Unit 4: Periodic Law Chief of Springfield Periodic Police
Department Clancy Wiggum
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Castagno Chemistry Challenge IV Rules: 1) You are working as a
CLASS ! 2) You will have 5minutes! 3) There are 11 questions so the
highest score gets the points. POINTS Class:1 st 2pts, 2 nd 1pt, 3
rd 0pts, 4 th 0pts Questions?
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Castagno Chemistry Challenge IV Sections of the periodic table
are known by certain names On the blank table you are provided,
match the section name to the area (lettered A, B, C, etc.). The
list is on the next slide. You will have 5mins Questions?
Castagno Chemistry Challenge IV Answers are on next slide
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AAAAAAAAAAAA BBBBBBBBBBBB C C DDDDDDDD D D E E E E HHHHHHHHHHHH
GGGGGGGG F F F F K IIIIIIII JJJJJJJJ Castagno Chemistry Challenge
IV Unit 4 Periodic Law Answers: A Alkali Metals E Metalloids I Rare
Earths B Alkaline Earth F Ungrouped NMs J Actinides C Transition
Metals G Halogens K Disputed D Ungrouped Metals H Noble Gases
Name:
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Unit 4 Objectives Key terms (Periodic Law, groups, families,
rows, columns, atomic radii, ionic radii, ionization energy,
electron affinity, electron negativity) How the modern periodic
table was developed and arranged. The properties of vertical
columns and horizontal rows on the periodic table. The trends in
atomic radii, ionic radii, charge, metallic character, ionization
energy, electron negativity and electron affinity. Periodic means
to show a pattern. The periodic table can be used as a predicative
device. For a given element, its properties can be determined by
its position on the periodic table. The number of periods on the
periodic table is due to the number existing energy levels The
number of groups on the periodic table is due to the way orbitals
are filled by electrons. Elements with similar properties have
similar outer energy level electron configurations.
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Essential Questions Why is the Periodic Table arranged the way
it is? How can the Periodic Table be used to make predictions of
elemental properties? GUIDING QUESTIONS: What are the developments
that led to the modern periodic table? How do vertical columns and
horizontal rows on the periodic table compare? What causes Periodic
variation of the properties of the elements? What are the trends in
atomic radii, ionic radii, charge, metallic character, ionization
energy and electron affinity?
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Your Take Why are some element symbols not filled in? (P2)
Where is element 113 and others? Why do they have 3 letters? Why is
the f block under the periodic table? Why is there a gap between s
and p? Why are atomic masses found in brackets after 84? What is an
ionic charge? (P4) Why is helium floating? Why are some symbols in
different colors? How long do elements last? (P6) New v Former
designation? How long did it take to make? (P7) Are they adding new
elements? Updating? Undiscovered elements? How do they study
radioactive elements?
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History I* The first recorded discovery of an element was by
Hennig Brand. In an attempt to create the Philosophers Stone, he
distilled human urine and eventually was left with a white
substance that glowed phosphorus. The first list of non-classical
(earth, air, water, fire) elements was by Antoine Lavoisier in
1789. 33 elements but the list included light and caloric, as well
as hydrochloric acid Caloric is what scientists believed heat was
composed of
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History II* In 1817, chemist Johann Wolfgang Dobereiner found
triads or groups of 3 elements with similar properties (behavior)
Cl, Br, I / Ca, Sr, Ba / S, Se, Te / Li, Na, K John Newlands,
working with 56 elements (23 more than Lavoisier) discovered that
organizing the elements by weight resulted in a repeating pattern
of properties every 8 elements Law of Octaves
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History III* In 1860, more than 60 elements had been
discovered. Different chemists used different values (ie: atomic
mass) for the same element. This means every table is going to be
different. Cannizzaro, later in the year, presented a widely
accepted method to determine the atomic mass. Chemists were finally
closing in on the right organization.
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Mendeleev I Wrote down every known element and its properties
on cards. He rearranged them according properties such as
reactivity and mass looking for patterns.
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Mendeleev Reenactment We can easily recreate what Mendeleev
did. So we shall!
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Mendeleevs Table
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Mendeleev II When arranged according to atomic mass, elements
with similar properties appeared at regular intervals. A repeating
pattern is known as periodic.
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Mendeleev IIA But does this actually work? Take a look at the
periodic table. Are the elements currently arranged by mass?
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Atomic Mass A quick glance at the periodic table shows mass
increases most of the time. But why not all of the time?
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Atomic Mass II The mass of an element is determined by a
weighted average of the isotopes an element has. The most abundant
isotopes skews the average towards its weight. *Hydrogen 1 is the
most abundant hydrogen isotope which is why the atomic mass of
hydrogen is almost exactly 1
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Atomic Mass Unit* The mass of the proton, neutron, and electron
are so SMALL that using them as-is is unnecessarily complex.
Therefore, the three masses were converted into atomic mass units
to make calculations easier
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Atomic Mass Unit II* Proton mass: 1.672 x 10 -27 kg Proton
a.m.u.: 1.007 Neutron mass: 1.674 x 10 -27 kg Neutron a.m.u.: 1.008
Electron mass: 9.109 x 10 -31 kg Electron a.m.u.: 0.000548
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Average Atomic Mass I* In order to calculate the mass of an
element that is seen on the periodic table, we utilize the mass of
every isotope in a.m.u. We also need the relative percent abundance
of each isotope.
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Average Atomic Mass II There are numerous isotopes of carbon
but C-12 and C-13 are the most abundant. Isotope% AbundanceMass
(amu) Carbon 110.0011.0114 Carbon 1298.912.0000 Carbon
131.1013.0033 Carbon 140.0014.0032
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Average Atomic Mass III This means our weighted average
calculation can ignore C-11 and C- 14. A normal average of C-12 and
C-13 would be (12.0000 + 13.0033) / 2 = 12.50165 According to the
periodic table, the mass of carbon is 12.011
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Average Atomic Mass IV Our average calculation must take into
account PERCENT abundance. 12.0000 * 98.9% = 11.868 13.0033 * 1.1%
= 0.143 Now we add the answers together 11.868 + 0.143 =
12.011
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Average Atomic Mass V The mass on the periodic table refers to
6.02 x 10 23 atoms. Also known as 1 mole. So atomic mass = molar
mass of an element Quantities other than 1 mole can be solved
proportionally. 2 moles = 2x molar mass 0.33 moles = 0.33x molar
mass
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Mendeleev III Published his first table in 1869. Iodine Mass is
less than tellerium. Because it behaved like F, Cl, and Br, he
placed it with those elements instead. He predicted the existence
of 3 elements in 1871. By 1886, all 3 (Sc, Ga, and Ge) were
discovered with properties similar to those he predicted.
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A Summary of Mendeleev* Unknown to Mendeleev, Lothar Meyer
published his own periodic table. Despite the obvious lack of the
Noble Gases (they had not been discovered yet), Mendeleevs table is
a good predictor of to-be-discovered elements properties. Mendeleev
initially resisted the placement of Noble Gases into the table. It
was possible to add those elements without disturbing the trends of
all the others. This is why Mendeleev gets the credit his periodic
table was a predictive tool.
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Nonetheless* The Iodine-Tellurium problem showed that arranging
the elements by mass is not good enough. Scientists searched for a
better way to arrange the elements without having to pick and
choose what elements go where. In other words, there should be
characteristic about an atom (element) that takes the choice of
placement out of the scientists hands.
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Henry Moseley Moseley worked with Ernest Rutherford analyzing
the nucleus of atoms. He found the patterns of chemical properties
fit better when elements were arranged by the number of protons in
the nucleus.
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Periodic Law Moseleys work confirmed that tellerium (an atom
with 52 protons) should be placed before iodine (53 protons).
Mendeleevs principle of periodicity was rewritten into what is now
known as periodic law The physical and chemical properties of the
elements are periodic functions of their atomic numbers.
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The Modern Table In the nearly 150 years since Mendeleev,
chemists have discovered (or created) over 50 new elements. These
new elements were inserted into the periodic table based off of the
atomic number (number of protons in the nucleus). As Mendeleev
predicted, the new elements fit neatly according to Periodic
Law.
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The Noble Gases The Noble Gases were a significant find. Helium
was discovered first (1868), but not found on earth until 1895.
Argon was found by Lord Rayleigh and Sir William Ramsay in 1894. To
fit this new class of elements onto the periodic table, Ramsay
proposed a new group. Ramsay also discovered Krypton and Xenon,
though did not discover Radon.
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The Lanthanides and Actinides Lanthanides The top row of the f
block. The elements are very similar in physical and chemical
properties they were difficult to separate and identify. Actinides
The bottom row of the f block. Composed of all radioactive
elements, most of which are manmade. The reason they are cut and
pasted below the other elements is to save space.
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Periods and Blocks
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Hydrogen and Helium Hydrogen does not fit with any specific
group. It is placed over Group 1 because it has 1 outer electron.
It does not fit in terms of reactivity or other properties. Helium
All Noble Gases have 8 outer electrons, Helium has 2. It is placed
over Group 18 (8) because of its chemical stability.
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The s Block Consists of two groups All are metals Group 1
Alkali Metals Most reactive metals known Not found isolated in
nature Can be cut with a kitchen knife Group 2 Alkaline-Earth
Metals Less reactive than alkalis Harder, denser, and stronger than
alkalis Also not found isolated in nature
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The d Block This is the largest block, right in the middle of
the table. Transition Metals Typical metallic properties Good
conductors of heat Good conductors of electricity Typically less
reactive than alkali and alkaline-earth metals Some are extremely
nonreactive (Pd, Pt, Au)
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The p Block
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The p Block II No specific group names for B, C, N, and O
groups. Halogens (Group 17 (7)) Most reactive nonmetals Form
compounds known as salts. Noble Gases (Group 18 (8)) Least reactive
elements All have full outer shells of electrons Metalloids Not a
group, but these are elements with intermediate conductive
properties.
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The f Block Lanthanides (Top row) Shiny metals Similar
reactivity to alkaline-earth metals Actinides (Bottom row) All
radioactive Th, Pa, U, and Np have all been found naturally on
earth.
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Synthetic Elements* Every element up to Californium exists
naturally on earth. Tc, Pm, Np, Pu, Am, Cm, Bk, and Cf are produced
in significant quantities by laboratories but natural nuclear
reactions produce these elements in minute quantities in earths
crust. Every element from Einsteinium and on are purely
synthetic.
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Where am I? Challenge #2 There will be clues on the following
slides and you must pick what area of the periodic table they are
found in. The areas are located on pieces of paper throughout the
classroom so just stand by your location.
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Where am I? Locations Alkali Metals Alkaline Earth Metals
Transition Metals Other (nongrouped) Metals Lanthanides Actinides
Nonmetals (nongrouped) Halogens Noble Gases Metalloids While there
is a guarantee everything WILL BE USED ONCE, there is no guarantee
on the maximum.
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Where am I #1? I am a metal often used in magnets. Despite the
fact Im not rare at all I am considered to be rare earth.
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Where am I #2?
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Where am I #3? The first element discovered that has an organic
origin. In other words, I was discovered in human urine.
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Where am I #4?
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Where am I #5? My reactions with water are legendary. I contain
elements necessary for batteries and life. Extremely soft for being
solid and float on water.
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Where am I #6?
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Where am I #7? I do not like to be bothered. My appetite for
electrons is nonexistent because I am always full.
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Where am I #8?
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Where am I #9? I conduct electricity but am not used for this
purpose. I can be molded into pipes but am no longer used for this
purpose. If I have a stomach ache, you will use me to feel
better.
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Where am I #10?
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Where am I #11? My similarly named cousin lost his status but
Ive had mine for around 70 years now. You can buy me in a store,
bringing radiation into your home to protect against fires.
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Where am I #12?
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Where am I #13? Titans and wolfs and the country of Argentina
(plus ALL of Scandinavia) all belong to me.
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Where am I #14?
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Where am I #15? My neighbors love to party and set off
fireworks when they drink water. I just prefer to relax and let it
bubble around me.
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Where am I #16?
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Where am I #17? I know that I am definitely not what I am not
but I am also definitely sure I am not quite sure what I am.
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Where am I #18?
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Where am I #19? There is one of every type of element in my
group. I am the only one like it.
Mini Review What names are used for the following groups? 1)
Group 17 Halogens 2) Group 2 Alkaline-earth metals 3) Group 18
Noble Gases 4) Group 1 Alkali Metals 5) Groups 3 12 Transition
Metals
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Mini Review II Arrange the metals in terms of reactivity from
highest the lowest: Transition, Alkali, Alkaline, Lanthanide
Alkali, Alkaline/Lanthanide, Transition For the following element,
identify the block, period, group #, group name (if applicable),
element name, element type (ie: metalloid), and reactivity (high or
low) [He]2s 2 2p 5 p-block, 2 nd period, Group 17, Halogens,
fluorine, nonmetal, high reactivity [Ar]4s 2 3d 10 d-block, 4 th
period, Group 12, transition, zinc, metal, low
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Periodic Properties Thanks to Moseley and Mendeleev, the
elements are arranged in such a way that their properties appear in
known intervals. Interestingly enough, these properties exhibit
trends across a period (row) or down a group (column).
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Property 1: Valence Electrons When chemicals react, only
electrons are lost, gained, or shared. For any element, there are
specific electrons that will interact: valence electrons. Main
Group Trend s and p block Group 1 1 valence electron (xs 1 ) Group
2 2 valence electrons (xs 2 ) Group 1 3 3 valence electrons (xs 2
xp 1 ) Group 1 8 8 valence electrons (xs 2 xp 6 ) a full octet
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Properties 2 - 6 2) Atomic Radius 3) Ionization Energy 4)
Electron Affinity 5) Ionic Radii 6) Electronegativity Get into your
lab groups and choose a property.
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Property 2: Atomic Radius one-half the distance between the
nuclei of identical atoms bonded together
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Atomic Radius - Trends Group Trend Main groups General INCREASE
in atomic radius down a group Period Trend Main groups General
DECREASE in atomic radius across a group Why? The positive charge
increases, but the electrons have the same energy
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Property 3: Ionization Energy the energy required to remove an
electron from a neutral atom Example Na + energy Na + + e -
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Ionization Energy - trends Group Trend Main Group General
DECREASE in ionization energy down a group Why? The electrons are
further from the nucleus, easier to remove Period Trend Main Group
General INCREASE in ionization energy across a group Why? The
charge in the nucleus increases, while the electrons have the same
energy
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Property 4: Electron Affinity the energy change that occurs
when an electron is acquired by a neutral atom Example Na + e - Na
- + energy
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Electron Affinity - trends Group Trend Main Group General
INCREASE in electron affinity down a group Why? It is harder to add
an electron to the neutral atom Period Trend Main Group General
INCREASE in ionization energy across a group Halogens have the
greatest electron affinity
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Property 5: Ionic Radii Cation A positive ion Anion A negative
ion The ionic radius is simply the radius of an ion.
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Ionic Radii- trends Group Trend Main Group General INCREASE in
ionic radii down a group Why? Cations the atom is simply bigger
Anions greater negative charge Period Trend Cations General
DECREASE as the positive charge increases Anions General DECREASE
as the negative charge decreases
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Property 6: Electronegativity a measure of the ability of an
atom in a chemical compound to attract electrons from another atom
in the compound Think of it as how much an atom will share.
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Electronegativity trends Group Trend Main Group General
DECERASE in electronegativity down a group Period Trend Main Group
General INCREASE in electronegativity across a group Note: Alkali
metals are the least electronegative group Halogens are the most
electronegative group