Atoms and Molecules

Everything in the world is made out of tiny particles called atoms.

Understanding atoms will help us understand DNA.

Periodic Table of Elements

Atoms are made up of three parts.

Protons have a positive charge.

Neutrons have a neutral charge.

Electrons have a negative charge.

Atom’s parts

Protons +

Neutrons |

Electrons -

-

Particles that have the same charge repel one

another.

++

-

Particles that have a positive charge are attracted to particles

that have a negative charge.

-+

Particles that have different charges attract

one another.

Atoms & Molecules

Molecules are made of atoms that stick together

Carbon atom

Hydrogen atom

Balanced ChargesMost atoms and molecules have an equal number of protons and electrons making them neutrally charged overall.

Some molecules have an uneven distribution of electrons, making them polar - they are positive at one end and negative at the other.

Polymers•Polymers are very long molecules created

by units repeating in a long chain.

•Some polymers are made up of all the same kind of building blocks, and others are made up of several different kinds of blocks.

DNADNA is a long molecule or polymer!

It is made out of repeating units called nucleotides or base-pairs.

A single human DNA molecule contains about 3 billion base pairs, which is about 10 times the population of the U.S. (300 million people) or about half the population of the entire world (6.7 billion people)

Atoms, molecules, polymers, and DNA are very, very tiny.

They are so small you cannot see them even with most microscopes.

Next: Bonding