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8/6/2019 Trends in 3rd Period
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Third-Period Trends
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Elements in the 3rd Period
SodiumMagnesium
AluminumSilicon
Phosphorus
Sulfur ChlorineArgon
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Trends in what?In their chemical reaction with OXYGEN, WATER,AND CHLORINE
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Some Observations
• The elements are arranged according to
increasing proton number. (valence electrons
increase).
• Atomic radii decrease (smaller volume).
• Ionization energies increase.
• Elements become less metallic.
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Some Observations
• Na, Mg, and Al have good thermal and
electrical conductivities. The metalloidSi is only a fair conductor of heat andelectricity, while the nonmetals P, S, Cl,
and Ar are poor conductors.• Metallic property decreases.
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Some Observations
• Their valence electrons occupy the 3sand 3p orbitals.
• Electronegativity increases. (tendencyof atoms to attract electrons towardsitself)
• Elements in each period have electronsin the same outer shell.
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It requires more energy to strip an electronfrom the lower energy 3s orbital in Mg than
from a half-filled 3p orbital in Al.
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The Melting and BoilingPoints
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Explanation
• Melting: it depends on the attractive
forces holding the particles together
whether or not the particles can beseparated easily or not (needed energy)
• Boiling: similar to melting, the
attractive forces on the particles (more
energy or not)
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Melting, Boiling, Hardness
• depends on the strength of the
attractive forces acting upon the atom
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Structure AFFECTS meltingand boiling points.
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amphotericGreek word “amphos”Meaning: both
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metallic bonds (Na, Mg, Al)covalent bonds (Si)
intermolecular forces (P, S, Cl, Ar)
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The Forces
• Metallic Bonds (Na, Mg, Al) - become
stronger, hence increasing melting and
boiling points
• Covalent (Si) - crystalline solid
• Intermolecular forces - attractive forces become progressively weaker
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Definitions
• Oxide: a binary compound of oxygenwith another element or group
• Chloride: a compound of chlorine with
another element or group
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Oxides
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Silicon oxide:
diamond-likemacromolecular structure with a
high melting and
boiling point
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hl d
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Chlorides
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d hl d d
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Aluminumchloride possesses
a much morecovalent
character.
Sodium chloride and magnesiumchloride are ionic and still haverelatively high melting points.
The three remainingchlorides are held
together by weak van
der Waal’s forces,therefore low meltingand boiling points.
van der Waals forces |ˈvan dər
ˌwôlz, -ˌvälz|
pluralnounChemistry
weak, short-range electrostaticattractive forces betweenuncharged molecules, arising from the interaction of permanent or transient electricdipole moments.
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• Sodium chloride (only neutral chloridein Period 3 - gives a pH of 7 when
dissolved in distilled water)
• Magnesium chloride gives a slightlyacidic solution with distilled water (Mg
ion is small, and charge of +2 - density
of the charge of the ion is much higherthan that on a sodium ion)
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• Aluminum chloride (no water or
anhydrous), when added to water,
gives an exothermic reaction and HCl is
produced.
• Chlorine reacts with water to form an
acidic solution.
Cl 2 (aq)+ H 2O(l ) HCl (aq) + HClO(aq)
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Reference Sources• http://scienceaid.co.uk/chemistry/inorganic/period3.html
• http://www.docbrown.info/page07/ASA2ptable5b.htm
• http:/ /www.chemguide.co.uk/ inorganic/per iod3/oxidesphys.html
• http://chemistry-helper.blogspot.com/2011/04/3-periodicity-sl.html
• http://sandblastingabrasives.com/aluminum-oxides-3/
• http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html
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Reference Sources
• http://www.ausetute.com.au/trendpd3.html
• http://www.chemguide.co.uk/inorganic/period3/
elementsphys.html• http://ibchem.com/IB/ibnotes/brief/per-hl.htm#pert
• http://www.creative-chemistry.org.uk/alevel/
module1/trends8.htm• h t t p : / / c h e m i s t r y . a b o u t . c o m / o d /
periodictableelements/a/periodictrends.htm
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Reference Sources• http://www.chemguide.co.uk/atoms/structures/
period3.html
• http://www.avon-chemistry.com/p_table_lecture.html
• http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Electronic_Configurations
• http://chemwiki.ucdavis.edu/Inorganic_Chemistry/
D e s c r i p t i v e _ C h e m i s t r y /P e r i o d i c _ T a b l e _ o f _ t h e _ E l e m e n t s /Periodic_Properties_of_the_Elements
• h t t p : / / w w w . e n i g m a t i c - c o n s u l t i n g . c o m /