1. Chapter 2: The Chemistry of Life
Section 2-1: Introduction of Chemistry

2. Explain concepts about the structure and properties of matter 3.4.10A
Section Objective
Explain concepts about the structure and properties of matter
3.4.10A

3. What is an atom? An atom is very small! Consists of:
Nucleus – center of the atom
Protons (p+): subatomic particles with a positive (+) charge.
Neutrons (no): subatomic particles with no charge – neutral.
Both have about the same mass = 1 atomic mass unit (1 amu)

4. What is an atom? Consists of: (cont.)
Electron Cloud – outside the nucleus.
Electrons (e-): subatomic particles with a negative (-) charge.
Electrons move in pathways called orbitals or shells.
Mass of an electron is negligible.

5. What is an atom?
Key difference between atoms of different elements is the number of protons and electrons they contain.
Atoms have equal numbers of protons and electrons, so atoms are electrically neutral.

6. Opposites Attract
The (+) charge of the nucleus attracts and holds the negatively charged electrons in their orbitals.

7. What is an element?
A chemical element is a substance that cannot be broken down into any other substance.
The smallest unit of of a chemical element is a particle called the atom.

8. What is an element? 96 naturally occurring elements.
20 elements have been artificially produced in labs.
116 elements total to date