1. CHAPTER 2.1 The Nature of Matter
THE CHEMISTRY OF LIFE
CHAPTER 2.1 The Nature of Matter

2. Atoms Basic unit of matter Greek atomos, which means “unable to cut”
Proposed by Democritus 2500 years ago

3. Subatomic Particles Nucleus- held together by strong forces
Protons (+)
Neutrons (0)
Electrons (-)
1/1840th the mass of a proton

4. Elements and Isotopes
Element- pure substance that consists of entirely one atom
Isotopes- atoms of an element with different numbers of neutrons
Because they have the same number of e-, all isotopes of an element have the same chemical properties
Isotopes are identified by their mass numbers
C-12, C-13, C-14
Atomic mass is the weighted average of the isotopes found in nature (abundance)

6. Radioactive Isotopes
Contain unstable nuclei that breakdown at a constant rate over time
Radiation can be used to…
Date rocks and fossils
Treat cancer
Kill bacteria in food
As “tracers”
Can be harmful!

7. Chemical Compounds
A substance by the chemical combination of two or more elements in definite proportions
Properties of compounds are usually different than the elements that make it up
Sodium- silvery soft metal, reacts explosively with cold water
Chlorine- greenish poisonous gas

8. E-dot diagrams and bonds
The electron dot diagrams express the element’s symbol and number of valence electrons available for bonding.
Try these… Na Mg B C P S F Ne He

9. Formation of Ions
When a neutral atom gains/loses electrons, its overall charge becomes + or -
When you gain an electron the ion is known as an anion which is negative.
When you lose an electron the ion is known as a cation which is positive.

10. Ionic Bond- ions Bond formed between two ions by the transfer of electrons

12. Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

13. COVALENT BOND- Molecules Bond formed by the sharing of electrons

14. Covalent Bonds

15. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

16. Van der Waals Forces Weak force of intermolecular attraction
Due to uneven charges that exist in covalent bonding
Helps geckos grip smooth surfaces!