Chapter 5: The Periodic Table

5-1 Development of the Periodic Table5-2 Reading the Periodic Table

5-3 Periodic Trends

5-1Developement of the Periodic Table

State the periodic law

Discuss contributions that Dobereiner, Newlands, Mendeleev, and Mosely made to the periodic table

The development of the periodic table was one of the biggest achievements of chemistry

It brought order to thousands of ideas and what seemed like unrelated facts

It helped chemists predict the existence of elements that hadn’t been discovered yet

What do you organize?

Forerunners of the Periodic Table 1790’s - only knew of 23 elements 1800’s - Introduction of electricity helped

break compounds down into elements scientists didn’t know existed.

mid-1800’s Industrial Revolution – new chemistry related industries

1870 - 70 known elements

J.W. Dobereiner (1780-1849)◦ In early 1800’s classified elements into groups of

three◦ Could see a pattern of similar traits◦ Called the sets, triads

Example: lithium, sodium, potassium calcium, strontium, barium chlorine, bromine, iodine

◦ Placed them in this order b/c the middle element has a mass equal to the average masses of the other 2 atomic mass of Br = 79.9 avg atomic mass of Cl and I = (35.5+126.9)/2 = 81.2

Forerunners of the Periodic Table

J.A.R. Newlands (1837-1898)◦ In 1865, first to see a pattern

Realized the elements’ properties were repeating after every 8th element

◦ Called the pattern the law of octaves after the music scale

◦ Pointed out the was a repetition or “periodic” trend to the properties

Forerunners of the Periodic Table

Dmitri Mendeleev (1834-1907) and Lothar Meyer (1830-1895)◦ In 1869, published

nearly identical classification methods

◦ Mendeleev’s is more well known

◦ Classified elements by their atomic masses

Forerunners of the Periodic Table

Henry Moseley (1887-1915)◦ Student working in

Rutherford’s lab◦ In 1913, reorganized

the periodic table according to atomic numbers

The Periodic Law

States:◦ When elements are arranged in order of

increasing atomic number, their physical and chemical properties show a periodic pattern

The Periodic Law

Restate the Periodic Law in your own words How were Dobereiner and Newlands’ ideas

helpful in creating the periodic table? What did Moseley’s work contribute to the

development of the periodic table? Which property did Mendeleev arrange his

periodic table?

Section Review

5-2 Reading the Periodic Table

Explain why elements in a group have similar properties

Identify the four blocks of the periodic table

Organizing the Squares Groups: columns Periods: rows

Alkali metals: group 1 Alkaline earth metals: group 2 Halogens: group 7 Noble gases: group 8 Transition metals: groups in the middle

Labeling and Naming Groups

Metals: most of the elements on the table◦ Great conductors of electricity◦ Malleable (able to hammer into thin sheets)◦ Ductile (able to be made into wires)◦ Very shiny

Metals, Nonmetals, and Metalloids

Nonmetals◦ Upper right hand corner of table◦ Usually gases

Metals, Nonmetals, and Metalloids

NeonBromine

Metals, Nonmetals, and Metalloids Metalloids

◦ Have a combo of metal and nonmetal properties

◦ Elements that touch the stair step line Exceptions: boron and

aluminum

For the following elements find:◦ the element symbol◦ atomic number◦ classify it as a metal, nonmetal, or metalloid◦ name the group it is in if it has one

Iodine Magnesium Gold Lithium Argon Chlorine Barium Cesium Strontium Silicon Xenon

Practice Problems

Label your periodic table

activity

Take a look:◦ Period 1 hydrogen 1s1

◦ Period 2 lithium 1s22s1

◦ Period 3 sodium 1s22s22p63s1

◦ Period 4 potassium 1s22s22p63s23p64s1

What do they have in common?◦ A single electron in their outside orbital

Electron Configuration and the Periodic Table

Valence electrons: electrons in the highest principle energy level

How many valence electrons does Be have?◦ 2

How many valence electrons does Mg have?◦ 2

How many valence electrons does Ca have?◦ 2

Electron Configuration and the Periodic Table

Atoms in the same group have similar chem properties because they have the same # of valence electrons◦ Elements in group 1A have one valence e-◦ Elements in group 2A have two valence e-◦ Elements in group 8A have eight valence e-

Electron Configuration and the Periodic Table

The period number and the principle energy level number are equal to each other◦ Li: period 2 and its e- config

1s22s1

◦ Ga: period 4 and e- config. 1s22s22p63s23p64s23d104p1

◦ What is the e- config. for the group 1A element in the 6th period? 1s22s22p63s23p64s23d104p65s24d105p66s1

Electron Configuration and the Periodic Table

s-block elements◦ Groups 1A and 2A plus hydrogen and helium

Group 1A: have one valence electron and the electron config. ends in s1

Group 2A: have two valence electrons and the electron config. ends in s2

Because only 2 e- fit in the s orbitals, there are only two “s” groups

The s-, p-, d-, and f-block Elements

S block

p-block elements◦ Filled after the s sublevel◦ Groups 3A – 8A◦ Group 8A elements are incredibly stable b/c both

the s and p orbitals are filled

The s-, p-, d-, and f-block Elements

s-blocksp-blocks

d-block elements◦ Contains transition elements◦ d orbitals can fit up to 10 electrons so there are a

total of 10 groups Group B elements

The s-, p-, d-, and f-block Elements

s-blocks d-blocksp-blocks

f-block elements◦ Inner transition metals◦ f orbitals can hold up to 14 electrons so there are

14 groups/columns

The s-, p-, d-, and f-block Elements

s-blocks d-blocksp-blocks

f-blocks

5-3 Periodic TrendsDefine the term periodic trend

Identify 4 important periodic trends and explain how each reflects the electron configurations of the elements

Atomic Radius Half the distance b/w the nucleus of one

atom and the nucleus of the closest atom next to it

d2

Atomic Radius Trends in periods

◦ Decreases as you go right Trends in groups

◦ Increases as you go down

Ionic Size Atoms can gain and lose electrons When they do, they form ions

◦ When they lose e-, they grow smaller◦ When they gain e-, they grow larger

Trends within periods◦ Decrease as you move right until Nitrogen

Trends within groups◦ Increase as you move down

Ionization Energy Energy needed to remove an electron from

an element/atom The more electrons you remove, the more

energy is needed Trends within periods

◦ Increase as you move right Trends within groups

◦ Decrease as you move down

Practice Problems Boron, carbon, and aluminum occur near each

other in the periodic table, which is the largest? Which has the highest ionization nrg?◦ Al is largest and C has highest ionization nrg

Which of the following atoms is smallest: lithium, beryllium, or magnesium? Which has the highest ionization nrg?◦ Be is smallest and has highest ionization nrg

Which of the following is the largest: a sodium atom, a sodium atom with a +1, or a potassium atom?◦ K atom

Octet rule Atoms tend to gain, lose, or share electrons

in order to get a full set of eight electrons Atoms will do anything to get these eight

Electronegativity The relative ability of atoms to attract

electrons to themselves Trends within periods

◦ Increases as you move right Trends within groups

◦ Decreases as you move down