Regents Chemistry Agenda Monday 10/25/04 Return all papers Review pg. 119 – 120 HW assignment Review HW assignment from last Thursday Outline for Notebook for Periodic Table Unit Tomorrow: Summary review of PT

Summary of PT Mendeleev arranged the first Periodic Table according to atomic mass But, we now arrange the table by increasing Atomic Mass

Arrangement The periodic table is arranged according to Groups (families) in columns and Periods in rows Elements of the same group have similar chemical properties because they have the same number of valence electrons

Groups (Families) Some groups are named: Group 1 : Alkali Metals Group 2 : Alkaline Earth metals Group 17 : Halogens Group 18 : Noble Gases

Practice Problem Which of the following elements have similar chemical properties Which of the following is an Alkaline Earth Metal? a)Nac) Li b)Ned) F a)Lic) Ar b)Mgd) Cu

Key to Table Atomic Number - # of protons in an atom of an element: defines an element! Atomic Mass - # of protons + Neutrons Oxidation States - #s in upper right hand corner that describe how an atom behaves when it is in a bond C

Practice What element has 10 protons? How do you determine how many neutrons are in an atom? Neon Atomic Mass – Atomic Number = # of protons

Average Atomic Mass The Atomic mass number on the periodic table is actually the average of all known isotopes We can fins this by multiplying the mass number of each element x it’s percent abundance and then adding them up

Practice Find the Average Atomic Mass of the following:

Isotopes In an electrically neutral atom, the number of protons equals the number of electrons Positive protons + negative electrons = 0 overall charge But two atoms of the same element can have a different # of neutrons…

Isotopes Atoms of the same element that have a different # of neutrons Carbon – 12 and Carbon – 14 But remember they have the same # of protons! CC

Practice Problems Which of the following are isotopes of each other? How many neutrons are in the following? Lithium – 8 Sodium - 23 a)Nitrogen – 13c) Carbon – 12 b)Oxygen – 15d) Nitrogen - 14

Divisions Periodic Table is divided into Metals, Metalloids and nonmetals Metals: are most of the elements of the table : are lustrous, malleable, ductile and good conductors of electricity Nonmetals: on the right side of the staircase : are dull, brittle, poor conductors Metalloids: on the staircase : Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium

Practice Problem Which of the following is a good conductor of electricity? Which of the following is a Noble Gas? a)Fc) Cu b)Ard) C a)Cac) Fe b)Ned) B

Natural State of Elements Elements can be found: Monoatomic: one atom alone Diatomic: two atoms of the same element together Most elements are found combined with other elements as compounds in nature Most are solids, some are gases, bromine and mercury are the only liquids Most reactive elements are in groups 1, 17, 18

Practice Problems Which of the following is naturally a diatomic gas? Which of the following is a liquid at room temperature? a)Argonc) Copper b)Neond) Oxygen a)Heliumc) Bromine b)Hydrogend) Mercury

Trends on the Table Ionization Energy – increases from left to right and up the columns Atomic Radii – increases from right to left and down columns Ionic Radii – depends on if the atom looses or gains electrons Electronegativity – increases from left to right and up the columns Reactivity – Groups 1,2 and 17 along with oxygen are most reactive

Trends Electronegativity and ionization energy Atomic Radius

Practice Problems Which of the following is the most electronegative? Which of the following has the smallest atomic radius? a)Lic) N b)Cd) O a)Bec) Mg b)Cad) Sr END