The Periodic Table of Elements and Atom Types I. Organization of the Periodic Table A. periodic law – properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number.

B. Elements are arranged in periods and groups 1. period – a horizontal row of the elements in the periodic table a. another name for periods are valences

2. Every atom has valence electrons a. Electrons are arranged in energy levels. b. valence electron – an electron in the outermost energy level of an atom i. Each energy level can hold only a specific number of electrons ii. Electrons start at the energy level closest to the nucleus and fill up one energy level after another.

B. Elements are arranged in periods and groups 1. period – a horizontal row of the elements in the periodic table a. Another name for periods are rows b. Each period has a number, which refers to how many energy levels are in that element.

2. group (family) – a vertical column of the elements in the periodic table a. Groups of elements in the periodic table, have similar properties b. Valence electrons largely effect chemical and physical properties. c. Elements in the same group have the same number of valence electrons.

II. Ions!!! A. Ion – an atom that has lost or gained one or more electrons and therefore has a net electric charge.

E. Atoms have no overall charge 1. An un-reacted, elemental atom has the same number of protons as electrons 2. Each proton has 1 positive charge and each electron has 1 negative charge. 3. Positive charges and negative charges cancel each other out. 2 protons = + 2 charges 2 neutrons = 0 charge + 2 electrons = - 2 charges 0 charge 7 protons = + 7 charges 7 neutrons = 0 charge + 7 electrons = - 7 charges 0 charge

II. Ions!!! A. Ion – an atom that has lost or gained one or more electrons and therefore has a net electric charge. B. Ionization – the process of adding or losing one or more electrons from an atom C. Atoms want all of their energy levels to be full. Adding or losing electrons helps this to happen.

C. Ions have charge! 1. cation – an ion that has given up one or more electrons a. Cations have more protons than electrons. b. Cations have an overall positive charge. 2. anion – an ion that has gained one or more electrons a. Anions have fewer protons than electrons. b. Anions have an overall negative charge. 11 protons = + 11 charges 12 neutrons = 0 charge + 10 electrons = - 10 charges + 1 charge 17 protons = + 17 charges 18 neutrons = 0 charge + 18 electrons = - 18 charges - 1 charge

III. Differences in atomic structure A. Atomic number 1. atomic number – the number of protons in an atom 2. Each element has its own atomic number.

B. Atomic mass 1. atomic mass – the mass of an atom of a given element 2. The average atomic mass is never a whole number. C. Isotopes!! 1. isotopes – any atoms having the same number of protons but different numbers of neutrons C 1213

2. average atomic mass – the mass of the average atom of a given element b. It reflects number of protons and neutrons in naturally occurring elements. a. Atomic mass unit (amu) – a unit equivalent to 1/12 the mass of a carbon- 12 atom (~1 proton or neutron) 12 protons +12 neutrons 24 amu 12 protons +13 neutrons 25 amu 12 protons +14 neutrons 26 amu 78.65% x 24 amu 10.14% x 25 amu % x 26 amu amu