1. Chapter 2: Chemistry of Life1

2. 2.1 Composition of Matter
Matter – anything that occupies space and has mass
Mass – the quantity of matter an object has
**Mass vs. Weight** 2

3. 2.1 Composition of Matter Atoms Atom – the fundamental unit of matter
Components –
Nucleus – central core, most of the mass, consists of proton and neutron
Proton – positive electrical charge
Neutron – no electrical charge
Electrons – negative electrical charge (move around outside of the nucleus)
Overall charge of atom = 0 (protons and electrons cancel each other out) 3

4. 2.1 Composition of Matter 4

5. 2.1 Composition of Matter Elements
Elements – substances that cannot be broken down chemically
Atomic number = # of protons in an atom
Example – carbon – each atom of carbon has 6 protons so the atomic # is 6
Isotopes – atoms of the same element that differ in the number of neutrons
Mass number – sum of protons and neutrons in an atom
Example - 5

6. 2.1 Composition of Matter
Radioisotopes – isotopes in which the nucleus is unstable and tends to release particles or radiant energy or both
Can help determine age of fossils
Can help trace movement of chemicals through organisms 6

7. 2.1 Composition of Matter Compounds
Compounds – consist of atoms of 2 or more elements that are joined by a chemical bond
Compounds often times have different properties than the elements within the compound had when by themselves:
Sodium Chlorine Sodium Chloride 7

8. Sodium chloride (NaCl)
2.1 Composition of Matter
Two Bond Types
Ionic Bonds – electrons move from one atom to another to form a bond
Example – table salt – NaCl – sodium loses and electron and chlorine gains an electron
Transfer of electron
Na Sodium atom
Cl Chlorine atom
Na+ Sodium ion
Cl– Chloride ion
Sodium chloride (NaCl) Na Cl + – 8

9. 2.1 Composition of Matter
Covalent Bonds – electrons are shard one or more pairs of electrons
Example – methane – CH4 – electrons are shared in the outer electron shell: 9