Atoms and Molecules
Bonds and Octet Rules
VISUAL AIDSFunctional Groups
QUIZZESPractice Quiz I
Practice Quiz II
Practice Quiz III
Atoms are the basic building blocks of matter, in the same way that bricks are the basic building blocks of a house. Atoms are incredibly small, too small even to be seen with a microscope. There are 9 sextillion atoms (9,000,000,000,000,000,000,000) in a penny.
An atom, magnified approximately 1,000,000,000,000,000,000 times
This is an imaginary construct being used for illustrative purposes.
Atoms can combine with other atoms to form molecules. Molecules always contain more than one atom. Water exists as a molecule, made up of one oxygen atom and two hydrogen atoms.
Molecules can be broken apart into atoms, which are simpler forms of matter. Atoms, however, are among the simplest forms of matter and cannot be broken apart into anything else by ordinary chemical means. Similarly, compounds can be broken down into elements, which are simpler forms of matter; elements cannot be broken down into anything else by ordinary chemical means. If you had a sample of an element, say iron, and divided it an infinite amount of times, you would end up with just a pile of atoms, every one identical to the other.
Representation of atoms in an iron nail
If you had a sample of a compound, like water, and divided it an infinite amount of times, you would end up with a pile of molecules, every one identical to each other. However, you could go a step further and begin to divide the molecules themselves to result in a pile of the different atoms that make up the molecules.
Representation of a water molecule
To summarize, an element, which is matter that cannot be broken down into smaller parts by ordinary chemical means, exists as a collection of atoms. A compound, which is matter that can be broken down into smaller parts, exists as a chemical combination of elements and, in many cases, as a collection of molecules.