Tag: Quantum

Emission and absorption spectrum

Emission and absorption spectrum

Emission and absorption spectrum

11/22/16

“Why do elements absorb light?”

 

Light is something that we literally see everyday, whether it be from the sun shining down on civilization during the day, the incandescent light bulbs lighting up our night, or the flashlights we use to read in bed. However, as light is both a wave and a particle, it has to interact with material objects when it makes contact, so what happens when it does so? Well, let’s think about it. We know that light is composed of atomic-size forms of matter known as photons, and we also know that as a result of the wave-particle dualistic nature of light, these photons will have a wavelength associated with them. And since light is emitted by radiation, these photons will have a distributions of multiple wavelengths, all of which have a corresponding energy. Furthermore, all material objects are comprised of atoms, which have discrete energy levels. So when a photon wave hits a material object, the atom can only absorb the photon if it corresponds to the precise energy level. This energy level will stay elevated for a limited amount of time, and will soon fall back down to the original energy level, emitting  a wave of the same energy level. If one were to take an empirical measurement of the wavelengths being emitted by constructing an emission and absorption spectrum, then one would be able to identify the element present! 

London dispersion

London dispersion

London dispersion

11/11/16

“What is the weakest of the intermolecular forces and how does it form?”

 

As a result of the nature of quantum mechanics, we know that in atomic structure, electrons do not orbit around the nucleus in a newtonian fashion, but instead are located in probability densities surrounding the core. Since electrons will move around in such a manner, the charge distribution of an atom is bound to become slightly asymmetric with time. Consequently, these asymmetric atoms will interact with other asymmetric atoms to form very subtle electric dipoles, resulting in a very weak intermolecular force. Scientists and Engineers have termed this phenomena to be London dispersion, and it is found to be the weakest of all the intermolecular forces. Despite this, as a result of it’s universal nature, all molecules are found to exhibit london dispersion
  

Spin quantum number

Spin quantum number

Spin quantum number

10/05/16

“How can we describe the angular momentum of an electron?”

 

The orbits of electrons around the central nucleus of an atom is a very complex matter. And because of this, we will have think to think of creative ways to describe the myriad of elements that make it up. So to make things simpler break this problem down into smaller components, such as the angular momentum. When an electron transits around the central nucleus, it has both an angular momentum from the orbit and another one resulting from the spin around it’s own axis. The combination of these two elements will result in a vector quantity called the spin quantum number. The spin quantum number represents the magnitude (½) and the direction 9+ or -) hat the angular momentum of the current electron. When electrons enter into subshells, they enter each orbital that is currently unoccupied. If the elements only has unpaired electrons, then this spin quantum number will be considered positive, and if the electrons begin to pair up, then the spin quantum number will be considered negative.

Quantized energy

Quantized energy

Quantized energy

10/04/16

“How does energy work on the quantum scale?”
Energy is a most bewildering phenomena. It is the very thing that literally drives the physical universe, yet we have no complete understanding of it. I fact, our understanding of energy breaks down even further when we go into the quantum world. On this scale, energy is not a continuous but a discrete phenomena! This means that energy comes in chunks instead of being “On a scale”. Let me elaborate using a metaphor. on the human scope, energy is measured like the volume of a liquid, it’s size can occupy a whole range of values, going into myriads of different decimals places, while on the quantum magnitude, energy is measured like drops of the liquid, being indivisible (for example, you can’t have half a drop of water). Energy in the quantum world through waves of light in units called quanta, Which are equal to a measurement called Planck’s constant (numerically equivalent to 6.63*10^-34 joules seconds) times the wavelength of the light. This relationship can be symbolically represented as E=h*lambda, with E being energy h being Plank’s constant, and lambda being the wavelength of light.

Atomic clocks

Atomic clocks

Atomic clocks

07/10/16

“Is it possible to have clocks accurate to a billionth of a second?”

We use clocks to keep time everyday. Whether it be for scheduling flights or processing the internet, civilization depends on clock technology to keep everything in balance. Clocks work by measuring the oscillations of a pattern, such as measuring how long a pendulum takes to swing back and forth or the earth to move around the sun. However, such machines are not always perfect. Since clocks (of all types) are physical objects, they are subject to the physical laws of the universe. Consequentially, these contraptions are prone to perturbation, which in effect makes them liable to becoming out of sync with other clocks. These inconsistencies add up over time (pun defiantly intended), and if they go on for too long, then drastic consequences can happen. For example, high speed finance trading could go asunder, which would have devastating effects on the global economy.

So how can we make a clock so accurate that we would never have to worry about civilization collapsing?

Well, luckily for people anxious about such an event, scientists and engineers have constructed marvelous devices known as atomic clocks. Atomic clocks work by measuring the internal oscillation of a cesium atom. Cesium atoms vibrate over 9 billion times in one second, and atomic clocks base their own measurements off such vibrations. Atomic clocks that are so accurate that commercial units are accurate to one second in 3 million years! Because of this genius design, scientists and engineers now base the unit of the second is based upon how  atomic clocks can measure the osculation of a cesium atom.

Ionic bonding

Ionic bonding

Ionic bonding

07/05/16

“What happens when ions of opposite and equal charge react?”

Let’s think about something. We know that ions are atoms with a net electric charge. We also know that when a positive and a negative charge are close to each other, there will be an electric force that pulls them together. So what happens when ions with charges of equal magnitude and opposite sign come within the vicinity each other? Well, if we use our own scientific intuition, then we would know that there will be an attractive force between the objects, causing them to be pulled together. These atoms will form a bond which chemists have decided to term an ionic bond. Ionic bonds are between metals and non-metals, are very hard to break (often melting only at high temperatures), and can be conductive when they are in liquid form.

Covalent bonding

Covalent bonding

Covalent bonding

07/04/16

“What happens when atoms share electrons?”

Atoms often have free space for electrons in their valence shell, which makes them unstable and prone to reaction. However, is it possible for atoms to share their electrons in order to fill the void? Let’s look at an example. Oxygen has only six of its eight valence electrons occupied, while hydrogen has one out of two. This means that oxygen needs to find a way to retrieve two electrons and the hydrogen needs to find a way to receive one electron. This can be accomplished if two hydrogen atoms shared their electrons with the oxygen atom. Then the oxygen would have it’s valence shell filled and the hydrogen would also. This will for a chemical bond known as a covalent bond. Covalent bonds are completely made up of non-metals, and they are extremely strong and durable, making it very difficult to dissolve a covalent bond.

Numerical electron configuration

Numerical electron configuration

Numerical electron configuration

07/03/16

“How can we quantify electron configuration?”

When dealing with electron configuration, wouldn’t be usefull if we could somehow create a framework to conceptualize everything? As discussed earlier, the electrons of an atom are organized into shells and orbitals, the former dealing with the distance from the center of the nucleus, and the latter dealing within the probabilistic location To start off, we will assign a number to each of the atomic shells, with the first shell being called the “first shell”, the second the “second shell”, and so on. Furthermore, each of these shells will be divided into subshells. Subshells are the set of atomic orbitals that are most similar to each other. The first shell will have one subshell (called the 1s subshell), the second shell will have two (the 2s and 2p respectively), the third will have three (3s, 3p, and 3d), and so on. Each of the letters indicate a different orbital of the subshell. Each orbital can hold two electrons, and each subshell will be able to hold 4L+2 electrons, with L being the orbital value of the subshell (for example, the s subshell will have an orbital value of 0,the p a 1, and so on).

Now, how do we incorporate the change in electrons into this system? When electrons flow into an atom, they will enter the orbital with the lowest level of energy associated with it, as that is the easiest one to deal with. The two factors that affect the energy level are the shell and orbital value. As a result, it is possible to have an shell with a higher value but a lower orbital be filled before  one with a lower value shell but higher orbital. For example, the 4s orbital will be filled before the 3d one since the 3d has a higher energy level. The pattern for this phenomena can be seen on the picture for this article.

Finally,  this brings us to the outermost shell of the atom. If this shell, termed the valence shell by chemists, has a lack of filled space, then it will be able to react with other chemicals to create chemical reactions and make chemical bonds.

Intro to electron configuration

Intro to electron configuration

Intro to electron configuration

07/02/16

“How can we find out how much free space an atoms has for electrons?”

All atoms have the potential to have electrons. However, how can we find out how many electrons an atoms has and how much it can hold? To solve this question, let’s start off with one fact. All electrons revolve around the nucleus. Because there is a mutual interaction between the two particles, there will be a certain level of energy associated with the two particles that binds them together. Furthermore, as a consequence of the laws of quantum mechanics, all energy levels are in discrete forms.  When the electron receives enough energy to surpass the binding energy, they will jump to the next possible level. The energy required to surpass the binding force is called the ionization energy and the different levels are called valence shells. As a result of the Heisenberg uncertainty principle, these electrons will have different possibilities of location within these valence shells, and that probability depends on the amount of electrons inside. These probabilistic locations are called orbitals. Chemists have termed these series of classifications to be the electron configuration of the system.