CH. 2: Basic Chemistry (pp. 19–34)
Element – a basic substance that cannot be broken down
into simpler substances by normal chemical methods.
There are 92 naturally occurring elements
The Most Abundant Elements in Living Things
1. Oxygen (O) (65%)
2. Carbon (C) (18%)
3. Hydrogen (H) (10%)
4. Nitrogen (N) (3%)
5. Phosphorus (P) (1%)
6. Sulfur (S) (0.25%)
(total approximately 97.25% human weight)
other elements: calcium (Ca), sodium (Na), potassium (K),
chlorine (Cl), magnesium (Me), iron (Fe), iodine (I),
zinc (Zn), etc.
Atom – smallest unit of an element that retains the
properties of that element.
Three Main Subatomic Particles
1. Protons – in nucleus (atomic core); Positively charged.
2. Neutrons – in nucleus; Uncharged
3. Electrons – in constant motion around nucleus;
Negatively charged; much smaller than protons and
neutrons.
