Chapter 5: The Periodic Table
description
Transcript of Chapter 5: The Periodic Table
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