Chapter 2 Post

I. Summary:

Everything that is currently living or has ever lived is composed of matter. Matter is defined anything that contains mass and occupies space. All matter is composed of atoms. Atoms are the teeny tiniest units of atoms that form all chemical substances.

Each specific atom type is called an element. An element is a pure substance of only one kind of atom. Three subatomic particles make up atoms. They are protons, neutrons and electrons. Protons have a positive charge and are found in the nucleus. Neutrons have a neutral (no) charge and are also found in the nucleus. Electrons have a negative charge and are found in orbitals, which I discuss below.

Electrons are extremely fast, so it's hard to predict the location of a given electron. But we can describe where there is a high probability of finding one, using regions called orbitals. You can think of it as a cloud. Spherical orbitals are called s orbitals. P orbitals have a propeller or dumbell shape. Slightly confused? I was at first too. But looking through the pictures in the book helps.

Orbitals occupy energy shells, aka energy levels. The inner energy shell can hold only 2 electrons within an s orbital. The second shell has 1 s orbital and 3 p orbitals. Each of these orbitals holds a pair of electrons, so the second shell holds 8 total. Electrons tend to fill the s orbitals first, and then the p orbitals one electron at a time.

The majority of atoms have outer shells that aren't completely filled with electrons. Those electrons in the outer shell are called valence electrons. Valence electrons are a crucial part of bonding, which is coming up soon.

Each element has a unique atomic number.
Atomic number = Number of protons = Number of electrons

Now let's talk about atomic mass. It's measured in daltons, aka atomic mass units. One dalton = 1/12 the mass of a carbon atom, so carbon has a mass of 12 daltons. Then there are moles. A mole of any substance has the same number of particles as there are atoms in carbon. To put it simply, a mole of all substances have the same number of atoms. This number, 6.022 x 10^23, is Avogadro's number.

An element can have different numbers of neutrons, called isotopes. Isotopes don't change the charge of the atom, but they change the mass. There are also unstable isotopes called radioisotopes.

The next major part of the chapter talks about bonds. There are 3 major types; covalent (which can be further subdivided into polar and nonpolar), hydrogen and ionic. Each type of bond has specific characteristics that I found quite simple.

Then there's free radicals. A free radical is a molecule that has an atom with a single, unpaired electron in its outer shell. Free radicals are very lonely so they try to steal electrons from another molecule's atom. This pretty much sets off a chain reaction of free (lonely) radicals.

Let's move on to chemical reactions (fun!). These happen when substances change into other substances. They require an energy source and reactions in living organisms may need a catalyst (like enzymes).

Next the book talks all about water. A solution is composed of a solvent and a solute. In aqueous solutions water is the solvent. Hydrophillic means water loving and hydrophobic means water fearing. There's also amphipathic molecules that have both polar and non polar regions. Solute concentration is how much solute there is in a solution. It's usually in g/L. Molarity is the number of moles of a solute dissolved in a liter of water.

II. Useful Materials

I found this video pretty helpful with mole conversions, something described in the chapter. The man in the video works it out very simply, step by step.

So, I know what you're thinking. This guy is slightly crazy. But, he does explain and prove the point well about how hydrophillic and hydrophobic bonds work.

This article from PubMed talks about interaction energies between different ions. Different model complexes are tested with different ions. Also mentioned is interaction energies underlying the theoretically predicted metal-ion selectivity and the effect of geometry optimization on these values. This relates to our chapter because it highlight intricate ionic bonds and how they interact with free energies.