Organic Chemistry

Projects

Properties of Water

Solutions

Buffers

Organic Chemistry Facts

Elements
Organic Groups
Proteins
Carbohydrates
Lipids
Nucleic Acids

Organic Chemistry Sites

Protein Structure and Function. Univ. Wisco.
Carbohydrate Structure and Function. Texas A&M University.
Lipid Structure and Function. Texas A&M University.
Nucleic Acid Structure. Univ. Wisco.
Atoms, Molecules, Water, pH. Clermont College.
pH Regulation During Excercise. Washington Univ.

References:

Biology, 5th ed.. Campbell, Reece, and Mitchell . Benjamin/Cummings, Publ. 2001.

Chemistry and The Living Organism. Bloomfield, Molly M. John Wiley & Sons. 1977.


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Organic Moleucles


The Elements:

Matter is made up of basic substances called elements. These "bacon-rind" cave formations contain some of the same elements found in your bones, in tap water, and even in air. We usually think of the element oxygen as a gas, but it is also the most common element in rocks. Some elements are used as coloring agents. A substance made from the element cadmium colors paint yellow. A cobalt compound colors porcelain and tile blue. A chromium compound makes rubies red. Other elements have familiar properties and uses. Uranium is radioactive. Mercury is a liquid metal at room temperature. Barium compounds and strontium compounds produce green and red colors in fireworks. Sulfur is a bright yellow solid. Chlorine is a yellowish-green poisonous gas. Lithium is a metal that is explosive and very light. In all, there are 109 known elements. Through observation and experimentation, scientists have agreed on a way to group these elements. The elements are grouped according to their properties.

The Periodic Table of the Elements

You will find out

  • how the alchemists contributed to science;
  • what elements are;
  • how elements are classified in the periodic table
  • how the periodic table is organized;
  • the characteristics of metals and nonmetals..

When you look at the world around you, you see that it is filled with an amazing variety of substances. You see all different shapes, sizes, and colors. Some substances are soft; others are hard. Some are solids, others are liquids, and still others are gases. Long ago the people who sought to answer the question of what matter is made of were called alchemists. Alchemists believed that if they could find the basic unit of matter, or primary matter as they called it, they could do wonderful things. With primary matter they thought they could change ordinary metals into gold and ordinary water into a liquid that would stop the aging process. In the course of their search, they tested all known substances. They burned them, boiled them, crushed them, filtered them, and mixed them. Although the alchemists never found the primary matter, they did help to establish the scientific method used today. They realized the importance of clearly stating a problem, forming a hypothesis, and testing the hypothesis through a controlled experiment. The alchemists showed that perseverance is needed in science. Sometimes hypotheses must be revised and retested hundreds of times before conclusions can be formed. The work of the alchemists set the stage for eighteenth and nineteenth-century scientists who showed that all matter is composed of basic substances called elements. Elements are substances that cannot be chemically broken down into simpler substances.

The elements in your body. (Adapted From Cummings et al. Table 2.1, Biology. 2001.)

More than a hundred different elements have been discovered so far. The elements that occur in nature are called the natural elements. Some natural elements are oxygen, calcium, nitrogen, and zinc. Synthetic elements have been made by scientists in the laboratory. When scientists discovered a synthetic element, they had the privilege of naming it. Californium was discovered at the University of Berkeley in California. Plutonium was named after the planet Pluto.

For many years scientists tried to organize elements with similar properties into groups. The first person to sensibly group elements in a way that could be used to make predictions was Dmitri Mendeleev, a Russian scientist. In 1869, Mendeleev published a table of elements arranged according to properties. An updated version of his table, called the Periodic Table, can be found in your planners.

When you study the Periodic Table, you will see one or two letters in the center of each box. This is the symbol, or abbreviation, for the element's name. There is a number in the upper right corner of each box: This number is called the atomic number of the element. In each horizontal row, the atomic numbers of the elements increase as you read from left to right. The horizontal rows are called periods. Elements with similar properties are placed in vertical rows on the periodic table. The vertical columns are called groups or families. Each group is named by the numeral you see at the top of each vertical column. Thus, group 1 includes the elements hydrogen, lithium, sodium, potassium, rubidium, cesium, and francium. Group 15 includes nitrogen, phosphorus, arsenic, antimony, and bismuth. For convenience, two subfamilies are separated out and displayed below the main body of the periodic table. These families are referred to as the lanthanides and the actinides.

The periodic table has a wealth of information about the elements, including whether the element is a metal or a nonmetal, and its usual state. The dark line that looks like steps on the right side of the table separates the metals and nonmetals. The elements to the left of the line are metals. Metals are good conductors of heat and electricity, are shiny, can be pounded into different shapes, and can be drawn into wires. Nonmetals are found to the right of the line. Nonmetals are usually poor conductors of heat and electricity, are dull, and break or shatter instead of bend. The division between metals and nonmetals is not as sharp as the dark line would show. The elements on either side of the line have properties of both metals and nonmetals. These elements are called metalloids. The color of the element's symbol on the periodic table in this book tells you the physical state of the element at room temperature. Mercury, atomic number 80, and bromine, atomic number 35, are liquids. Eleven of the elements, including oxygen, atomic number 8, and chlorine, atomic number 17, are gases. The remainder of the elements are solids.

Information from the Periodic Table

Element

Symbol

Atomic Number

Atomic Mass Number

Group

Metal, Nonmetal, or Metalloid

State under Standard Conditions

Hydrogen

H

1

1

1

Nonmetal

Gas

calcium

Ca

20

40

2

Metal

Solid

silicon

Si

14

28

14

Metalloid

Solid

Chromium

Cr

24

52

6

Metal

Solid

bromine

Br

35

80

17

Nonmetal

Liquid

silver

Ag

47

108

11

Metal

Solid

xenon

Xe

54

131

18

Nonmetal

Gas

The periodic table has proved to be a useful way to group the elements. It is amazing that when Mendeleev first set up the periodic table there were only 66 known elements. Yet his arrangement laid the foundation for a table that can still be used today when 109 elements are known! Mendeleev's purpose in organizing the elements into a table was to enable him to make predictions about their behavior. Mendeleev was also able to predict the existence of certain elements before they were discovered. Mendeleev was so sure that the elements later named germanium, gallium, and scandium existed that he left spaces for them on his table. They were later discovered-and proved that he was right!

Organic Elements

The organic elements are those elements commonly found in living organisms. They compose the building blocks for our organic molecules, like proteins, sugars, fats, and genetic material. These elements also consist of ions needed for common organic processes, like nerve cells communicating with each other, moving muscles, or releasing adrenaline. The most common organic elements are oxygen, carbon, hydrogen and nitrogen. Together, these atoms form 96.3% of the Human body by weight. The following table shows the most commonly occurring natural elements found in the Human Body.

Naturally Occurring Elements in the Human Body

Symbol

Element

Atomic Number

% Human Body Weight

O

Oxygen

8

65.0

C

Carbon

6

18.5

H

Hydrogen

1

9.5

N

Nitrogen

7

3.3

Ca

Calcium

20

1.5

P

Phosphorus

15

1.0

K

Potassium

19

0.4

S

Sulfur

16

0.3

Na

Sodium

11

0.2

Cl

Chlorine

17

0.2

Mg

Magnesium

12

0.1

From Cummings et al. Table 2.1, Biology. 2001.

Of the naturally occurring elements, carbon is probably the most important organic element. On the Periodic Table, carbon is the first member of Group IV. Group IV members have four valence electrons, so they can become stable by either losing or gaining four electrons. Other groups will either lose or gain electrons, but with Group IV's flexibility, these atoms, particularly carbon, tend to share electrons.

Sharing electrons forms strong covalent bonds between atoms. Group IV atoms can form four covalent bonds, one for each electron. Remember that electrons have a negative charge. So these electrons repel each other. For the bonds to become stable, they must lie equal distance from each other. This arrangement forms a tetrahedron. A tetrahedron is like a camera tripod, with the legs and camera stand having equal lengths. Of the Group IV atoms, carbon forms the most stable covalent bonds.

Carbon is also unique in that it can form very stable bonds with other carbon atoms. It is this nature that forms the foundation for organic molecules. Proteins, sugars, fats and genetic material is made with a carbon backbone, upon which other elements are attached.