I typed this up because I was bored, and I guess I wanted to review some stuff from college. Come to think of it, the only information actually relevant to this discussion is in the last secion, so feel free to skip ahead to that. Just so you know, I didn’t pull this stuff out of my head; I had to consult some old textbooks for this information (specifically, Chemistry: Matter and Its Changes by Brady, Russell, and Holum). I cannot guarantee 100% accuracy of the following, so if you know I’m wrong on something, please point it out. I’d appreciate the opportunity to learn. So without further a due, here we go.
Darkdog’s Excessively Comprehensive Guide to Sodium
Quantum Mechanics
To begin, I’m going to give you a crash course in quantum physics. There are several facets to quantum physics that all fit together.
Planck’s Law- There are discrete (i.e. quantized) levels of energy. Hence, the term quantum mechanics.
The Heisenberg Uncertainty Principle- You can never know with perfect certainty where a particle, such as an electron exists. You can only know the probability of that particle existing in a given area in a given time frame. Observing something changes the very nature of that thing. So for all you peeping toms out there trying to stare through an electron’s window at night, keep in mind it knows you’re watching.
The Photoelectric Effect- The energy from a photon (electromagnetic wave) is directly proportional to its wavelength.
The Schrödinger Equation- All matter is a wave. The Schrödinger equation looks very similar to the equation for an electromagnetic wave, an acoustic wave, or an ocean wave. The main difference is the thing that’s actually waving. In an ocean wave, it’s the water that’s waving. In an acoustic wave, it’s the air molecules that are waving. In an electromagnetic wave, it’s the electric and magnetic fields that are waving. So what’s waving in the Schrödinger equation? The probability of a particle’s existence. Huh? Yeah, pretty abstract and weird. For the sake of this discussion, don’t bother trying to understand it beyond that. I really don’t.
Wave-particle duality- Particles can act as waves. Likewise, electromagnetic waves have momentum, which is a concept associated only with matter in classical physics. So matter acts like waves and waves act like matter.
The Structure of Elements
All atoms consist of neutrons, electrons, and protons. The nucleus of an atom consists of the neutrons and protons. Outside of that, electrons are spinning around. The type of element is determined by how many protons are in the nucleus. There are the same number of neutrons and in general, the same number of electrons. The protons and neutrons are tightly held in the middle of the atom by very strong nuclear forces. The electrons are held in the atom by much weaker electromagnetic forces. Protons have a positive charge and electrons have a negative charge. Remember that opposite charges attract whereas same charges repel. Both protons and electrons hold a charge of 1.602E-19 Coulombs, which is referred to as the “elementary charge” and represented as a constant by e or sometimes q. When an atom has the same numbers of electrons and protons, their charges cancel each other and the net charge is 0.
The way electrons are structured around an atom is determined by the rules of quantum mechanics (glad we went over that now, aren't you?). When I refer to the energy of an electron, I refer to its potential energy. It’s much like gravity. There’s a force on electrons that attract them toward the nucleus. That force is much like the gravitational force attracting you and me to the earth. If you stood at the top of a cliff, you would have a much greater potential energy than if you were standing at the bottom of the cliff. It’s the same with electrons. The further away they are from the nucleus, the greater potential energy they have.
Each electrons in an atom occupies its own “state”. These states are divided into four categories. From biggest to smallest, they are shells, subshells, magnetic quantum number, and spin quantum number. This works much like your address. You have a country (shell), then state or province (subshell), then a city (magnetic quantum number), then a street address (spin quantum number). Just because a state exists doesn’t mean it has to be occupied by an electron. Not every address within your city is occupied. Some entire cities may be empty (ghost towns). In fact, entire states can be empty (i.e. Wyoming. Well, close enough)
Around the atoms, there are “shells”. The shells are referred to as n (called the principle quantum number) and are labeled from one up. The first shell (n=1) is the lowest energy shell. As n increases, so does the energy of the electrons. Think of shells as circles around the nucleus that contain electrons (like rings in a tree). The first shell is the closest circle and the higher shells are further away.
Within each shell, there are “subshells”. The subshells are referred to as l (lowercase L, called the secondary quantum number) and are labeled from zero up. Each subshell also has its own letter, which seems somewhat arbitrary. For l=0, the letter is s. For l=1, the letter is p. For l=2, the letter is d. For l=3, the letter is f. Beyond that, it goes in alphabetical order starting with g. I don’t know who came up with that lettering scheme, or what they were drinking when they did. The s,p,d, and f subshells are the ones you’ll hear about most.
Subshells are then divided by the magnetic quantum number, or m sub l (l is really a subscript, but I can't do that in the forum, so I have to say m sub l). m sub l is a integer that ranges from –l to +l.
The final division is the spin quantum number, or m sub s. This can be either +1/2 or -1/2. This is often referred to as up or down.
So, how many electrons can fit into each of these categories? Let’s start from the top with the spin quantum number. One electron can occupy the up spin and one electron can occupy the down spin.
Each magnetic quantum number can have two spin quantum numbers (up and down).
The number of magnetic quantum numbers inside a subshell is determined by which subshell it is. Since m sub s can go from –l to +l, that means there are 2l+1 magnetic quantum numbers inside a subshell. For example, if l=3, then m sub s can be -3,-2,-1,0,+1,+2,+3. In this case, 2l+1=7. You can count that there are seven numbers there.
The number of subshells in a shell is equal to n. That’s easy. So for the n=3 shell, there are three subshells.
There can be infinity shells, but in reality, you only see as many as about 7.
It’s important to know how many states are in each subshell. Using the information above, we find it to be the following:
l=0 (s subshell): 2 electrons
l=1 (p subshell): 6 electrons
l=2 (d subshell): 10 electrons
l=3 (f subshell): 14 electrons
Also, using the above information, we’re going to figure out which subshells are in which shells.
n=1: s
n=2: s,p
n=3: s,p,d
n=4: s,p,d,f
This is important for notating the electrons in an atom. Let’s represent the electrons in an arsenic (As) atom. Arsenic has 33 electrons (assuming none have been ripped off or added, which is possible, as we’ll get to later). Here’s how that representation would look.
As 1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 4s(2) 3d(10) 4p(3)
The big numbers are the shell. The letters (s,p,d) are the subshells. The numbers in parentheses should be superscripted, but again, I can't do that here, so I put them in parentheses. They are the number of electrons in that subshell. The order goes from lowest energy level to highest energy level. The 4s subshell comes before the 3d subshell because the 4s subshell actually has a lower energy than the 3d subshell (the explaination as to why that is exceeds the scope of this guide). There is a way to represent the magnetic quantum numbers and spin quantum numbers, but for our needs, that won’t be necessary.
If you add the superscripted numbers, you get 33 electrons (2+2+6+2+6+2+10+3=33). All of the subshells are full except for the last one, 4p. The 4p subshell can hold 10 electrons, but it only holds three, because that's all that's left after the lower subshells take up the first 30. Valence electrons are the electrons in the outermost shell. In this case, the outermost shell is 4. Arsenic has 5 valence electrons. Since valence electrons are the ones responsible for most of the chemical behavior of that element, we can ignore the electrons in lower shells and represent just the valence electrons as such:
As 4s(2) 4p(3)
If you look at the periodic table, it’s actually divided by subshells. The two columns on the far left contain the elements whose highest subshell is s. The six columns on the far right contain the elements whose highest subshell is p. The ten columns in the middle represent the elements whose highest subshell is d. The two rows at the bottom with 14 columns represent the elements whose highest subshell is f (Technically, they should be between the s columns and d columns, but then the table would be too wide, so they put them at the bottom. It’s kind of like how they show Hawaii and Alaska in a corner of the US map so the map isn’t too big). 2,6,10,14- those numbers should sound familiar (they're the number of electrons in subshells). The only exception to the above is Helium. It’s highest subshell is 1s, but it’s on the far right. The reason because it’s an inert gas, and all the inert gases are placed over there. Row one contains 1s, row two contains 2s and 2p, row three contains 3s and 3p, row four contains 4s, 3d, and 4p, and so on.
Sodium and Salt
When sodium combines with chlorine, it forms sodium chloride, also known as salt. There are many different types of salt, but when we refer to salt in regards to food and nutrition, we mean sodium chloride.
Take a look at your periodic table and find sodium (symbol Na). It’s number 11, meaning it has 11 protons, 11 neutrons, and 11 electrons (normally). It’s in the third row, first column. Its highest subshell is 3s and that subshell has one electron. It has one valence electron which is represented as such:
Na 3s(1)
It can also be represent by a Lewis symbol, where each dot represents a valence electron:
Na .
Now find chlorine (symbol Cl). It’s number 17 on the periodic table. It has 17 protons, 17 neutrons, and 17 electrons (again, under normal conditions). It’s in the third row, second column from the right. Its highest subshell is 3p and that subshell has five electrons. It has seven valence electrons (2 from 3s and 5 from 3p). Here is its representation.
Cl 3s(2) 3p(5)
or
..
.Cl:
..
Chlorine’s valence shell (n=4) has room for one more electron. When sodium and chlorine combine, the one valence electron from sodium occupies that free space in chlorine and they both share two electrons. The Lewis diagram for Sodium Chloride looks like this.
..
Na:Cl:
..
However, if sodium chloride every break up (by being dissolved in water for instance), the chlorine atom keeps that extra electron (“That bastard! He came into my life, bonded with me, took my only valence electron, and left! I bet he’s bonding with that floozy, Potassium, right now!” Poor sodium
). So anyway, sodium will be left with one missing electron and chlorine will have one extra electron. Since sodium has 11 protons and now only 10 electrons, it’s net charge is no longer zero; it’s positive. The net charge is now +e. It’s referred to as a positive ion, or cation. Chlorine, on the other hand, now has a negative charge. It has 17 protons and 18 electrons, so the net charge is –e. It’s called a negative ion, or anion. Now that they have net charges, they can conduct electricity and respond to electric fields.
Sodium in Milk and the Body
The body’s nervous system uses ions in electrolytes to transmit messages across nerves and to muscles. Sodium is one of the primary ions it uses. Sodium isn’t bad for your health. In fact, you tend to die without it. On the other hand, in excess, it can be harmful. As a toxicologist would say, the quantity makes the poison. There’s an optimal level of sodium intake and there are negative ramifications to consuming more or less than that. The reason sodium has a bad reputation is because people tend to get too much of it, so it’s usually beneficial to limit intake and get closer to the optimal amount. It’s also possible to consume too much fiber, but people tend to not get enough of it. That’s why you see magazine articles about increasing your diet intake. If people did get too much fiber, you’d see magazine articles about how to decrease your fiber intake.
A cow’s nervous system needs sodium as much as a human’s. The cow does not need to be fed pure salt. Fortunately, salt appears in many foods, so just from eating grass or whatever, the cow will get enough sodium. As for the calf, its only food source is its mother’s milk, and the calf needs sodium as well. If cow’s milk lacked sodium, the calf would die or at least become very sick. Hence, sodium comes naturally in milk.
Thanks for reading! In next week’s excessively comprehensive guide, I will cover the topic of string theory in its entirety including the parts the physicists haven’t figured out yet! Until then, ciao!
I already stated many times that soduim and salt are not the same thing.
