Fundamentals of chemistry
The Fundamentals of Chemistry is an introduction to the Periodic Table, stoichiometry, chemical states, chemical equilibria, acid & base, oxidation & reduction reactions, chemical kinetics, inogranic nomenclature and chemical bonding.
Periodic Table of Elements
Each chemical element in the universe has unique properties which distinguish it from all of the other chemical elements. Though each is unique, the elements can still be grouped by their commonalities in a useful and meaningful way. The periodic table groups the elements by properties. For the History of the Periodic Table, check out Wikipedia's History of the Periodic Table.
The Periodic Table is available here: Periodic Table on Wikimedia Commons and explanations will be based on this table. A good idea is to have a printed hard copy of the periodic table for ease of access and reference.
Each element has its own box and these boxes make up groups and rows. There are eighteen groups (or families or columns) on the periodic table. Each one represents how many electrons are attached to the elements and correlate to how many valence electrons are present. Electrons are negatively charged subatomic particles that revolve around the nucleus of the element. Valence electrons are electrons that are on the very outside of the atom. There are seven periods (or horizontal rows) that describe electron shells, but more details on electron shells will be discussed in advanced pages.
Traditionally the boxes have certain informative parts about the element. Let's look at hydrogen's box. The "1" in the top corner is the atomic number, which deals with how many protons, or positive charges, are in the atom. The "H" is the symbol for Hydrogen. All the elements get a one or two letter symbol (there are a couple of exceptions with undeclared elements). The number at the bottom is the atomic weight or atomic mass. 1.00794 represents how many grams are in each mole (6.022×1023 entities) of hydrogen. The atomic mass is a very important part of chemistry and has many applications throughout.
There are eight distinct groups that need to be discussed. The first two groups (1A and 2A) as well as the six on the very right (3A-8A). These are called representative elements. Group 1A are alkali metals (except Hydrogen which is a non-metal) and Group 2A are alkaline earth metals. Group 3A through 8A are mixed in properties, but there are specific trends.
Chemical compounds are groups of two or more elements that are held together by chemical bonds. The bonding often leads to the rise of new properties besides those of its constituent elements. For example, the compound Sodium Chloride (NaCl), is composed of one ion of Chlorine bonded to one ion of Sodium. Sodium, in its natural form, is a solid metal element which is highly reactive and produces a lot of effervescence when reacted with water. Chlorine, in its natural form, is a non-metal element which is composed of many diatomic molecules of Cl2, and exists as a pale green gas that is toxic if inhaled in large amounts. The compound Sodium Chloride, however, is none other than the simple table salt applied to foods. The reason for the rise of these new properties lies in the type of bonding and the elements that make up the compound. This will be discussed in more detail in later sections.
Chemical Equations are a way of expressing a chemical reaction. They present chemical species with the chemical symbols of the elements that compose them and subscripts which present the actual number of particles of that element, whether they be atoms or ions, which make up the compound. For example, consider the reaction shown below:
2H2(g) + O2(g) ===> 2H2O(l)
On the left side of the arrow, you can see two compounds represented. These are the reactants - the chemical species which rearrange to give the product, which is the chemical species represented on the right side of the arrow. The first reactant, H2, represents a Hydrogen molecule. The subscript '2' shows that there are two atoms of Hydrogen that chemically combine to produce the molecule. Therefore, every molecule of H2 contains two Hydrogen atoms chemically-bonded to each other. The same concept applies to the reacting molecule of O2 to the right of it. You will also notice that there appears to be another subscript next to the numbers, like (g) and (l). These are called state symbols, and they represent what physical state the chemical species exist in while the reaction is underway. The subscript (g) means that the chemical species O2 and H2 both exist as gases before they react, and the subscript (l) means that the chemical species H2O exists as a liquid when it is formed by the reaction. Another thing to note is that there appear to be numbers written to the left of some chemical species in the reaction, namely the H2O and the H2. Their use is a representation of the simplest whole number ratio of the amounts each substance in the reaction mixture. For example, the above equation shows that every molecule of O2 reacts with two molecules of H2 to form two molecules of H2O. The reason these are important to the reaction is discussed further in the 'Balancing Chemical Equations' section of the Stoichiometry segment below.
Stoichiometry is used to analyze quantitative measurements with relation to reactants and products of a chemical equation. The chemical equation is a symbolic representation of a chemical reaction. The reactants of a chemical equation are justified to the left which gives reference to its definition, the substance used or consumed in a chemical reaction. The products of a chemical equation are justified to the right, and is defined as the substance that is yielded or produced in a chemical reaction. In order to completely understand stoichiometric relationships, one must consider the law of conservation of mass, the law of definite proportions, and the law of multiple proportions. Remember that mass or matter is neither created nor destroyed.
Among the properties of elements are states. There are 3 fundamental states of an element: solid, liquid, and a gas. They are indicated by subscript with (s), (l), and (g) respectively and assigned with the appropriate compound or element in the chemical equation. Plasma can also exist, which is an ionized gas with special properties.
Stoichiometry allows chemists to quantitatively analyze relative relationships between substances in a chemical equation.
Balancing chemical equations
Ethyne is added to oxygen gas to yield carbon dioxide and water. This reaction could be written as follows:
- Unbalanced equation
However, the above equation is not balanced.
- On the left side there are two Carbon atoms (C), two Hydrogen atoms (H) and two Oxygen atoms in total.
- On the right there is one Carbon atom, three Oxygen atoms, and two Hydrogen atoms.
Note that in order to properly count up the atoms in an equation, it must be noted to count up atoms with respect to the coefficient and subscripts. Careful notice should be made to compounds and polyatomic ions, since these are grouped together in relation.
In order to balance the equation correctly, a number, known as a coefficient must be added to the front of each representation in a chemical equation.
- Correctly balanced equation
As can be seen, the subscripts were not touched, only whole numbers were added to the front of all the formulas, as needed. The coefficients may be fractions, which are generally used in thermochemistry but for all intents and purposes, whole numbers are generally used.
It would not be correct to balance it by changing the subscript numbers.
- Incorrectly balanced equation
By changing the subscripts you are changing the chemicals involved in the reaction. In the above, is ozone, not normal oxygen, and is not a stable compound. A small change in the subscripts and makeup of an individual compound yields a whole different set of properties.
There are five states of matter, plasma being the most common in the known universe. The other three common states are gas, liquid and solid, from least to most dense. A fifth, the Bose-Einstein condensate, can only exist in temperatures approaching absolute zero. It has limited applications in chemistry.
Gases are made up of atoms and/or molecules that are freely moving and therefore have no definite shape. They morph uniformly to the shape of the container that they are in. If the container is not sealed, then the gas can move out. Therefore the volume of the gas is reliant on the temperature and/or pressure throughout the gas or environment. This is observed using the ideal gas laws, which are discussed later.
An important piece of information to know is what an aqueous solution is also. Aqueous solutions are not technically chemical states, but they appear often enough when dealing with stoichiometry and chemistry in general that they should be mentioned.
Acids and Bases
The potential of hydrogen or pH (pronounced /piː.eitʃ/) is a measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing pH with rising alkalinity and decreasing pH with more acidity. The pH scale commonly in use ranges from 0 to 14.
An alkali is sometimes called a "base".
|Orange or apple juice||
|Tea or healthy skin||
|Healthy human saliva||
Mathematically, calculate pH using the following equation:
Mathematically, calculate pOH using the following equation:
Combining (adding) the results of pH with pOH should equal fourteen (14).
Characteristics of acids:
- Aqueous acids can turn blue litmus towards red.
- React with bases and certain metals to form salts.
- Arrhenius' definition of acid: Yields hydrogen ions when dissolved in water.
- The Lewis definition of an acid: Can accept a pair of electrons to form a covalent bond.
- Brønsted-Lowry acid definition: A species that can lose or "donate" a hydrogen ion
- Can have a sour taste.
- Can give one or more than one protons (or simply, H+)
- Electrolytes, yet usually are not ionic compounds
Characteristics of bases:
- Aqueous bases (alkalis) can turn red litmus towards blue.
- React with acids to form salts.
- Arrehenius definition of base: produce OH− ions when dissolved in water.
- Lewis definition of Base: can donate a pair of electrons to form a covalent bond with an acid
- Brønsted-Lowry base definition: A species that can gain or "accept" a hydrogen ion
- Can have a bitter taste.
- Can accept one or more than one protons (or simpler H+)
- Conduct electricity
The difference between bases and alkalis is that alkalis dissolve in water and are considered basic salts of alkaline metals. An example of a base that is not an alkali is ammonia (NH3).
Nomenclature of inorganic chemistry
- Flowers, Paul, Klaus Theopold, Richard Langley, William R. Robinson, Mark Blaser, Simon Bott, Donald Carpenetti, Andrew Eklund, Emad El-Giar, Don Frantz, Paul Hooker, George Kaminski, Jennifer Look, Carol Martinez, Troy Milliken, Vicki Moravec, Jason D. Powell, Thomas Sorensen, and Allison Soult. Chemistry. N.p.: n.p., 2015. Chemistry. OpenStax College, Mar. 2015. Web.