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CHAPTER 7: PERIODIC PROPERTIES OF THE ELEMENTSExploration of important properties of elements across a row or down a column.
JANUARY 2ND, 2013
Do Now:Take out your homework, compare
your answers to a neighbor.
FROM MENDELEEV TO MOSELEY
1869: Mendeleev arranged elements by atomic mass Noted similarities, forced to leave holes in PT
1913: Moseley Developed concept of atomic numbers Bomabrded elements with high-energy electrons
Unique frequency Correctly identified atomic number as number of
protons
EFFECTIVE NUCLEAR CHARGE
Where do many of the properties of atoms originate?
How does Coulomb’s law relate to effective nuclear charge?
As we get further from the nucleus, how is our effective nuclear charge effected?
EFFECTIVE NUCLEAR CHARGE CONT.
Why is analyzing the effective nuclear charge precisely problematic?
How do we estimate these interactions?
EFFECTIVE NUCLEAR CHARGE
Zeff = Z − S
where: Z = atomic number S = a screening
constant (usually close to the number of inner electrons)
TRENDING
How does effective nuclear charge change across a period?
Why?
How does effective nuclear charge change down a period?
Van der Waals Radius (Non-bonding radius): is the radius of an atom when it is bonded to another atom by van der Waals forces.
Covalent atomic radius(Bonding radius): is half the distance between two atoms covalently bonded.
ATOM SIZE
Had students read 7.4 in the textbook and then had class discussion
JANUARY 3RD, 2012
Do Now:
In terms of effective nuclear charge, explain the atomic radius trend both across a period and down a group.
Arrange the following isoelectronic series in decreasing atomic size: K+, Cl-, Ca2+, S2-
IONIZATION ENERGY
Define Ionization Energy.
How do we differentiate between 1st and 2nd ionization energies?
How is the difficulty of removing an electron correlated with ionization energy?
TRENDING!
I1 < I2 < I3 , Why?
How is the ionization energy affected w/ removal of electrons from an inner shell?
Page 259 (table)
TRENDING CONT.
How does ionization energy trend from left to right across a period?
How about down a group?
Generally, s + p block show larger range in values for ionization energy. The d block increases minimally. The f, very little.
PRACTICE
Which has a higher third ionization energy, Ca or S? Why?
Why does Boron have a lower ionization energy than Beryllium?
Why is it easier to remove a 2p electron from oxygen than from nitrogen?
JANUARY 4TH, 2012
DO NOW : Arrange the following atoms in order of
increasing ionization energy: Neon, Sodium, Phosphorus, Argon, and
Potassium.
Arrange the following atoms in order of decreasing ionization energy: Boron, Aluminum, Carbon, and Silicon
SO HOW DOES IONIZATION WORK?
When electrons are removed from an atom, they are removed from occupied orbital with highest principle quantum number. IE: Lithium.
Try removing 2 electrons from Iron. How about a third?
Try removing 2 electrons from Tin. How about 4?
PRACTICE
Write the electron configurations for the following:
Ga3+
Cr3+
Br-
AWKWARD?
Why is using ionization energy “awkward” when talking about forming an anion?
Instead, we use the term “electron affinity”!
Energy is released when adding an electron. How would we represent this numerically?
HOW DOES THIS ALL TIE TOGETHER?
How can we differentiate between ionization energy and electron affinity?
What does the electron affinity of a noble gas look like?
PREDICTIONS!
Predict which group would have the most negative electron affinities. Why?
What is the relationship between the value of the first ionization energy of Cl-(g) and the electron affinity of Cl(g)?
BROADLY SPEAKING… Elements organized as metals, nonmetals,
metalloids. Metals:
Luster; various colors although mostly silver Solids malleable and ductile Good conductors Most metal oxides are solids that are basic Tend to form cations in aqueous solution
Non Metals: No luster, various colors Solids usually brittle; some hard, some soft. Poor conductors Most nonmetal oxides are molecular substances that
form acid solutions Tend to form anions in aqueous solution
METALLIC CHARACTER
Where is the “most” metallic metal located on the periodic table?
What is the general trend for metallic character based on this information?
METALS
Which metals is a liquid at room temperature?
How can we use first ionization energy to characterize metals vs. nonmetals?
Why are most metal oxides basic?
METAL OXIDES
Most metal oxides are basic.
Metal Oxides + Water Metal Hydroxide
IE: Na2O (s) + H2O (l) 2 NaOH (aq)
Due to oxide ion, which reacts with water.
IE: O2- (aq) + H2O (l) 2 OH- (aq)
Insoluble metal oxides react with acids to form salt plus water.
IE: NiO (s) + 2 HNO3 (aq) Ni(NO3)2 (aq) + H2O (l)
PRACTICE
Would you expect scandium oxide to be a solid, liquid, or gas at room temperature? Write the balanced chemical equation for the
reaction of scandium oxide with nitric acid.
Write the balanced chemical equation for the reaction between copper (II) oxide and sulfuric acid.
NON METALS
How can non-metals exist at room temperature?
Why are most non-metal oxides acidic?
Nonmetal oxide + water acid
Most nonmetal oxides dissolve in basic solutions to form salt and water.
PRACTICE
Write the balanced chemical equation for the reaction of solid selenium dioxide with the following: Water Aqueous sodium hydroxide
Write the balanced chemical equation for the reaction of solid tetraphosphorus hexoxide with water.
