In a previous post, we took a peek at the structure of the atom. We looked at how atoms (elements) build up in weight, most of which consists of positively charged protons and uncharged neutrons, roughly equal in mass to each other. The atomic number of each element is equal to its number of protons. In each of them are a number of electrons equal to protons; since you don’t get a shock when you, say, handle aluminum foil, the charges (plus and minus) obviously must be equal.
Electrons lie in regions of (probablistic) space outside of the core (nucleus) of atoms. These are known as orbitals (suggesting the model of the solar system I told you not to take too seriously). Just a reminder -these are tiny, really really tiny. When confronted with stuff or entities too small to visualize, scientists sort of construct models. Models are very useful, if you don’t take them literally. Often, as new information is discovered, models are modified, or discarded outright. Chemists pigeonhole electrons into orbitals designated “s”, “p”, “d” and “f”. I won’t bore you with what these things look like (remember, these are just models); suffice to say electrons are found in them.
Why don’t we look at Public Enemy #1, aka methane. The chemical formula for this bad boy greenhouse gas is CH4 , meaning that the moleculeconsists of a carbon atom chemically bonded to four hydrogen atoms. What happens is that carbon, with 4 valence electrons shares four electrons with hydrogen. Not an outright donation, as I described in my previous post, but a sharing. Relatively simple compounds often follow something called the Octet Rule – whereby they enter arrangements which provide 8 electrons, like the fat-dumb-and-happy “noble gases”.
The two basic types of chemical bond are ionic (where electrons are given/taken outright) and covalent, where they are shared. Ionic compounds, such as sodium chloride, aka table salt, when dissolved in water conduct electricity. This results from the water molecule being capable of separating electric charges (also known as ions). In the case of salt, the negative chloride ion (chlorine containing an extra valence electron) exists along with sodium ion (short a valence electron, charged positive) results in a solution which conducts electricity.
Most ionic bonding occurs with elements in Columns 1 and 2 forming compounds with those in Columns 16 and 17. More typically, we can look at a (seemingly) well understood compound, H2O. The formula tells us that each of two hydrogen atoms is bonded chemically with a single oxygen. Water doesn’t conduct electricity, in its pure form. No ions are present to do this. The bonding between the oxygen and hydrogens is covalent in nature.
The vast majority of chemical compounds exhibit covalent bonding. Even in large, complex molecules, the driving force forming compounds is to provide a pseudo noble gas configuration for each element. Exception is hydrogen, where a helium configuration (2 electrons) does the trick.
Carbon is found in the vast majority of compounds. It is part of just about every drug we take, along with most stuff we burn (combine with oxygen) to produce electricity or just stay warm. Unfortunately, most of the byproducts of burning are sent into the atmosphere. Many of them are greenhouse gases.
Next time, we’ll take a plunge into naming some of these chemicals (the stuff you probably hated in college or high school). We’ll try to make it stress-free (after all, no grades or any other such nonsense…..)
Rogernarc 