# Chapter 5: The Periodic Table

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Chapter 5: The Periodic Table
5-1 Development of the Periodic Table 5-2 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

What do you organize? 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

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 known elements

Forerunners of the Periodic Table
J.W. Dobereiner ( ) 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 = ( )/2 = 81.2

Forerunners of the Periodic Table
J.A.R. Newlands ( ) 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 ( ) and Lothar Meyer ( ) In 1869, published nearly identical classification methods Mendeleev’s is more well known Classified elements by their atomic masses

The Periodic Law 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

Section Review 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?

Explain why elements in a group have similar properties Identify the four blocks of the periodic table

Organizing the Squares
Groups: columns Periods: rows

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

Metals, Nonmetals, and Metalloids
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
Upper right hand corner of table Usually gases Neon Bromine

Metals, Nonmetals, and Metalloids
Have a combo of metal and nonmetal properties Elements that touch the stair step line Exceptions: boron and aluminum

Practice Problems 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

activity

Electron Configuration and the Periodic Table
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? How many valence electrons does Ca have?

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

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

S block

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

p-blocks s-blocks

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

p-blocks s-blocks d-blocks

The s-, p-, d-, and f-block Elements
Inner transition metals f orbitals can hold up to 14 electrons so there are 14 groups/columns

p-blocks s-blocks d-blocks f-blocks

5-3 Periodic Trends Define 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 d 2

Atomic Radius Trends in periods Trends in groups
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