The Periodic Table Chapter 12 Lesson 2 Pages E14 – E21

Objectives Recognize that the elements are organized according to their properties in a chart called the periodic table of the elements. Recognize that there are more than 100 known elements, and each can be identified by its symbol. Observe that elements are grouped into three “classes”: metals, nonmetals, and semimetals.

450 B.C. Greek philosopher Empedocles (ehm PEHD uh kleez)  all matter made up of four elements –Earth –Air –Fire –Water

1600’s English chemist, Robert Boyle, argued earth, air, fire, and water could not be real elements.

1700’s French chemist, Antoine-Laurent Lavoisier\ Made one of the first modern lists of chemical elements

1800’s Many new elements being identified Scientist realizing some elements had similar properties Began organizing elements into families, or groups, with similar properties Still no standardized way of classifying elements

1869 Russian chemist Dmitri Mendeleyev Developed a way to arrange and classify elements

Mendeleyev arrangement FIRST –Listed the elements in order of increasing mass –Noticed a repeating pattern NEXT –Rearranged the list so elements with similar properties would appear in the same columns of his table –He left empty spaces for future elements that were discovered

PERIODIC TABLE A table in which the elements are arranged by their properties The periodic table is standardized –This means scientist all over the world use the same one

Why is the table called periodic? Mendeleyev discovered the properties of elements have a repeating pattern The word periodic means “repeating”

The modern periodic table arranges the elements by their? properties

The Periodic Table Modern periodic table elements are arranged in order of increasing atomic number This means= the number of protons in their nuclei

Understanding the table Each element box: –Lists the atomic number –Chemical symbol (abbreviation of the element’s name, sometimes from Greek or Latin) –Name –Often included is also the mass

Understanding the Table Each Column: –Called a group –They have similar properties –Look at copper (Cu), silver (Ag), and gold (Au) on page E17 –These three elements are all soft, shiny metals

Understanding the Table Horizontal Rows: –Called periods –They have an increasing number of elements –Two rows are pulled out to keep the table from getting to long

Classification of Elements METALS – are usually shiny, can be bent or stretched, and conduct electricity NONMETALS – most are gases. Solid nonmetals are usually dull in color, do not conduct electricity, do not bend or stretch, and break SEMIMETALS – have characteristics of metals and nonmetals

Look at the periodic table page E17 Can you find a pattern of metals, nonmetals, and semimetals in the table? Do you think an element found on the bottom left-hand side of the periodic table is a metal, a semimetal, or a nonmetal? Most metals are found on the lower left-hand side of the table, so I would say probably a metal

Chemical symbols are different colors The color of the symbol tells you if the element is a solid, liquid, or gas at room temperature Most are solids

METALS Properties: –Luster – the ability to reflect light –Bendable by force or heating –Can be stretched or pulled into thin wires –Conduct electricity

Metals Found in your body and foods Bones & teeth  calcium Blood  iron Most metals found in living things combine with other elements in chemical compounds

SEMIMETALS Have properties of both metals and nonmetals Silicon is a semimetal 28% of Earth’s crust is silicon  2 nd most common element Sand  a compound of silicon & oxygen

Silicon A semi-conductor Under some circumstances silicon conducts electricity and at other times it does not Adding elements to silicon changes its conductivity Silicon is used to make electric circuits found in computer chips

NONMETALS & Nobel Gases Solid nonmetals  do not conduct electricity and dull in color They are brittle (break easy) Example is Sulfur Sulfur used in car batteries Phosphorus – the striking surface of safety matches is a nonmetal

Nonmetal gases Nitrogen – 78% of the air you breath Oxygen – most abundant element on earth: 21% of air you breath and 47% Earth’s crust Combines with many metals RUST – combination of iron & oxygen

Last column of periodic table NOBEL GASES – rarely combine with other elements to form compounds Helium – lighter than air Will glow if an electric current is passed through them – Used to make neon signs

A _____________ is made of two or more elements combined chemically. Compound

______________ are elements that rarely combine with other elements to form molecules. Nobel Gases

Elements are arranged by properties in the _______________ Periodic table

_______________ are usually shiny and bendable. Metals

An element’s ________________ is an abbreviation of its name, sometimes from Latin or Greek. Chemical symbol

In the periodic table a column is called a____________. group

What requires a chemical reaction to form? A compound

List three properties of metal. Shiny, reflect light, bendable, stretchable, able to conduct electricity and heat