1. The Chemistry of Life: The Nature of Matter
Essential Question: What are the parts of the atom?
HW: Atoms worksheet

2. Matter is Made of Atoms
Atom— smallest unit of matter that cannot be broken down by chemical means
Made up of subatomic particles
protons
neutrons
electrons

3. Elements Are the Simplest Pure Substances
Elements—substance made of only one kind of atom
Elements are represented by a one- or two-letter symbol.

4. Elements
The number of protons in an atom of an element is the element's atomic number.
Is also the number of electrons
Atomic weight (mass) is equal to the number of protons and neutrons

5. Isotopes
Atoms of an element that contain a different number of neutrons
Identified by their mass numbers

6. Elements and Isotopes Radioactive Isotopes
Their nuclei are unstable and break down at a constant rate over time, releasing energy
Although the radiation these isotopes give off can be dangerous, they have important scientific and practical uses.

7. Elements and Isotopes Radioactive isotopes can be used:
to determine the ages of rocks and fossils.
to treat cancer.
to kill bacteria that cause food to spoil.
as labels or “tracers” to follow the movement of substances within an organism.
BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003

8. Atoms Can Bond Together
Compounds linked together by chemical bonds
Covalent
Non-polar
Polar
Ionic
Hydrogen
Van der Waals interactions
Bond Strength

9. Covalent Bonding Valence electrons are shared by atoms
Sharing electrons means that the moving electrons actually travel in the orbitals of both atoms.

10. Ionic Bonding
High electronegativity difference strips valence electrons away from another atom
Electron transfer creates ions (charged atoms)
Cation (positive ion)
Anion (negative ion)
Na+
Cl–
BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003