1 periodic table & periodic law chapter 6. 2 objectives 6.1 trace the development and identify...
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Periodic Table &
Periodic Law
Chapter 6
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Objectives 6.1
Trace the development and identify key features of the periodic table
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Development of Modern Periodic Table
Section 6.1
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History of the Periodic Table
Some elements like Au and Ag were known since prehistoric times
Wikipedia.com
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Antoine Lavoisier
French scientist, late 1790s
Compiled list of 23 elements known at that time
Tried to organize it
Wikipedia.com
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1800s
Electricity breaks down into component elements
Spectrometer identified newly isolated elements
Industrial revolution (mid-1800s) led to new chemistry related industries Petrochemicals, soaps, dyes, fertilizers Created chemical pollution
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More info
1860 Scientist agreed on method to determine
atomic masses
1870 70 known elements
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John Newlands (1837-1898)
1864 English Chemist When elements arranged by atomic mass,
properties repeated every eighth element This is periodic since it repeats in pattern
He called this the Law of Octaves Critics did not like music analogy, law didn’t
work for all known elements
Wikipedia.com
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Newland’s Table
http://mooni.fccj.org/~ethall/period/period.htm
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Lothar Meyer (1830-1895)
1869 German Chemist Made connection between atomic mass and
element properties Same time as Mendeleev
Wikipedia.com
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Dmitri Mendeleev (1834-1907)
1869 Russian chemist Connection of atomic mass to elemental
properties Gets credit b/c published first and
demonstrated its usefulness Organized first PT Arranged by atomic mass Left spaces for “unknown” elements
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Problems with Mendeleev’s PT
Some element properties did not match up when placed according to atomic mass
Wikipedia.com
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Mendeleev’s PT
http://mooni.fccj.org/~ethall/period/period.htm
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Henry Moseley
1913 English chemist who discovered # p+ =
atomic # Arranged PT according to atomic # and
“fixed” Mendeleev’s problem Periodic Law – there is a periodic repetition of
chemical & physical properties of elements when arranged by increasing atomic #
Wikipedia.com
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Moseley’s PT
http://mooni.fccj.org/~ethall/period/period.htm
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Modern PT
Groups – AKA families; columns
Periods – rows; 7 total and growing?
Representative elements – 1A through 8A
Transition elements – 1B through 8B
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Classifying elements
Metals shiny when smooth and clean solid at room temp good conductors of electricity & heat malleable and ductile
Include most of Group A and all Group B Group 1A – Alkali metals (except H) Group 2A – alkaline earth metals Both groups chemical reactive (1A > 2A)
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Classifying elements (con’t)
Group B Transition metals Inner transition metals
Lanthanides Phosphors – emit light when struck by e-
Actinides
Wikipedia.com
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Classifying elements (con’t)
Nonmetals Located right upper side Gases or brittle, dull-looking solids Poor conductors of heat and electricity Br is only nonmetal liquid at room temp
Halogens (Group 7A) Noble gases (Group 8A)
Not reactive
Wikipedia.com
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Classifying elements (con’t)
Metalloids or semi-metals Have physical and chemical prop of metals
and nonmetals
Examples (uses):
Ge (cell phones)
Si (computer chips)
Wikipedia.com
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Objectives 6.2
Explain why elements in the same group have similar properties
Identify the four blocks of the periodic table based on electron configuration
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Classification of the Elements
Section 6.2
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Organizing by e- configuration
Period 1 H 1s1 1s1
Period 2 Li 1s22s1 [He]2s1
Period 3 Na 1s22s22p63s1 [Ne]3s1
Period 4 K 1s22s22p63s23p44s1
[Ar]4s1
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Valence e-
Atoms in the same group have similar chemical properties because they have the same number of valence e-
Group 1A all have 1 e- in last energy level
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Valence e- and periods
Energy level of element’s valence e- = the period #
Ex: lithium’s valence e- is in the second energy level Lithium is in the second period
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Valence e- and group #
The group # = the valence e- # Applies to representative elements ONLY
Ex: Group 5A has 5 e-
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S-block
Group 1A has e- configuration of s1
Group 2A has e-configuration of s2
S orbital is full with 2 e-
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P-block
Group 3A to 8A Holds max of 6 e- S- and p- blocks comprise all of the
representative elements Noble gases
group 8A Nearly no chemical rxn Stable!
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D-block
Contains transition metals Largest block Spans 10 groups S filled and partially filled d
Ex: Scandium [Ar]4s23d1
Titanium [Ar]4s23d2
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F-block
Contains inner transition metals
Filled/partially filled s, 4f and 5f
Spans 14 columns
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Objectives 6.3
Compare period and group trends of several properties
Relate period and group trends in atomic radii to electron configuration
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Periodic Trends
Section 6.3
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Atomic radius
Atomic size How close an atom lies to another atom
Atomic radius Half the distance between adjacent nuclei
http://www.chemguide.co.uk/atoms/properties/atradius.html
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Atomic Radius Trends
http://intro.chem.okstate.edu/1314F00/Lecture/Chapter7/Lec111300.html
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Why does the atomic radius decrease within a period? Increase # p+ and e- Each e- is added to the same energy level Nuclear charge becomes more + as we move
from left to right Valence e- are not shielded from increased
nuclear charge What happens?
Outermost e- pull closer to nucleus
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Why does the atomic radius increase within a group? Add energy levels or orbital Make atom larger Outer e- are farther away Valence e- shielded by added distance and
not affected by nuclear charge
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Which has the largest atomic radius?
C, F, Be, or Li
1. Find the location of the elements. All P2
2. Arrange them
Li, Be, C, F
1. Find your answer Li
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Ionic radius
Atoms can gain or lose e- to form ions When atoms lose e- and form + ions, they get
smaller. The e- lost is a valence e- If the orbital is empty, the atom is smaller If the atom is smaller, the + of the nucleus will
pull the remaining e- towards it
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Ionic radius (con’t)
When atoms gain e- and form (–) ions, they become larger.
Adding e- to outer shell increases electrostatic repulsion between existing e- to move them farther apart.
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What does the ionic radius do within a period? Decreases as you move across the period
Refer to page 166 in text
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What does the ionic radius do within a group? Increases as you move down the group
Refer to page 166 in text
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Ionization energy
Energy required to remove an e- from a gaseous atom
The energy needed to remove the first e- is called first ionization energy
The amount of energy needed to remove the second e- from a 1+ ion is called the second ionization energy, etc.
The more e- you try to remove, the more energy it takes, and the less likely to occur
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What does the ionization energy do within a period? Increases as you move across the period
Removing the last e- makes the nucleus “hold” the remaining e- tighter
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What does the ionization energy do within a group? Decreases as you move down the group
Because valence e- are farther from the nucleus, the hold on it is less and takes less energy
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OCTET RULE
Atoms share, gain, or lose e- to acquire a full set of 8 valence e- (except: period 1 elements)
Elements on right side of table gain e-; form (--) ions
Elements on left side of table lose e-; form + ions
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Electronegativity
The ability for an atom to attract e- to form a bond
Units: Paulings (named after American scientist Linus Pauling)
F is most electroneg Cs, Fr least electroneg
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What does the electronegativity do within a period? Increases as you move across a period
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What does the electronegativity do within a group? Decreases as you move down a group
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Summary of Trends
Atomic radius
-Size of atom
Decrease
Left to right
Increase
Top to bottom
Ionic radius
-Size of ion
Decrease
Left to right
Increase
Top to bottom
Ionization energy
-Energy to lose e-
Increase
Left to right
Decrease
Top to bottom
Electronegativity
-Ability to attract e-
Increase
Left to right
Decrease
Top to bottom
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Credits
Clip art from Microsoft Clip art and Wikipedia as well as other sources documented throughout the presentation
Information obtained mainly from Glencoe Chemistry Matters textbook, Texas ed.
Arranged and explained by Michelle Estrada