Unit 4- The Periodic Table• Alkali metals• Alkaline-earth metals• Alloy• Atomic radius• Bond radius• Electron shielding• Electronegativity• Family• Group • Halogen• Ionic radius

• Ionization energy• Main-group elements• Metal• Metalloid• Noble/inert gas• Nonmetal• Period• Periodic law• Transition metal• Valence electron

The elements of Earth’s crust

Cross Classification

Grouping by SeveralCharacteristics

at Once

A Small ProblemSU

ITS

NUMBERS

• You have 51 cards in a deck.

• Grouping the cards by suit and by number reveals the missing card.

What is the fastest way to find out which card is missing?

• Classification – grouping based on similarities (just like we did with the playing cards)

• Consider a supermarket:o All the dairy foods are in one

section.o All the produce is in another

section.• Grouping helps the shoppers to

find what they are looking for.

The Value of Classification

• Lets take a closer look at the dairy section.

• There are additional classifications withinthe dairy section.

• Soy products can be in the produce section too! Soy fits in two classifications at once!!

Refining Classification

Whole milk

Skim milk

Soy milk

Lactaid

• Cross Classification - classifying into more than one group at a time

• Exampleso Deck of cards

Suits and Numberso Periodic Table

Groups or Families and Periods

Cross Classification

• What do the elements in a vertical column of the Periodic Table have in common?They have the same number of valence electrons.

Cross Classification on the Periodic Table

• What do the elements in a horizontal row of the Periodic Table have in common?They have the same number of shells.

Cross Classification on the Periodic Table

• Vertical columnso Called groups or families.o Have elements with similar arrangements of valence

electrons.o Valence electron- electrons in the outermost shell of

an atom; determines atom’s chemical properties• Horizontal rows

o Called periods.o Have elements with the same number of shells.

SummaryClassification on the Periodic Table

Development of thePeriodic Table

MendeleevVs

Moseley

• Dmitri Mendeleev (1869) prepared a card for each of the known elements. He listedo the symbol,o the atomic mass,o and the chemical properties.

Mendeleev

• Mendeleev arranged the cards in order of increasing atomic mass.

• He noticed a pattern.

• The properties repeated regularly.

More Mendeleev

• Mendeleev moved the cards, keeping them in order of mass, so the first one with repeating properties was under the one similar to it.

• The cards thus arranged formed groups or families with similar properties.

• This arrangement forms the basis for the first Periodic Table.

Even More Mendeleev

• Based on his observations, Mendeleev concluded:

• This is known as the Periodic Law.

Mendeleev’s Periodic Law

When the elements are arranged in increasing order of atomic mass, the chemical

properties repeat periodically.

• Look through the Periodic Table. Are all the elements in order with respect to mass?

• Which elements are out of order with respect to mass?

• Mendeleev was aware of some of these discrepancies.o He knew that if tellurium and iodine were

in the right family, they were out of order with respect to mass.

o He believed that when scientists improved techniques for measuring atomic mass, these discrepancies would disappear.

Could Mendeleev be Wrong?

Ar–K; Co–Ni; Te–I; Th–Pa; U–Np; Pu–Am

No

He was wrong!!

• Mendeleev found an important pattern − repetition of properties. But does it make sense to think that the pattern is caused by mass?

• What parts of an atom affect its mass?

• What parts of an atom affect its properties?

• Today we know that different isotopes of the same element have the same properties, but have different masses because of neutrons which affect the mass, but not the properties.

• Mendeleev does not make sense. Mass does not cause chemical properties.

Did Mendeleev Make Sense?

protons and neutrons

protons and electrons

• When the elements were ordered so each was in the correct family some were out of order with respect to mass.

• When the elements are placed in the proper order, they are numbered sequentially. This number is called the atomic number.

• By using a technique called X-ray diffraction, Henry Moseley (1913) showed that the atomic number was the nuclear charge or the number of protons.

Moseley

• Moseley showed that when the elements are arranged in order of atomic number (as measured by X-ray diffraction), the discrepancies in Mendeleev’s Periodic Table disappear.

• Moseley corrected the Periodic Law:

• This is the basis for the modern Periodic Table.

The Real Periodic Law

When the elements are arranged in increasing order of atomic number, the chemical

properties repeat periodically.

• When Mendeleevarranged the elementsin order of increasingmass, he inadvertentlyarranged them in orderof atomic number, withfew exceptions.

• The graph to the rightshows that there is adirect relationshipbetween atomic massand atomic number.

How did Mendeleev Succeed (even though he was wrong)?

• Each element has its own box on the Periodic Table with a lot of information in it.

• There is a key to tell you what information in each box means.Although Periodic Tables differ, most have the same basic information.

• Starting from the top of the box, the information on the key to theright is as follows: o [1] atomic mass - weighted average of the mass of the common isotopes of

the element; o [2] common oxidation states - tells number of electrons lost, gained or shared

during bonding; o [3] symbol - one, two, or three letters related to the name with the first letter

capitalized and other letters lower case. The three letter symbols are systematic names that represent the atomic numbers of unnamed elements;

o [4] atomic number - number of protons; and o [5] electron configuration - arrangement of electrons in energy levels

What Information is on the Periodic Table?

WRITEDOWN

A Quick Tour of The Periodic Table

Why is the Periodic Table important to me?

• The periodic table is the most useful tool to a chemist.

• You get to use it on every test.

• It organizes lots of information about all the known elements.

Groups…Here’s Where the Periodic Table Gets Useful!!

• Elements in the same group have similar chemical and physical properties!!

• (Mendeleev did that on purpose.)

Why??• They have the same

number of valence electrons.

• They will form the same kinds of ions.

Families on the Periodic Table

• Columns are also grouped into families.

• Families may be one column, or several columns put together.

• Families have names rather than numbers. (Just like your family has a common last name.)

Hydrogen- it’s own group

• Hydrogen belongs to a family of its own.

• Hydrogen is a diatomic, reactive gas.

• Hydrogen was involved in the explosion of the Hindenberg.

• Hydrogen is promising as an alternative fuel source for automobiles

Group 1- Alkali Metals

• 1st column on the periodic table NOT including hydrogen

• Very reactive metals, always combined with something else in nature (like in salt).

• Soft enough to cut with a butter knife

Group 2- Alkaline Earth Metals• Second column on the

periodic table• Reactive metals that are

always combined in nature

• Several of these elements are important mineral nutrients (such as Mg and Ca

Transition Metals

• Elements in groups 3-12• Less reactive harder

metals• Includes metals used in

jewelry and construction.

• Metals used “as metal.”• Used to color paints

Group 13- Boron Family

• 3 valence electrons• Aluminum metal was

once rare and expensive, not a “disposable metal”

• B is a metalloid all the rest are metals

Group 14- Carbon Family• 4 valence electrons• Nonmetals, metalloids

and metals• Contains elements

important to life and computers.

• Silicon and Germanium are important semiconductors

Group 15- Nitrogen Family• 5 valence electrons, tend

to share when they are bonded

• Nonmetals, metalloids and metals

• Nitrogen makes up over ¾ of the atmosphere.

• Nitrogen and phosphorus are both important in living things.

• Most of the world’s nitrogen is not available to living things.

• The red stuff on the tip of matches is phosphorus.

Group 16- Oxygen Family• 6 valence electrons• Oxygen is necessary

for respiration, most abundant element of Earth’s crust, reactive and combines with many other elements

• Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)

Group 17- Halogens

• 7 valence electrons• Very reactive, volatile,

diatomic, nonmetals• Always found

combined with other element in nature

• Used as disinfectants and to strengthen teeth.

Group 18- The Noble Gases

The Noble Gases

• Have a full valence shell so…

• VERY unreactive, monatomic gases

• Used in lighted “neon” signs

• Used in blimps to fix the Hindenberg problem.

Periodic Table: Metallic arrangement• Layout of the Periodic Table: Metals vs. nonmetals

1IA

18VIIIA

12IIA

13IIIA

14IVA

15VA

16VIA

17VIIA

2

33IIIB

4IVB

5VB

6VIB

7VIIB

8 9VIIIB

10 11IB

12IIB

4

5

6

7

MetalsNonmetals

Periodic Table: The three broad ClassesMain, Transition, Rare Earth

• Main (Representative), Transition metals, lanthanides and actinides (rare earth)

Reading the Periodic Table: Classification• Nonmetals, Metals, Metalloids, Noble gases

Properties of Metals

• Conduct electricity and heat• Lose valence electrons easily• Malleable- can be pounded into

thin sheet• Ductile- can be pulled into wire• Low electronegativity• Solid at room temp. (except Hg)• Different metals can be mixed to

form an alloy

Properties of Nonmetals

• Poor conductor of heat and electricity• Brittle- if solid• Gain or share valence electrons easily• Nonductile• Solid, liquid or gas at room temp.• High electronegativity

Sulfur

Properties of Metalloids or semi-metals

• Solids that can be dull or shiny• Have characteristics of both

metals and nonmetals• Ductile and malleable• Conduct heat and electricity

better than nonmetals but not as good as metals

• Useful in computer chip material

18

1 2 13 14 15 16 17

2

3

4

5

6

7

Resulting Arrangement

METALS

NONMETALS

NOBLE

GASES

1 2

3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18

19 20

1 2

2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8

2-8-1 2-8-2 2-8-3 2-8-4 2-8-5 2-8-6 2-8-7 2-8-8

2-8-8-1 2-8-8-2

B C Si Ge As Sb Te

Trends in the Periodic TableInterpreting the Periodic Table

Going across the table from left to right within a row or period

• The number of protons increases.• The pull on the electrons increases.• Metallic properties decrease (except in the transition elements)

o Ionization energy increases.• Ionization energy - energy needed to remove the most loosely held electron from

an element in the gaseous phase• Found in Table S

o Electronegativity increases (also Table S).o There is a gradual change from positive oxidation states to negative

oxidation states.• The number of valence electrons increases.• The number of shells remains the same.

Going down the table within a group or family

• The number of protons increases.• The number of shells increases.• The atomic radius increases.– Gets smaller across table due to more pull from

electrons on an increasingly positive nucleus• The pull on the electrons decreases.• Metallic properties increase.• The number of valence electrons remains the

same.

Trend in Atomic Radius•Atomic Radius:

•The size of at atomic specie as determine by the boundaries of the valence e-. Largest atomic species are those found in the SW corner since these atoms have the largest n, but the smallest Zeff.

Ionic Radius:-radius of ions- Follows the same trends as

atomic radius

Trend in ElectronegativityElectronegativity:Discovered by Linus Pauling

- A scale of numerical values that reflect how much an atom in a molecule attracts electrons

Trend in Ionization EnergyIonization potential: The energy required to remove the valence electron from an atomic specie. Largest toward NE corner of PT since these atoms hold on to their valence e- the tightest.

Trend in Electron AffinityElectron Affinity:

The energy change that occurs when a neutral atom gains an electron. Most favorable toward NE corner of PT since these atoms have a great affinity for e-.

Summary of Trend• Periodic Table and Periodic Trends• 1. Electron Configuration

2. Atomic Radius: Largest toward SW corner of PT

3. Ionization Energy: Largest toward NE of PT4. Electron Affinity: Most favorable NE of PT

Summary• Periodic Table: Map of the Building block of matter• Type: Metal, metalloid and Nonmetal• Groupings: Representative or main, transition and

Lanthanide/Actanides

• Family: Elements in the same column have similar chemical property because of similar valence electrons

• Alkali, Alkaline, halogens, noble gases

• Period: Elements in the same row have valence electrons in the same shell.

• Table S--- a lot of information regarding each element!!