What is Chlorine? - Atoms - Quatr.us
Quatr.us answers questions
Upgrade /Log in
Options /Log out
Print
About
Africa
Egypt
Mesopotamia
Early Europe
Greece
Rome
China
India
Central Asia
Medieval
Islamic Empire
Native Americans
S./Central America
American History
Biology
Chemistry
Geology
Math
Physics
Weather
Food
Judaism
Christianity
Home

What is Chlorine?

Chlorine atom
Diagram of a chlorine atom

Chlorine is an atom that has 17 protons and usually either 18 or 20 neutrons in its nucleus and 17 electrons circling around its nucleus. Chlorine atoms, like other light atoms such as oxygen, form inside stars and scatter into space when the star becomes a supernova.

On earth, chlorine forms molecules of two chlorine atoms. It is a pale green gas. Chlorine atoms have two electrons in the inner ring, then eight electrons in the second ring, then seven electrons in their outer ring. This means that they are not stable, but they only need to add one electron to the outer ring to fill it up, and then the chlorine atom will be stable.


Video shows what happens when you mix chlorine and sodium.

Because of this missing electron, chlorine atoms join up easily with any atom that has one extra electron. Sodium is the most common example of this, and both in space and on earth sodium and chlorine atoms often join together (with the help of water) - that makes molecules of salt.

Chlorine also mixes easily with water, forming an acid molecule made of hydrogen, oxygen, and chlorine atoms. This is the main ingredient of bleach, and we use it to kill bacteria in water, to make it safe to swim in and to drink. Chlorinated water kills bacteria because it breaks down into chlorine and oxygen. Both the chlorine and the oxygen need more electrons and join easily with other atoms. When they hit a bacterium, they join up with some of the atoms of the lipid membrane of the bacterium cell. Then the lipid membrane leaks. It can't keep the cytoplasm inside the cell anymore, and the cell dies.

Learn by doing - Swimming pools and bread mold
More about salt
Salt in human history

Bibliography and further reading:

Salt
Atoms
Chemistry
Quatr.us home


Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

Help support Quatr.us!

Quatr.us (formerly "History for Kids") is entirely supported by your generous donations and by our sponsors. Most donors give about $10. Can you give $10 today to keep this site running? Or give $50 to sponsor a page?

Now that the weather's nice, try some of these outdoor activities! How about bicycle polo, or archery for a Medieval Islam day? Or kite flying or making a compass for a day in Medieval China? How about making a shaduf for a day in Ancient Egypt? Holding an Ancient Greek Olympic Games or a medieval European tournament? Building a Native American wickiup?