1. Unit 3 – Chemical Periodicity

2. Elements & Atoms Element-a pure substance that has one kind of atom  The periodic table lists all the different elements that are either found in nature or prepared in the laboratory synthetically  Atom-the smallest particle of matter  Example of an element is hydrogen. It contains only hydrogen atoms.

3.  PERIODIC TABLE: an arrangement of elements organized with respect to similar traits shared by different elements Definition

4. Development of the PT

5. "...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained.” Dmitri Mendeleev (1869)- First published periodic table Development of the Periodic Table

6.  Arranged in rows (periods) of increasing mass Development of the Periodic Table MASS

7.  Arranged in columns (groups or families) by similarities in physical and chemical properties Development of the Periodic Table

8.  Most important feature: Holes were left in the table to allow for the discovery of new elements Development of the Periodic Table

9.  Mendeleev predicted the discovery of germanium (which he called eka-silicon) as an element with an atomic weight between that of zinc and arsenic, but with chemical properties similar to those of silicon. Development of the Periodic Table

10. Henry Moseley (1913) - Modified into the modern PT  Arranged in rows (periods) of increasing Atomic Number  Arranged in columns (groups or families) by similarities of physical and chemical properties Development of the Periodic Table

11.  The Periodic Law: Chemical and physical properties of elements are periodic functions of their atomic numbers; properties of the elements occur at repeated intervals called periods. Development of the Periodic Table

12. Organization of the PT

13.  The PT lists each element in order of their atomic number  Elements are classified into three major categories based upon their properties: metals, nonmetals, and metalloids Organizing the Periodic Table

14. Metals

15. METALS: located on the left side of the PT (exception of H, which is a nonmetal)  Most elements are metals (~80%)  Good conductors of heat and electricity  Lustrous (shiny)  Solids at room temperature (except Hg)  Ductile and malleable Metals

16. Nonmetals

17. NONMETALS: located on the right side of the PT  Greater variation in physical properties among nonmetals than metals.  Some are solids, bromine is a liquid, but most are gases at room temperature  Do not conduct electricity  Good insulators  Dull and Brittle Nonmetals

18. Metalloids

19. METALLOIDS: indicated by the BOLD “staircase” B, Si, Ge, As, Sb, Te, At  Properties of both metals and nonmetals  Semiconductors Metalloids

20. GROUPS – vertical columns containing elements with similar properties.  There are 18 groups  Groups are also called families due to their similar properties Organizing the PT

21.  The groups are numbered 1-18 with Group 1 being on the far left and Group 18 being on the far right of the periodic table. Organizing the PT 1 18

22. Groups may also be numbered using Roman Numerals Groups may also be numbered using Roman Numerals  “A elements” referring to the Main Group or Representative Elements  “B elements” referring to the referring to the Transition Metals Transition Metals Organizing the PT

23. PERIODS – horizontal rows on the periodic table; each period represents an exact grouping of elements  There are 7 periods  They are simply numbered 1-7 Organizing the PT