Chapter 6.1

Chapter 6: The Periodic Table

Section 1:Organizing the Elements

Compare early attempts at organizing the elements to the modern periodic table;

Explain how elements are arranged in the modern periodic table; and

Identify three broad classes of elements and their properties.

Students will be able to:

First attempts to organize elements was based on their properties

J.W. Dobereiner organized them into triads◦ Groups of three elements with similar properties◦ Middle element had properties that were between

the other two Example: Cl, Br, I

Organizing the elements...

Dimitri Mendeleev organized elements by increasing atomic mass◦ Saw periodic, repeating pattern of properties◦ Also had holes for undiscovered elements◦ When they were discovered, matched his

predictions

Then-deleev Mendeleev

Predicted two elements between Zn & As

When Ga & Ge discovered, matched his prediction

Periodic law: when elements arranged by increasing atomic number, there is a periodic repetition of their physical and chemical properties ◦ Holds for all elements, unlike Dobereiner ◦ Differs from Mendeleev, who used atomic mass

Now we’re smarter...

Metals Nonmetals Metalloids

Based on their general properties

3 Classes

~80 % of elements Good conductors of heat & electric currents High luster (shiny)

◦ Ability to reflect light Solid at RT

◦ Except Hg (mercury) Ductile—can form wires Malleable—can make thin sheets without

breaking

Metals

Found in the upper right corner. Most are gases at RT

◦ N, O A few are solids

◦ Sulfur & Phosphorus 1 liquid

◦ Br

Nonmetals

Poor conductors◦ Except Carbon

Brittle—will shatter if hit

Nonmetals

Properties of both metals & nonmetals Depends on the conditions Example Silicon

◦ Poor conductor◦ Add small amount of boron—now a good

conductor

Metalloids

Compare early attempts at organizing the elements to the modern periodic table?

Explain how elements are arranged in the modern periodic table?

Identify three broad classes of elements and their properties?

Objectives

Page 160, # 1-7

Homework