CHAPTER 5The Periodic Table

Section 5.1

In 1750, only 17 elements were known. As the rate of discovery increased, so did

the need to organize the elements In 1789 Antoine Lavoisier grouped the

known elements into metals, nonmetals, gases, and earths.

Mendeleev’s Periodic Table  Medeleev made flash cards of the 63 known

elements. (1863) On each card he put the name of the element, mass, and

properties. When he lined the cards up in order of increasing mass, a

pattern emerged. Mendeleev arranged the elements into row in order of

increasing mass so that elements with similar properties were in the same column.

A deck of cards can be divided into four suits—diamonds, spades, hearts, and clubs. In one version of solitaire, a player must produce an arrangement in which each suit is ordered from ace to king. This arrangement is a model for Mendeleev's periodic table.

Periodic Table- Arrangement of elements in columns, based on a set of properties that repeat from row to row.

Mendeleev’s Prediction He could not make a complete table because many of the

elements had not yet been discovered. He had to leave spaces for those elements. Eka-Aluminum – one space below Al. He predicted it would be a

soft metal with a low m.p. and a density of 5.9 g/cm3

The close match between Mendeleev’s prediction and the actual properties of new elements showed how useful the periodic table could be. Gallium was discovered in 1875. It’s a soft metal, m.p. is 29.7 ˚C,

and has a density of 5.91 g/cm3

Heat from a person's hand can melt gallium. In some traffic signals, there are tiny light emitting diodes (LEDs) that contain a compound of gallium

http://en.wikipedia.org/wiki/File:Mendelejevs_periodiska_system_1871.png

Mendeleev’s Periodic Table

How is the table organized?Elements are arranged in order of

increasing mass. What do the long dashes represent?

They represent undiscovered elements. Why are masses listed with some of the

dashes, but not with all of them?He was able to predict properties for

some unknown elements based on the properties of neighboring elements.

5.2 The Modern Periodic Table

The sounds of musical notes that are separated by an octave are related, but they are not identical. In a similar way, elements in the same column of the periodic table are related because their properties repeat at regular intervals. But elements in different rows are not identical.

Periodic Law

Mendeleev developed his chart before the proton was discovered.

In the modern periodic table, elements are arranged by increasing atomic number. (# of protons)

Periods- Each row in the table of elements is a period. Groups- Each column on the periodic table is called a

group. Properties of elements repeat in a predictable way

when atomic numbers are used to arrange elements into groups. Members of a group have similar chemical properties.

This pattern of repeating properties is called periodic law.

Periods

Periods - the rows; represent energy levels. Row 1 (energy level 1) 2 elements Row 2 (energy level 2) 8 elements Row 3 (energy level 3) 18 elements Row 4(energy level 4) 32 elements

The number of available orbitals increases from energy level to energy level.

Elements change from metals to metalloids to nonmetals as you move from left to right across the period.

Groups

Groups/Families - the columns. Atomic masses increase from top to bottom.

Members of a group have similar electron

configurations and therefore have similar chemical properties.

Tells how many valence electrons are in the last energy level of an element.***

Valence electrons increase from left to right on the periodic table.

Valence electrons – an electron that is in the highest occupied energy level of an atom.

Valence Electrons

A valence electron is an electron that is in the highest occupied energy level of an atom.

They play a key role in chemical reactions.

The # of valence electrons increases from left to right.

Elements in a group have similar properties because they have the same number of valence electrons.

Group Valence Electrons

1A 1

2A 2

3A 3

4A 4

5A 5

6A 6

7A 78A 8

Valence Electrons

Electron configuration is the arrangement of electrons in an atom.

The most stable electron configuration is one in which the outermost electron shell is completely filled.

Atoms will gain or lose electrons in order to achieve the most stable electron configuration.

Atomic Mass Mass Number is the # protons plus the #

neutrons. Atomic mass is a value that depends on the distribution of

an element’s isotopes in nature and the masses of those isotopes.

All atoms of the same element do not have the same atomic mass.

Average atomic mass of an element is a weighted average of the masses of an elements isotopes.

The unit for atomic mass is – AMU The standard on which the atomic mass unit is based is

the mass of a Carbon-12 atom.

Average Atomic Mass

Weighted Averages – some values are more important that other values For isotopes, the one that occurs more in

nature contributes more to the average atomic mass.

Solving for Average Atomic Mass

When solving, Convert the % abundance to a decimal Multiply by its mass Add the products together EX:

Chlorine-35 75.78% 0.7578 X 34.969 = 26.4995 Chlorine-37 24.22% 0.2422 X 36.966 = +8.9532

35.4527 amuYou Try:

Isotope Mass (amu)

% abundance

27X 27.977 92.2328X 28.976 4.6729X 29.974 3.10

Classes of Elements 1. Chemical symbols are color coded by

solids, liquids, and gases. The symbols for solids are black. The symbols for

liquids are purple. The symbols for gases are red. 2. Elements are divided into those that

occur naturally and those that do not The symbols for elements that don’t occur

naturally are white 3. They are also classified by their general

properties. METALS, NONMETALS, METALLOIDS In the periodic table, metals are located on the

left, nonmetals are on the right, and metalloids are in between.

METALS majority of elements good conductors of heat and electricity most are solids at room temp. (except Hg) most are malleable and ductile –ability to

be drawn into wires some are reactive, some are not.

Ex. Gold Ex. Mg

Magnesium and aluminum are typical metals

Transition Metals

The metals in groups 3-12 are called Transition Metals.

They form a bridge between the two sides of the table. They are well known for their ability to form compounds with distinctive colors.

A compound of erbium (Er) and oxygen is used to tint glass pink.

Nonmetals properties are opposite of metals. poor conductors many are gases at room temp. the solids tend to be brittle Some are very reactive, some don’t react at

all. Ex. F is most reactive element. Ex. Ne is not

reactive.Toothpaste contains a compound that helps to protect teeth from tooth decay. The compound is formed from the nonmetal fluorine and the metal sodium

Metalloids elements with properties that fall between those

of metals and nonmetals. Ex. A metalloid’s ability to conduct electricity can vary

with temperature. Si and Ge are insulators at low temps. and conductors at high temps.

Variation Across a Period Across a period from left to right, the elements become less metallic.

From left to right across Period 3, there are three metals (Na, Mg, and Al), one metalloid (Si), and four nonmetals (P, S, Cl, and Ar). Many light bulbs are filled with argon gas.

5.3 Representative Groups

“A” groups are #1-8 The number of the group is equal to the

number of valence electrons in an atom of that element.

Valence electrons- An electron that is in the highest occupied energy level of an atom. 

Elements in a group have similar properties because they have the same number of valence electrons. (This is why H is grouped with metals)

Alkali Metals

Group 1A Most reactive metals

Reactivity increases from the top to the bottom.

So reactive many are kept under oil to prevent reacting with water or oxygen.

One Valence Electron Found in nature only in a

compound. Form +1 ions because they

will easily give up 1 electron for stability.

http://www.youtube.com/watch?v=Ft4E1eCUItI http://www.youtube.com/watch?v=eCk0lYB_8c0

Element SymbolHyperlink

Lithium Li

Sodium Na

Potassium

K

Rubidium

Rb

Cesium Cs

Francium

Fr

Alkaline Earth Metals Group 2A Have 2 Valence Electrons Harder than the metals in

1A. Form +2 Ions because

they easily give up 2 electrons for stability.

Magnesium used in photosynthesis within the chlorophyll.

Calcium used in teeth and bone.

http://www.youtube.com/watch?v=B2ZPrg9IVEo

Element SymbolHyperlink

Beryllium Be

Magnesium

Mg

Calcium Ca

Strontium Sr

Barium Ba

Radium Ra

Boron Family Group 3A Have 3 Valence electrons Form +3 Ions because

they easily give up 3 electrons for stability.

1 metalloid (Boron) Six metals Aluminum is the most

abundant metal in the Earth’s crust.

People are encouraged to recycle aluminum because it doesn’t take that much energy to do so.

Element Symbol Hyperlink

Boron B

Aluminum

Al

Gallium Ga

Indium In

Thallium Tl

Ununtrium

Uut

Carbon Family Group 4A Have 4 Valence Electrons Form +/- 4 Ions because it

will easily lose or gain 4 electrons for stability.

1 Nonmetal (Carbon) 2 Metalloids 3 Metals Metallic nature increases

from top to bottom. With the exception of water,

most of the compounds in your body contain carbon.

Silicon is the second most abundant metal in the earth’s crust.

Element SymbolHyperlink

Carbon C

Silicon Si

Germanium

Ge

Tin Sn

Lead Pb

Ununquadium

Uuq

Nitrogen Family Group 5A Have 5 Valence

Electrons Forms -3 Ions

because it will easily gain 3 electrons for stability.

2 nonmetals 2 metalloids 2 Metals Nitrogen and

Phosphorus are used in fertilizers.

Element SymbolHyperlink

Nitrogen N

Phosphorus P

Arsenic As

Antimony Sb

Bismuth Bi

Ununpentium

Uup

Oxygen Family Group 6A Have 6 Valence Electrons Forms -2 Ions because it will

easily gain 2 electrons for stability.

3 nonmetals 2 metalloids 1 metal Oxygen is the most abundant

element in the Earth’s Crust. Ozone is another from of

oxygen. At ground level it can irritate your eyes and lungs. At higher levels it absorbs harmful radiation from the sun.

Element SymbolHyperlink

Oxygen O

Sulfur S

Selenium Se

Tellurium Te

Polonium Po

Ununhexium

Uuh

Halogens Group 7A Have 7 Valence electrons Form -1 Ions because it will

easily gain 1 electron for stability.

Most reactive nonmetals increase from bottom to top.

Known as “Salt Formers” 5 nonmetals 1 Unknown Fluorine is the most reactive. React easily with most metals. http://

www.youtube.com/watch?v=u2ogMUDBaf4 http://

www.youtube.com/watch?v=yP0U5rGWqdg

Element Symbol Hyperlink

Fluorine F

Chlorine Cl

Bromine Br

Iodine I

Astatine At

Ununspetium

Uus

Noble Gases Group 8A 8 Valence Electrons Helium is the exception

with only 2 valence electrons.

Extremely Un-reactive (Do not form Ions)

Odorless and colorless. Used in light bulbs. All are used in neon lights

except argon. Have the most stable

electron configuration. http://

www.youtube.com/watch?v=QLrofyj6a2s

Element SymbolHyperlink

Helium He

Neon Ne

Argon Ar

Krypton Kr

Xenon Xe

Radon Rn

Ununoctium

Uuo

Patterns on the Periodic Table

1. Atomic # L to R. 2. Atomic mass L to R. 3. Energy level and orbitals in rows from T to B.4. (Physical Properties) metals metalloids

nonmetals from L to R.5. Columns atomic mass from T to B.6. Columns are based on chemical properties

(reactivity).7. Valence Electrons from L to R.8. Most reactive metals are on the left side.9. Most reactive non-metals are on the right side.