Hi, I'm Cathy with Level Up RN. In this video, I will be doing a review of important chemistry concepts that are important for understanding the structure and functions of microorganisms.
Specifically, I'll be talking about atoms, ions, chemical bonds, pH, and water. And at the end of the video, I'm going to give you guys a quiz to test your understanding of some of the key concepts I'll be covering, so definitely stay tuned for that. And if you have our Level Up RN Microbiology Flashcards, go ahead and pull out your flashcards so you can follow along with me.
Let's first review the components of an atom.
A proton is a positively charged particle located in the nucleus of the atom.
It has a mass of one atomic mass unit and a charge of plus one. The number of protons determines the identity of an element.
An electron is a negatively charged particle found traveling in the space around the nucleus of the atom in an energy shell.
An electron has a negligible mass and a charge of negative one.
The number of electrons in the outermost shell, which are the valence electrons, determines the chemical properties of the atom.
So if you have an atom with seven electrons in the outer shell, that atom is going to try and form bonds with other atoms in order to fill that shell. So that type of atom is going to be reactive.
On the other hand, if an atom has eight electrons in its outermost shell, which is the maximum number, it's going to be stable, and it's not going to form bonds with other atoms, so it's going to be unreactive.
And then a neutron is a neutrally charged particle found in the nucleus of the atom. It has a mass of one atomic mass unit, and it has a charge of zero.
Let's now touch on electronegativity. Electronegativity is the measure of an atom's ability to pull electrons towards itself, and understanding this concept will be helpful when we talk about ions, as well as polar versus nonpolar covalent bonds, which are topics we will be covering in this video.
On a periodic table, electronegativity decreases as we go down a group, and then it increases as we go across the periodic table from left to right.
So fluorine is going to be the most electronegative element in the periodic table.
Let's now talk about the difference between an uncharged atom and an ion.
So an uncharged atom will have no net charge because it has an equal number of protons and electrons.
An ion, on the other hand, will have a net charge, either positive or negative because it has an unequal number of protons versus electrons.
And there are two types of ions, which include cations and anions.
A cation is a positive ion that carries a positive charge. It forms when an atom loses an electron to a more electronegative atom.
So the number of electrons is going to be less than the number of protons.
Our Cool Chicken hint to help you remember cations is to think, "I positively love cats." So positively love cats. Cat ions are positive.
An anion is a negative ion that carries a negative charge. It forms when an atom gains an electron from a less electronegative atom. So the number of electrons is going to be more than the number of protons.
So if you're a Star Wars fan, you can remember that an anion is negative by remembering that Anakin Skywalker was pretty much a negative person with all the mass murder and such.
We're now going to discuss chemical bonds. The three main types of chemical bonds include covalent bonds, ionic bonds, and hydrogen bonds.
A covalent bond results from the sharing of electrons between two atoms. These are the strongest and most common bonds found in living organisms. With a nonpolar covalent bond, electrons are shared equally between the two atoms because there is no difference in the electronegativity between the atoms.
An example of a nonpolar covalent bond is the bond between a hydrogen atom and a carbon atom.
With a polar covalent bond, electrons are not shared equally. With this type of bond, electrons are pulled closer to the more electronegative atom.
So an example of a polar covalent bond is the bond between oxygen and hydrogen. Because oxygen is more electronegative, electrons are going to be pulled closer to the oxygen atom, giving it a slight negative charge, whereas the hydrogen atom is going to have a slight positive charge.
Next, we have an ionic bond, which results from the attraction between a cation, which is a positive ion, and an anion, which is a negative ion.
The most common and well-known example of an ionic bond is sodium chloride or salt.
Lastly, we have a hydrogen bond, which is a weak attractive force between a weakly positive hydrogen atom on one molecule and a weakly negative oxygen, nitrogen, or fluorine atom on another molecule.
So with a hydrogen bond, no electrons are lost, gained, or shared. The most common example of a hydrogen bond is the bond that forms between two water molecules.
Let's talk a bit more about water and some important terms related to water.
So a solvent is a substance that is capable of dissolving another substance, and water is an excellent solvent.
A solute is the substance that is being dissolved.
So when a solute, such as sugar, is placed in a solvent, such as water, the polar sugar molecules interact with the polar water molecules via hydrogen bonding.
We would describe a molecule such as sugar to be hydrophilic because it can form hydrogen bonds with water and be dissolved in water.
So hydro- means water and -philic means loving. So our Cool Chicken hint to help you remember what hydrophilic means is to think, "I'm in love with Phil."
On the other hand, we would describe a substance such as an oil or fat to be hydrophobic. So hydro- means water, and -phobic means fearing.
These substances are nonpolar, so they're not going to form hydrogen bonds with water, and therefore, they will not dissolve in water.
Lastly, we're going to talk about pH, which is the measure of the hydrogen ion concentration of a solution.
It is calculated as the negative logarithm of the hydrogen ion concentration, and this calculation results in a number somewhere between 0 and 14 on the pH scale.
So on that pH scale, when we move one unit, such as a pH of 2 to a pH of 3, this represents a tenfold change in the hydrogen ion concentration.
A neutral substance has a pH of 7, and this means that the amount of hydrogen ions in the solution is equal to the amount of hydroxide ions in the solution.
An acid has a pH of less than 7. This means that the substance donates hydrogen ions to the solution such that the amount of hydrogen ions exceeds the amount of hydroxide ions.
So examples of acids include stomach acid and lemon juice.
And then a base or alkaline substance has a pH that is greater than 7. This means that the substance removes hydrogen ions from the solution such that the amount of hydrogen ions is less than the amount of hydroxide ions.
Examples of alkaline substances include ammonia and bleach.
All right. It's quiz time, and I have five questions for you. You guys ready?
Number one.
A blank is a positive ion that forms when an atom loses an electron to a more electronegative atom.
The answer is...a cation.
Number two.
A blank bond is formed when electrons are shared equally between atoms.
The answer is...nonpolar covalent.
Number three.
A blank bond is a weak attractive force between a hydrogen atom on one molecule and an oxygen atom on another molecule.
The answer is...hydrogen.
Number four.
A water-loving molecule that can be dissolved in water is described as blank.
The answer is...hydrophilic.
Number five.
A substance that donates hydrogen ions into a solution, resulting in a pH less than 7 is considered a blank.
The answer is...an acid.
All right. That is it for this video. I hope you found it to be helpful. Take care and good luck with studying.
[BLOOPERS]
Lastly, we have a hydrogen bond, which is-- and an oxygen atom on a--
