The Chemistry of Life: Elements & Atoms Unit 3 The Life of a Cell Ch. 7 /Sec. 7.1

Everything (whether it is a rock, robot, or flower) is made of substances called elements. 1. Element: A substance that cannot be broken down into simpler substances

Periodic table (Appendix A pg. A-9) *1-92: elements found in nature (exceptions 43 & 61) *93-above: elements are synthetic - manmade *Each element is abbreviated by a 1 or 2 letter symbol Ex: C- _____ Fe- _____ Pb- _____

2. Trace elements: Present in very small amounts Ex: Iron (in hemoglobin-makes red blood cells) & Magnesium (builds bones, make proteins, release energy, regulate body temp.) - Both play a vital role in maintaining healthy cells *Elements are made up of Atoms!

3. Atom: The smallest particle of an element that has thecharacteristics of that element. 4. Nucleus: The center of an atom; contains protons & neutrons 5. Protons: + charged particles; located in nucleus 6. Neutrons: 0, neutral, or no charge; located in nucleus

7. Electron: Have a negative (-) charge; located around outside of nucleus Ex: Think of a fan An electron cloud is the space around the atoms nucleus that is occupied by these fast-moving electrons They travel around the nucleus in certain regions known as energy levels.

1st level – max of 2 electrons 2nd level – max of 8 electrons 3rd level – max of 18 electrons Ex: O2 8. Isotopes: Atoms of the same element that have different number of neutrons. Ex: carbon – most contain 6, some have 7 or 8