Fundamentals of chemistry

Subject classification: this is a chemistry resource.

< Wikiversity:School 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, inorganic nomenclature and chemical bonding.

Chemical Elements are fundamental ingredients of all matter in existence which can be combined in a reaction to create a chemical substance. Each chemical element in the universe has unique properties that distinguish it from all of the other chemical elements. They cannot be chemically interconverted or broken down into simpler substances and are the primary constituents of matter.

Chemical elements are usually notated with the symbol

^M_ZE

Where,

E is the element name

Z the Atomic Number

M the element's mass

For example, Hydrogen is notated by

¹₁H

The periodic table groups the elements by properties. For its history, see 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. Print or order a hard copy of the periodic table for easy access and reference.

In the table, each box contains one element and additional information. For hydrogen, 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.

The elements are organized in rows and columns. 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.

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 have mixed properties, but there are specific patterns.

Electrons are negatively charged subatomic particles that "orbit" 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.

Chemical compounds are pure substances composed of only one type of molecule (two or more atoms held together in a fixed ratio by Chemical bonds). The chemical compound generally has different properties than those of its constituent elements. The name of a chemical compound is usually identical to the name of the molecule that makes up the compound (such as Carbon Dioxide), but some compounds also have "common names" by which the substances are known outside of scientific discussion. For example, sodium bicarbonate is commonly known as "baking soda."

Also see Dalton. The main points of Dalton's atomic theory are:

1. Elements are made of extremely small particles called atoms.
2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3. Atoms cannot be subdivided, created, or destroyed.
4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged.

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.

${\displaystyle NaCl}$

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.

${\displaystyle Cl_{2}}$

Chemical formula is used to represent a chemical compound . For example

• Water is ${\displaystyle H_{2}O}$
• Ozone is ${\displaystyle O_{3}}$
• Salt is ${\displaystyle NaCl}$

A chemical bond is a lasting attraction between atoms that enables the formation of chemical compounds

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.

${\displaystyle Na+Cl}$ → ${\displaystyle NaCl}$

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.

${\displaystyle Cl+Cl}$ → ${\displaystyle Cl_{2}}$

• Oxidation bonding
• Ionic bonding
• Covalent bonding

A chemical reaction is an interaction between chemical subtances to form new substances. For example, an oxidization of a metal, or a de-oxidization of an oxidized metal.

The oxidization of a metal like copper (Cu) to create oxidized copper can be expressed as chemical equation as shown below:

${\displaystyle Cu+O_{2}=CuO_{2}}$

Ionization describes the interaction between a metal and an acid to form ionized opposite polarity metals.

${\displaystyle Cu+H_{2}SO_{4}=CuSO_{4}^{-}+2H^{+2}}$

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:

${\displaystyle {\ce {2H_{2}(g)+O_{2}(g)\rightarrow 2H_{2}O(\ell )}}}$

On the left side of the arrow, you can see two compounds represented. These are the reactants, the chemical species that rearrange to give the product, 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.

The (g) and (l) or state symbols represent what physical state of chemical species during the reaction. (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.

The coefficients in front of the molecules like H₂O and the H₂ represent the simplest whole number ratio the substance amount 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.

As a more complex example, the concentration of nitrogen oxides (i.e., ${\displaystyle \color {Blue}{\ce {NO}}_{x}}$) in the flue gas from an industrial furnace can be converted to a mass flow rate expressed in grams per hour (i.e., g/h) of ${\displaystyle {\ce {NO}}_{x}}$ by using the following information as shown below:

NOx concentration

= 10 parts per million by volume = 10 ppmv = 10 volumes/10⁶ volumes

NOx molar mass

= 46 kg/kgmol (sometimes also expressed as 46 kg/kmol)

Flow rate of flue gas

= 20 cubic meters per minute = 20 m³/min

The flue gas exits the furnace at 0 °C temperature and 101.325 kPa absolute pressure.

The molar volume of a gas at 0 °C temperature and 101.325 kPa is 22.414 m³/kgmol.

${\displaystyle {\frac {10\ {\cancel {\mathrm {m} ^{3}\ {\ce {NO}}_{x}}}}{10^{6}\ {\cancel {\mathrm {m} ^{3}\ {\text{gas}}}}}}\times {\frac {20\ {\cancel {\mathrm {m} ^{3}\ {\ce {gas}}}}}{1\ {\cancel {\text{minute}}}}}\times {\frac {60\ {\cancel {\text{minute}}}}{1{\text{hour}}}}\times {\frac {1\ {\cancel {\mathrm {kg\cdot mol\ NO} _{x}}}}{22.414\ {\cancel {\mathrm {m} ^{3}\ {\ce {NO}}_{x}}}}}\times {\frac {46\ {\cancel {\mathrm {kg} }}{\ce {NO}}_{x}}{1\ {\cancel {\mathrm {kg\cdot mol\ NO} _{x}}}}}\times {\frac {1000\mathrm {g} }{1{\cancel {\mathrm {kg} }}}}=24.63\ {\frac {\mathrm {g\ NO} _{x}}{\text{hour}}}}$

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. A substance dissolved in water is in indicated by (aq). 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.

Ethyne (C₂H₂) is added to oxygen gas (O₂) to yield carbon dioxide (CO₂) and water (H₂O). This reaction could be written as follows:

Unbalanced equation

${\displaystyle C_{2}H_{2}(g)+O_{2}(g)\to CO_{2}(g)+H_{2}O(l)}$

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

${\displaystyle 2C_{2}H_{2}(g)+5O_{2}(g)\to 4CO_{2}(g)+2H_{2}O(l)}$

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

${\displaystyle C_{2}H_{2}(g)+{\color {Red}O_{3}(g)}\ \to {\color {Red}C_{2}O_{2}(g)}+H_{2}O(l)}$

By changing the subscripts you are changing the chemicals involved in the reaction. In the above, ${\displaystyle O_{3}}$ is ozone, not normal oxygen, and ${\displaystyle C_{2}O_{2}}$ is not a stable compound. A small change in the subscripts and makeup of an individual compound yields a whole different set of properties.

We usually learn that there are four fundamental states of matter,

1. Plasma
2. Gas
3. Liquid
4. Solid

However, physics research suggests other states of matter as well (like the Bose-Einstein condensate), but this is usually taken as a coarse starting point.

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.

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".

The pH is calculated by

${\displaystyle pH=-\log[H^{+}]}$A similar measure, called the pOH is defined as

${\displaystyle pOH=-\log[OH^{-}]}$

Their sum is

${\displaystyle pH+pOH=14}$

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).

• 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.

• Acids and Bases
• The School of Chemistry