This document discusses the basic units that make up all matter - atoms. Atoms are composed of protons, neutrons, and electrons. The center of the atom is the nucleus, made up of protons and neutrons, while electrons orbit around the nucleus. Atoms are neutral overall since they contain equal numbers of protons and electrons, which have opposite charges. Elements are pure substances made of one type of atom, with the number of protons defining an element's identity and atomic number. Isotopes are atoms of the same element that differ in their number of neutrons, identified by their mass number, but they have the same chemical properties since they contain the same number of electrons.

1. THE CHEMISTRY
OF LIFE
CHAPTER 2

2. ATOMS
AN ATOM IS THE BASIC
UNIT OF MATTER

3. ATOMS
ATOMS ARE MADE UP OF
PROTONS, NEUTRONS, AND
ELECTRONS

4. ATOMS
PROTONS ARE POSITIVELY CHARGED
PARTICLES
NEUTRONS HAVE NO CHARGE
ELECTRONS ARE NEGATIVELY
CHARGED PARTICLES

5. ATOMS
THE CENTER OF THE ATOM
IS THE NUCLEUS, AND IS
MADE UP OF PROTONS AND
NEUTRONS

6. ATOMS
ELECTRONS, THE
NEGATIVELY CHARGED
PARTICLES, ARE IN
CONSTANT MOTION IN THE
SPACE AROUND THE
NUCLEUS

7. ATOMS

8. ATOMS
ATOMS HAVE AN EQUAL
NUMBER OF PROTONS AND
ELECTRONS, AND HAVE
EQUAL BUT OPPOSITE
CHARGES. ATOMS ARE
THEREFORE NEUTRAL.

9. ELEMENTS
AN ELEMENT IS A PURE SUBSTANCE
THAT CONSISTS OF ONE TYPE OF
ATOM
THERE ARE OVER 100 KNOWN
ELEMENTS, WHILE ONLY ABOUT 24
ARE COMMONLY FOUND IN LIVING
ORGANISMS

10. ELEMENTS
THE NUMBER OF PROTONS IN AN
ATOM OF AN ELEMENT IS THE
ATOMIC NUMBER
FOR EXAMPLE,THE ATOMIC # FOR
CARBON IS 6. CARBON THEREFORE
HAS 6 PROTONS, AND 6 ELECTRONS

11. ISOTOPES
ISOTOPES ARE ATOMS OF
THE SAME ELEMENT THAT
DIFFER IN THE NUMBER OF
NEUTRONS THEY CONTAIN

12. ISOTOPES
THE MASS NUMBER IS THE
SUM OF THE PROTONS AND
NEUTRONS IN AN ATOMS
NUCLEUS

13. ISOTOPES
ISOTOPES ARE IDENTIFIED
BY THEIR MASS NUMBER

14. ISOTOPES
BECAUSE ISOTOPES HAVE
THE SAME NUMBER OF
ELECTRONS, ALL ISOTOPES
OF AN ELEMENT HAVE THE
SAME CHEMICAL
PROPERTIES