1. CHAPTER 2-1

2. ATOMS Atom –basic unit of matter
Ex. Democritus – breaking a piece of chalk, when is it not chalk anymore? Until atomos “unable to be cut”
An atom is very small. 100 million atoms make up about 1 cm.
1 strand of hair is 1 million atoms wide.

3. ATOMS
Atoms are made of smaller subatomic particles: protons, neutrons, and electrons.
Protons have a positive charge, neutrons have a neutral charge
Together make up nucleus of atom
Electrons are negatively charged and much smaller than protons
Atoms have a neutral charge
** # protons = # electrons

4. ELEMENT Element a pure substance made up of just one type of atom
Elements have a one or two letter symbol
The number of protons equals the atomic number of the element
Atomic number usually on top (whole numbers)

5. ELEMENT
How many more neutrons?
Isotopes - Atoms of one element with different number of neutrons.
Isotopes are identified by their mass number
Isotopes have the same number of protons and electrons
Isotopes have the same chemical properties.
Radioactive isotopes – important for dating and labels to follow the movement of substances within organisms.

6. CHEMICAL COMPOUNDS
Compound - formed by the chemical combination of two or more elements in definite proportions.
Written in shorthand known as a chemical formula
Glucose = C6H12O6

7. CHEMICAL COMPOUNDS
The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.
Ex. Sodium Chloride – Sodium and Chlorine

8. CHEMICAL BONDS
The main types of chemical bonds: ionic bonds and covalent bonds.
Ionic bond - formed when one or more electrons are transferred from one atom to another.
Positively and negatively charged atoms are known as ions.
Salts – metal plus nonmetal

9. CHEMICAL BONDS
Covalent bond - formed when one or more pairs of electrons are shared between two atoms.
Can be a single, double or triple bond

10. CHEMICAL BONDS Molecule - smallest unit of compounds. Ex. Water – H2O
Doesn’t usually share electrons equally between the two atoms
What are molecules made of? Elements

11. CHEMICAL COMPOUNDS
Van der Waals forces - intermolecular interaction in which molecules that are close together have a slight attraction that develops between the oppositely charge regions of nearby molecules.
Ex. Tokay gecko