Chemistry 1.1 - Atomic Structure (Subatomic Particles)

Chapter 1 : Atomic Structure

Section 1: Subatomic Particles

So, in this first chapter, we will be talking about the anatomy of an atom. Specifically in this first section, we are going to discuss about the subatomic particles. What's the importance of subatomic particles? Subatomic particles is what an atom is comprised of.

There are 3 subatomic particles (meaning, an atom is composed of 3 types of particles)

1. Protons
2. Neutrons
3. Electrons

Before we move onto talking about these 3 particles, one needs to understand what the atom itself looks like. There are 2 parts to an atom. 

1. Nucleus
2. Electron Clouds

Nucleus is the center of the atom. Surrounding the nucleus is the electron clouds. Below is a picture of it: 

Moving onto talking about the subatomic particles itself: 

Protons

• Protons reside in the nucleus of an atom.
• Protons charge is 1.6 x 10^-19 C. C stands for Coulombs. This is usually used in physics. In chemistry, this is equivalent to +1 Charge. 
• Protons mass is approximately equivalent to 1 amu. (Will discuss about amu in a couple sections from now). For now, just remember that amu stands for atomic mass unit. 
• The number of protons in an atom is unique for each element. (Click here to learn the difference between atom and an element)

Neutrons

• Neutrons are found in the nucleus of an atom as well
• Neutrons, like the name states, has a neutral charge. This means that, charge on a Neutron is 0. 
• Mass of a Neutron is slightly larger than that of protons but roughly speaking, it's about the same size
• The number of Neutrons varies not only between different elements, but also within ana element itself. When the number of Neutrons varies within an element, it's called Isotopes. I will mention about this again in a couple sections from now. 

Electrons

Electrons are going to be the most important particles in chemistry. Everything in chemistry and organic chemistry just revolves around the behavior of these electrons. So understanding how they work is crucial

• Unlike Protons and Neutrons, Electrons do not reside in the protons. They surround the nucleus and move in pathways in the electron clouds. More specifically, electrons move around nucleus in their orbitals, but we will talk about orbitals in the next chapter. 
• Each electron is associated with different levels and amount of energy
• Charge of an electron is equal to -1.6 x 10^-19 C. In chemistry, this is equivalent to -1 Charge. Notice, this is the exact opposite charge of a Proton. 
• Because protons have +1 Charge, and electrons have -1charge, the total charge of an atom is 0. This is called ground state. 
• However, sometimes, atoms can either gain or lose electrons. When this happens, we say the electron is excited. Note: Only electrons can be added or removed. Protons can neither be added to an atom or removed because they reside in the nucleus of an atom. Since electrons surround the nucleus, we can pluck an electron off or add an electron to the cloud/orbital in order to excite them. 
• In an element of ground state, # of protons = # of electrons. Take oxygen for example. Looking at the Periodic table, you can tell it has 8 protons. Because each proton = +1 charge, if an atom has 8 protons, it has +8 charge. Remember, for an atom to be in it's ground state, the total charge of an atom has to be 0. This means that, the net charge of electrons should be of -8. Since each electron has -1 charge value, there must be 8 electrons present. This holds true for any element. 
• Excited electrons: 
• When atoms are excited, meaning when they are not in their ground state, they are no longer referred to as atoms. They are now called ions. 
• When an atom gains an electron, the atoms becoming more negative because electrons possess negative charge So if oxygen were to gain an electron, it would have 8 protons and 9 electrons. The total charge of this ion would be +8 + (-9) = -1. A negative ion is called an Anion. (Mnemonic: It sounds like onion, which makes you cry while cutting, so it's bad --> Negative)
• When an atom loses an electron, the atoms has more protons than electrons. This means that, the atom is more positive now. So, if oxygen were to lose an electron, it would have 8 protons and only 7 electrons. The total charge of this ion would be +8 + (-7) = +1. A positive ion is called a Cation. (Mnemonic: Notice the t in cation looks like a + which refers to positive)
• Mass of an electron is about 1/1836 of a Proton. Since mass of an electron is extremely small in relevant to proton and a neutron, it's usually neglected when account for the total mass of an atom. Total mass of an atom = # of Protons + # of Neutrons. We will talk more about masses in a couple of sections from now. 
• Because subatomic particles are so small, the electrostatic force (forces that result from the opposite charges of proton and electron) of attraction between the unlike charges of a proton and electron outweighs the gravitational force of attraction. We will talk about gravitational forces in physics. For now, just remember that when we talk about atoms, we ignore gravitational forces. 
• Remember, I mentioned that electrons surround the nucleus? There are many electrons surrounding the nucleus depending the atom. Some are close to the nucleus, some are far the nucleus. Electrons close to the nucleus, have stronger attraction to the positively charged protons in the nucleus. So they are going to be more stable. Electrons far from the nucleus have less attraction to the positively charged nucleus (nucleus is positively charged because it contains protons and neutrons. Neutrons have a charge of 0. Protons have a charge of positive values. So the net charge is positive) and thus are not so stable. 
• What does more/less stable mean?
• Think of yourself on the ground, and on a cliff. If you are on the cliff, you have a lot of potential energy (you will learn about this in physics but you should have a general idea by now of as what potential energy is). Potential energy can be of many types. Some include, mechanical, chemical, electric etc. In this case, it's mechanical potential energy. When you hold onto this much of energy, you are not so stable. You are a risk of falling off the cliff and breaking you legs, nose and what not. So, More Energy = Less Stable. Likewise, if you are on the ground, you almost have zero potential energy. But you have very stable. You won't break as many things in your body if you were to fall over. So Less Energy = More Stable. 
• Similarly, when we talk about nucleus and electrons, think of nucleus as the ground and electrons an individual. When an electron is close the nucleus (when an individual is close the ground), there is less electrical potential energy and thus is more stable. Likewise, when an electron is far from the nucleus, (when an individual is far from the ground), it has lots of electric potential energy, and this is less stable. 
• Electrons, though are constantly moving, they can identified 90% of the time in certain places around the nucleus if we were to map it out and divide it into areas. Kind of like a real map, how it's divided into continents, countries, states, counties etc. Electrons can be divided into Shells, Sub shells and Orbitals. We will talk about electrons geography a lot in the next chapter. I am just mentioning this now because, I want you to understand what valence electrons are. Valence electrons are electrons that are in the outermost shell. Meaning, the shell that's far away from the nucleus. In more general terms for now, just know that certain electrons that are far away from the nucleus are called valence electrons. We will talk about which electrons particularly in the next chapter. 

Okay that's all about the subatomic particles. In the next section, we will talk about Atomic Weights.