2 Archive |
Gaffer Variety:
Elements 1 SN2 003:
By Willie Gaffer:
Before I go on with the discussion of the periodic table, I
must report on an error I made. I don’t want to
misleads anyone. In essay “G25, Our
Dilemma” I indicated my intention to purchase a chemistry set. My
rational was that it would help me to learn chemistry. I was wrong and, of
course, it’s my own fault. I was not thinking
well when I did that. However, I ordered the Chem. C2000 kit marketed by
My own opinion after perusing the manual is it should not have been hawked as a chemistry kit. It should have been called a magic kit. That is how the manual approaches chemistry. It presents a series of loosely related experiments which were obviously selected for their “Wow, Gee Whiz” appeal to kids. Although the experiments were sort-of explained in terms of the chemical processes involved, there was little attempt made to link them back to the basic principles of chemistry. In fact, the manual was replete with the terms and phrases of a magic act. Here are a few:
Wonderland of chemistry.
Amazing, mysterious, and a little like magic.
Astound your friends and family and put on shows, just like a magician.
The chemist as a magician.
And so on.
Perhaps, a bit later, if I need to do some experiments to pin down an elusive theory, I will have some of the necessary equipment in this kit. While searching for this kit, I also found it is possible to purchase other chemistry equipment. There are companies that specialize in supplying that stuff. The internet is great for that. We need not go from store to store to find out what we need is not available locally. We can find the big suppliers online. As to the kit, it’s not a total loss. I’ll keep it until my granddaughter is a bit older. Perhaps she will want to do some magic tricks with Gramps. I will simply make sure I relate the stuff back to basic principles when we do the tricks.
For now, I don’t see how it can be possible to say anything useful about chemistry, without an understanding of the basic structure of the individual elements. That is where the chemistry kit failed and where the periodic table of the elements comes in, but that is just the beginning. Let us borrow two of the definitions of element from Microsoft’s Bookshelf to begin.
element (èl´e-ment) noun
1, a fundamental, essential, or irreducible constituent of a composite entity.
4, Chemistry & Physics. A substance composed of atoms having an identical number of protons in each nucleus. Elements cannot be reduced to simpler substances by normal chemical means.
As a place to begin, that is adequate. Chemistry is about elements and compounds and the processes we deal with in chemistry are about the interactions between elements and compounds. We want to understand how they combine and mix, or refuse to combine and mix, and how the combined elements can be separated. The basis for this understanding lies in the very structure of the individual atom of the element. Just so we don’t get tangled in our underwear about words, element and atom mean essentially the same thing. An atom of an element is an indivisible, by chemical means, unit. We are dealing with chemistry for now. In physics, an atom is definitely divisible, as in atomic bomb.
For our purposes, an atom is composed of protons, neutrons and electrons. Since no one has ever seen a proton, neutron, or electron, we must accept that as a useful theory. However, all of my discussions will assume it is true. Further, the nature of the atom will depend on its structure and will determine what kind of atom it is, be it hydrogen, oxygen, or something else. There is a very definite difference between a hydrogen atom and an oxygen atom. This is determine by the number of protons in the atom.
An electron is a subatomic particle with a negative charge and a mass of 9.1066 × 10-28 gram. That’s pretty tiny. The proton is a subatomic particle with a positive charge and a mass 1,836 times the mass of an electron. That’s still pretty tiny. A neutron is a subatomic particle that is electrically neutral and has a mass 1,839 times that of the electron.
An atom consists of a tightly packed center or nucleus of protons and possibly neutrons, surrounded by a cloud of electrons. The electrons in the cloud are normally equal to the number of protons in the nucleus. The proton carries a single positive electrical charge and the electron carries a single negative electrical charge. This means the total positive charge of the protons is normally exactly offset by the total negative charge of the electrons. This makes the atom electrically neutral.
We have three values of interest associated with the elements. These are the atomic mass, atomic weight, and the atomic number. The atomic mass is the mass of one atom of the element. For example, hydrogen has an atomic mass of 1.00794 while oxygen has an atomic mass of 15.9994. The unit used to express the atomic mass is the atomic mass unit (amu). This unit is defined as 1/12 of the mass of a carbon-12 atom. I will be dealing with carbon later since it is the main component of all organic compounds and one of the ingredients in carbon dioxide, CO2, the other being oxygen. That is one of the things we will want to eliminate from automobile exhaust.
The atomic weight is just the weighted average of the masses of all the naturally occurring isotopes of the element. We will do more on isotopes later. For now, an isotope of an element is one having extra mass due to the presence of extra neutrons in the nucleus. The atomic number of an element is just the count of the protons in the particular atom. The periodic table of the elements is arranged in order of the atomic numbers of the elements. For example, hydrogen, first on the table, has an atomic number or 1.
The electrons are the important part of the atom in chemistry. They are involved in how our elements can combine into compounds. A compound is a complex chemical structure that is formed when two or more different elements combine. The compound will have chemical properties that are unique to the particular compound and different from the properties of its component parts.
That brings us to the difference between a compound and a mixture. Air, for example, is a mixture of nitrogen and oxygen, but the two elements retain their distinct chemical properties. Water (H2O) is a compound and has properties that are very different from the properties of it’s constituents, hydrogen and oxygen.
This is just a beginning, but it is a lot to absorb in one reading. It is very important to have a firm grasp of these basic principles of chemistry lest we get lost in the details later on. Let us leave it there and carry on with a discussion of electrons in the next notes.