Organic Compounds (7.6A)

Organic Compounds (7.6A)

Student Expectation

The student is expected to identify that organic compounds contain carbon and other elements such as hydrogen, oxygen, phosphorus, nitrogen, or sulfur.

Key Concepts

• Key Concept 1: Compounds that contain carbon are called organic compounds.
• Key Concept 2: Many organic compounds often contain hydrogen, oxygen, phosphorus, nitrogen and sulfur, in addition to carbon.
• Key Concept 3: All living things are made up of organic compounds.

Elements are pure substances that cannot be broken down into any other substances by chemical or physical means. Elements make up all of the different kinds of matter in the universe either as single elements or in combination with other elements. The Periodic Table of elements is a way of organizing all known elements by their physical and chemical properties. An element is identified by its specific chemical and physical properties. Each element has a chemical symbol, which is usually one or two letters representing the element. If the symbol for an element is a single letter, then the letter is always capitalized. If the symbol is two letters, then the first letter is always capitalized and the second letter is lowercase. The symbols for each element are shown on the Periodic Table and are used to represent elements in chemical formulas and equations. Chemical symbols consist of letters of the Latin alphabet, although they are intended to be used by people of all languages. Examples of elements with symbols based on Latin names are copper (Cu- Cuprum), gold (Au – Aurum), and silver (Ag – Argentum).

Although there are a little more than 100 different elements in the world, only a small number comprise a majority of the different systems on Earth. The elements that make up rocks and minerals of solid Earth include silicon, oxygen, iron, magnesium, and other trace amounts of various elements. Living organisms are composed primarily of carbon, oxygen, and hydrogen. Other elements in living matter include calcium, nitrogen, phosphorus, potassium, and trace amounts of other elements. Water is made up of hydrogen and oxygen. The oceans also contain salt, made up of sodium and chlorine. The atmosphere is mostly made up of the element nitrogen, existing in diatomic form (N2). It also includes oxygen, carbon (in carbon dioxide) and a small amount of other elements. Even though most of the other elements do occur naturally, they do so in very small amounts compared to the limited number of elements making up the majority of Earth’s systems. The most abundant elements on Earth are located within the first twenty elements on the Periodic Table.

Elements consist of one type of atom distinguished by its atomic number which represents the number of protons in its nucleus. An atom that has a different number of protons represents a completely different element. Only a few elements exist in nature as pure elements. Examples include nitrogen gas (N2), oxygen gas (O2), gold (Au), carbon (C), silver (Ag), and copper (Cu). Many metals exist in pure element form. Most matter consists of elements combined with other elements in a set ratio or proportion called compounds. For example, water is a compound made of the elements hydrogen and oxygen. The ratio of these elements is two hydrogen atoms and one oxygen atom for each molecule of the compound water. Carbon dioxide gas is another example of a compound. Any sample of carbon dioxide is always made of part carbon to two parts oxygen (CO2). Salt, sodium chloride is made of one part sodium to one part chlorine (NaCl).

When elements are combined to make a compound, the new substance has properties different from those of the original elements. For example, table salt is made of two elements, sodium and chlorine. The properties of table salt do not represent the properties of the individual elements. Sodium in element form is a highly reactive metal and chlorine is usually a yellow-green gas in its natural state. When combined to make salt, the properties of the compound are considerably different.

Organic compounds are compounds that contain one or more atoms of carbon covalently bonded to atoms of other elements, most notably hydrogen, oxygen, phosphorus, nitrogen, or sulfur. However, not all carbon-containing compounds are classified are organic. Inorganic carbon compounds include carbon dioxide, carbon monoxide, metal cyanides, carbonates and bicarbonates of metal ions, and a few others.

There are many organic compounds and the large number is possible because of carbon’s ability to form strong covalent bonds to each other in addition to holding the atoms of other nonmetals strongly. The properties of carbon also allow organic compounds to have hundreds or even thousands of chains of carbon atoms (polymers). In addition, isomers, compounds with similar molecular structures but different arrangements, increase the number of organic compounds.

Many organic compounds are important for living organisms. Examples of organic compounds can be found in carbohydrates (which include polysaccharides), lipids, nucleic acids (including DNA and RNA as polymers), vitamins, enzymes, and amino acids (monomer building blocks of proteins and peptides). Polysaccharides include starches in animals and animals, as well as cellulose in plants. Another organic compound in organisms includes ATP, adenine triphosphate.

Because of the large number of organic compounds, they are classified into groups, based on the structure and number and types of elements present. Major groups of organic compounds include alkanes, aldehydes, alcohols, carboxylic acids, ketones, esters, sugars, cyanides, phenols, sulfides, just to name a few of the thousands of different organic compounds.