HNRS 227 Lecture 11 Chapter 8 and Chapter 9
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Transcript HNRS 227 Lecture 11 Chapter 8 and Chapter 9
HNRS 227 Lecture 11
Chapter 8 and Chapter 9
The Periodic Table and Chemical Reactions
presented by Prof. Geller with materials
from Prof. Taylor
Recall from Chapter 8
History of atomic theory
Electron and nucleus (protons and neutrons in
nucleus both made up of quarks)
The Bohr Model of the Atom
The Quantum Concept
Bohr’s Theory
Quantum Mechanics
Quantum numbers
Principal, angular momentum, magnetic, and spin
Electron Configuration
Pauli Exclusion Principle
Filling of orbital shells
Periodic Table of Elements
An underlying principle
most stable state for an atom is one in which
the outermost shell is filled with the maximum
number of electrons
1st Shell (1 orbit; 2 electrons)
Hydrogen (11H; 1 electron; stable ?)
Helium (24He; 2 electrons; stable ?)
Periodic Table’s 1st Row
Hydrogen and Helium
Periodic Table of Elements
2nd shell has 4 orbits with 2 electrons
(maximum) per orbit (total of 8
electrons/shell)
Most stable configuration is the following:
1st shell filled with 2 electrons
2nd shell filled with 8 electrons
Total of 10 electrons (1020Ne)
2nd row of Periodic Table
8 elements (list and relate to the above)
Periodic Table of Elements
3nd shell has 4 orbits with 2 electrons
maximum per orbit (total of 8
electrons/shell)
Most stable configuration is the following:
1st shell filled with 2 electrons
2nd shell filled with 8 electrons
3rd shell filled with 8 electrons
Total of ___ electrons (1840Ar)
3nd row of Periodic Table
8 elements (list and relate to the above)
Periodic Table of Elements
Rows
Number of elements in a row is not chance
but reflects the maximum number of electrons
in the outermost shell
Row
Row
Row
Row
etc
1
2
3
4
=
=
=
=
2
8
8
18
Periodic Table of Elements
Columns
Elements in a given column have similar
chemical properties
All elements in column have the same number
of valence electrons
Column IA has 1 electron in outer shell
Column IIA has 2 electrons in outer shell
Column IIIA has 3 electrons in outer shell
Column IVA has 4 electrons in outer shell
Column VA has 5 electrons in outer shell
Periodic Table of Elements
Taylor’s Take Home Message
Atoms are the chemical building blocks of all matter
Structure of atoms (electrons, neutrons, protons and
their arrangement) determine the unique
behavior/attributes of the elements
Of the above (No. 2), the “place” and “pairing” of the
electrons are the most critical in chemical reactions
Electrons reside in defined shells (orbits) surrounding the
nucleus of the atom and the electrons in the outermost
shell (valence electrons) determine an atom’s chemical
reactivity
Utility and periodicity of the Periodic Table of Elements is
a function of the distribution of all electrons in shells, the
valence electrons in the outermost shell, and the mass of
the element
Chemical Reactions and Bonds
Chapter 9
Review valence electrons
Principles of “Bonds Away”
Ionic Bonds
Metallic Bonds
Covalent Bonds
Intermolecular Forces
Common Chemical Reactions
Taylor’s Take Home Message
When atoms combine to produce molecules and
compounds, expect the chemical properties of the
molecules/compounds to be far different than that of the
constituent atoms (hierarchy theory)
Atoms bind together by re-arranging and sharing
electrons
Ionic bonds
Metallic bonds
Covalent Bonds
Intermolecular forces (e.g., hydrogen bond)
Chemical interactions make and break bonds between
atoms and in so doing effect a change in energy
(potential and kinetic)
Weak chemical bonds (e.g., covalent bonds) play a very
important role in the chemistry of life
Chapter Items that won’t be
emphasized from Chapter 9
p. 184
A Closer look
p. 186
A Closer Look
pp. 188-191
Percent Composition of Compounds
Ion Exchange Reactions
Atoms in Proximity:
Chemical Bonds
Chemical Action
when two atoms are brought together,
electrons will tend to re-arrange themselves to
the lowest energy state where the valence
electrons are most stable
Chemical Reaction
electrons are re-arranged into bonds
Give away electrons
Accept electrons
Share electrons
Ionic Bonds
Some atoms give away electrons
whereas other atoms receive
electrons
Example of lithium (Li) chloride (Cl)
3 Li
6
+
17
35.5Cl
= LiCl
Ionic Bonding
Lithium (Li)
Li gives up 1 electron and is left with 2 electrons (-) and 3 protons (+); net
positive (+) charge
Chlorine (Cl)
Cl has 1 unpaired electron in valence shell, so Cl tends to accept an electron
and is left with 18 electrons (-) and 17 protons; net negative (-) charge
Ionic Bonding Summary
Some atoms give away electrons while other atoms
receive electrons
Example of lithium chloride
Li + Cl = LiCl
Bonding via electrical attraction between Li+ and ClLi+ + Cl - = Li+Cl-
Consequence: ionic bonds are underpinned by charged
ions and tend to form crystals of very specific and
repeating geometry (very rigid)
Example: NaCl is based on ionic bonds and is salt
Ionic Bond Example: Salt
Metallic Bonds
Some elements do not give or take electrons
(ionic bonds) BUT share electrons
Valence electrons tend to move freely between
both atoms (contrast with ionic bonds)
Significance of sharing electrons: compounds
tend to show two features
Malleability (easily worked or pounded)
Conductive of electricity (good conductors)
Examples
Gold jewelry
Copper wire
Covalent Bonds
Extremes of behavior in bonding
Accept or give away electrons (ionic bonds)
No tendency to share (noble gases)
Intermediate between these two extremes but
Do not form ionic bonds
Do not form metallic bonds
Yet share 1, 2, 3 and 4 electrons in unique
arrangement called covalent bonds
Key: orbits of valence electrons are shared so that electrons
are shared (and move) between valence shells of adjacent
atoms
Covalent Bond Example
Example of hydrogen fluoride (HF)
11H and 919F
Note: Valence shell for both atoms are full
Single bond shared
Double bond
Covalent Bonds with Carbon
612C is a special case (profoundly important)
Valence electrons for C are 4 (1 in each orbit) and
intermediate between giving and accepting
C - C single covalent bond (1 orbit)
C
C - C two covalent bonds involving 2 orbits
Unique behavior of C
C
C-C-C
(or H or N or __)
C
Behavior of Valence Electrons
Five Options
No action (e.g., inert gases)
Give away one or more electrons in valence
state (positive ion leading to ionic bond)
Accept one or more electrons to valence state
(negative ion leading to ionic bond)
Share an electron with many other atoms
without respect to an orbit (metallic bond)
Share one or more electrons plus their orbits
with another atom (covalent bond)
Regarding Next Week’s Lab:
Evaporation and Chemical Structure
Vaporization and chemical properties of
molecules
Liquid to gas state change
State change has energy cost: endothermic
(temperature decrease)
Temperature change is a function of
chemical structure of molecule
Bonding and polarity
Evaporation and Chemical Structure
Organic compounds
Carbon based or hydrocarbons bond with other
elements via covalent bonds)
Alkanes: C and H only
• Pentane (C5H12)
Alcohols: C, H and OH (hydroxyl group)
• Ethanol (C2H5OH)
• Structural formula
Hydrogen bonding: H bonded to N, O or F (tight
bond)
Process: as chemical vaporizes, temperature
change is chemical specific and is a “window”
onto the chemical structure of molecule
Evaporation and Chemical Structure
Hypothesis
temperature changes with vaporization in a
manner that is predictable, based on the
bonding among atoms involving C, H and OH
Method
Measure temperature change electronically
Record for 6 hydrocarbons
Analyze data (graphically) based on
understanding of the bonds for each molecule
Intermolecular Forces:
Polarization & Hydrogen Bonding
Example of water (H2O)
+H
H+
O When one molecule’s distribution of atoms results in one
side of the molecule having either a + or – charge
Resulting distribution of charges causes adjoining H2O
molecule to align itself with + and – charges to be most
stable
Called “polarity” of molecule (e.g., magnet)
Relate to lab exercise: greater polarity, greater bonding
and less evaporation (less temperature change)
Intermolecular Forces: Van
der Waal Forces
In polarity, specific and rigid + and – fields on
each molecule that does not change over time
When molecules converge, inevitable that
electrons shift and re-distribute (e.g., planar
compound)
In re-distribution, small net attraction between
molecules arise and two molecules for weak
bond
Graphite pencil lead
Stack of paper
Acid – Base Reaction:
Measurement
pH scale
Any increase in H+ results in more acid solution
from 7 to 0
Any increase in OH- results in more basic
solution from 7 to 14
Examples
Rainwater of 5.6 means what?
Cell pH value of 6-8 means what?
Importance to biological systems and buffering
Taylor’s Take Home Message
When atoms combine to produce molecules and
compounds, expect the chemical properties of the
molecules/compounds to be far different than that of the
constituent atoms (hierarchy theory)
Atoms bind together by re-arranging and sharing their
electrons
Ionic bonds
Metallic bonds
Covalent Bonds
Intermolecular forces (e.g., hydrogen bond)
Chemical interactions make and break bonds between
atoms and in so doing effect a change in energy
(potential and kinetic)
Weak chemical bonds (e.g., covalent bonds) play a very
important role in the chemistry of life