CHAPTER 3- INTRODUCTION TO THE PERIODIC TABLE Miss Le- 10/17/14

Pay attention to your notes ;)  Pop quiz at the end!

How did it all start?  1860, Scientists had already discovered 60 elements and determined their atomic masses  Noticed some elements had similar properties and gave a group of similar elements a name  Ex. Coinage metals  Wanted to organize the elements that would show similarities and differences at the same time

Dmitri Mendeleev’s Periodic Table  Russian professor at the University of Petersburg  1869 published a table of elements organized by increasing atomic mass  Listed elements in a vertical column starting with the lightest  Started another column when he reached an element that had similar properties to another element already in the column This way elements with similar properties were in HORIZONTAL rows

Mendeleev Cont.  Later developed an improved version  His contribution:  Showed that the properties of the elements repeat in an orderly way from row to row of the table  This repeated pattern is an example of periodicity in the properties of the elements  Periodicity- the tendency to recur at REGULAR intervals  Ex. Halley’s comet every 76 years, full moon every 28 days, what else?

Mendeleev Cont.  Table was widely accepted because it was, to date, the clearest and most consistent arrangement of the elements  Left blank spaces in the table and undiscovered elements would eventually occupy these spaces  By noting the trends in the properties of known elements, he was able to predict the properties of the undiscovered elements.

Moseley  There was inconsistency with Mendeleev’s prediction of elements and their properties by the way he had organized the periodic table  Moseley solved the problem of the inconsistency between the positions of the elements and their atomic masses  He rearranged the elements by increasing atomic number instead!  Resulted in the structure of the modern periodic table. Thanks, Moseley!

Periodic Law  Atomic number increase by one as you move from element to element across a row  Each row (except the first) begins with a metal and ends with a noble gas  Properties of the elements change in an orderly progression as you move from left ot right  All the trends above illustrate periodicity in the properties of the elements  Periodic Law- the physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number

POP QUIZ 1. How does the modern periodic law differ from Mendeleev’s periodic law? 2. What are the two factors that contributed to the widespread acceptance of Mendeleev’s periodic table?

3.2 Using the Periodic Table  Period- horizontal rows  Group/Family- vertical columns  Groups are numbered from left to right  Ex. Lithium is the first element in group 1 and in period 2  Have a marker handy because we’re going to be coloring today!  Marker- outline instead or coloring

Noble Gases  Please get out your periodic tables  We’ll label as we discover special groups of the periodic table  Group 18 elements are the noble gases  Remember what’s special about them?  Hint: what do their outer most energy levels look like?  They’re generally unreactive because of this  Characteristics of Noble Gases: They’re nonmetals. They’re unreactive because their outermost energy level is completely filled.

Metals  Metals are elements that have luster, conduct heat and electricity, and usually bend without breaking  Metals have one, two, or three valence electrons  Exceptions are tin, lead, and bismuth  All metals are solids at room temp. and most have extremely high melting points  Exception is mercury  Most metal elements are located in groups 3-12

Transition Elements/Metals  Do you have your periodic table handy?  Let’s label the Transition Metals  Groups 3-12  Characteristics of Transitional Metals: Their behavior is less predictable than the main group metals and this is because their atomic structure is more complicated. They also have the characteristics of metals.  Let’s label the main group metals too!

More about Periods  The period number of an element is the same as the number of its outermost energy level!  Recall that valence electrons are located in an element’s outermost energy shell.  Ex. Valence electrons in the second period are in the second energy level  Question: Looking at your periodic tables, what period is Aluminum in? So what energy level is it’s valence electrons located in?

Relationship between Valence Electrons and Chemical Properties  You need to know the relationship between the two.  Elements in the same Group have the same number of valence electrons, right?  Well because of this, elements in the same group have similar chemical properties.  Summary: Elements in the same group have similar chemical properties because they have the same number of valence electrons.

Common Names for other Groups  So far we’ve covered what common names for groups?  Transitional metals, main group metals, and noble gases  Group 1- Alkali Metals  Let’s color code this in  Characteristics of the Alkali Metals: They are very reactive metals. They have only ONE electron in their outer shell so they’re ready to lose that one electron to other elements. They’re metals so they have characteristics of metals too!

Common Names for other Groups Cont.  Group 2- Alkaline Earth Metals  Color code and label this  Characteristics: They’re very reactive. They also have characteristics of metals.

Hey- What about the staircase from yesterday?  The stair-step line distinguishes metals from non- metals! It’s a famous stair-step line ;)  Let’s label the non-metals on our table  Notice there are multiple common named groups that fall under “non-metals” and the same goes for the metals.

Common Names for other Groups Cont.  Metalloids- Boron, silicon, germanium, arsenic, antimony, tellurium, and polonium  They are found along the stair-step line because they’re special! They have properties of both metals AND non-metals.  They carry an electrical charge under special circumstances which makes them useful in computers and calculators.

Metalloids Cont.  Some metalloids such as silicon, germanium, and arsenic are semiconductors.  Semiconductors are elements that does not conduct electricity as well as metal, but conducts slightly better than nonmetals.

Common Named Groups Cont.  Group 17- Halogens  Let’s color code!  Characteristics: They are non-metal elements. Compounds containing halogens are called salts. They have 7 electrons in their outer shells.  Rare Earth Metals  Composed of the Lanthanide Series and Actinide Series  Let’s color code!

Did we miss any?  Yes! We forgot the few elements to the left of the halogens.  This right side of the periodic table consists of the non-metals.  Non-metals consist of the few elements we have categorized or named, the halogens, and the noble gases.  Characteristics: They are not able to conduct electricity or heat very well, are very brittle, have no metallic luster, and don’t reflect light.

Physical States of the Elements  More zoomed in figure of the one on the previous slide on pgs. 90 and 91 of your textbooks  It shows the states of the elements at room temperature.  Notice most are solid, only two elements are liquid, and the gaseous elements are located in the upper- right hand corner (minus hydrogen).

Quiz tomorrow!  Covers material over 3.1 and 3.2  Cannot use the periodic table you’ve color coded.  Be able to tell me key points from 3.1 (how did Mendeleev organize his periodic table? What change did Moseley make?)  Be able to label the common group names on a blank periodic table (don’t have to color code, just outline)  Be able to tell me characteristics of metals vs. nonmetals vs. metalloids.