Unit 2
Chapter Overview
During this unit, students explore how the atomic structure of each element relates to its placement on the Periodic Table and its various chemical properties. Students further their understanding of periodic trends in chemical families and relate these trends to electron configurations within and between atoms.
Main Ideas
The historic scientific discoveries of the nature of the atom have fundamentally changed scientific understanding of the nature of matter.
How has each historic scientific discovery changed our understanding of the chemical and physical properties of matter and our use of the Periodic Table?
In what ways can the Periodic Table be used to demonstrate chemical and physical patterns?
The arrangement of the elements in the modern Periodic Table system is based on their physical and chemical properties. Analysis of this arrangement reveals similarities among the elements in a chemical family and trends that allow for powerful predictions.
How is the Periodic Table used to identify and explain periodic patterns (trends) among elements?
Misconceptions
Students may not understand the Periodic Table has not always looked like it does now.
Students may not understand the important trends within the Periodic Table.
Students may have difficulty understanding how and why ionization energy and electronegativity vary on the Periodic Table.
Vocabulary
Periodic Table – a table of the chemical elements arranged in order of atomic number
Chemical Family – column of elements in the periodic table with similar chemical properties, also called group, there are 18
Alkali Metals – group 1 of the periodic table, very reactive metals
Alkaline Earth Metals – group 2 of the periodic table, easily reactive metals, only found in compounds in nature
Transition Metals – groups 4-12 in the periodic table, metallic elements
Halogens – group 17 in the periodic table, reactive nonmetals
Noble Gasses – group 18 of the periodic table, nonreactive gasses
Atomic Radius – a measure of the size of an atom of an element from the nucleus to the outer electrons
Ionic Radius – a measure of the size of an ion of an element in a crystal (usually measured by taking half the distance between two nuclei)
Ionization Energy – a chemical property that describes the amount of energy required to remove an electron from an atom
Electron Affinity – amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion
Oxidation Numbers – number assigned to an element in chemical combination that represents the number of electrons lost (or gained, if the number is negative) by an
atom of that element in the compound
Electronegativity – a chemical property that describes the extent to which an atom attracts electrons towards itself; cannot be directly measured
Valence Electrons – electron that is associated with an atom and that can participate in the formation of a chemical bond
Lewis Dot Structure – atomic symbol with dots showing valence electrons
Electron Configuration – the distribution of electrons of an atom or molecule in atomic or molecular orbitals
Aufbau Principle – the configuration (order of filling) of the s, p, d, and f orbitals; electrons fill the lowest energy levels first
Hund’s Rule – electrons fill empty orbitals before they pair up
Octet Rule – elements other than transition metals tend to react so that each atom has eight electrons in its outer (valence) shell, orbitals are full
Pauli Exclusion Principle – electrons in the same orbital and value must have opposite spins
Notes
E-Con and Noble Gas Demo
Other Valuable Resources