Chapter 2: Chemistry of Life 1

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

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

2.1 Composition of Matter 4

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

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

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

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

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