Transcript Chapter 2 notes

Fundamentals of General, Organic
and Biological Chemistry
7th Edition
Chapter Two
Atoms and the Periodic
Table
James E. Mayhugh
Copyright © 2010 Pearson Education, Inc.
2.1 Modern Atomic Theory
► Atoms are composed of tiny subatomic particles
called protons, neutrons, and electrons.
► Atomic masses are relative … one atom is
assigned a mass, and all others are measured
relative to it.
► The version of carbon that contains 6 protons and
6 neutrons is that atom, and it is assigned a mass
of exactly 12 atomic mass units (amu).
►Both protons and neutrons have a mass close to one
amu.
►Electrons are ~2000 times lighter than protons and
neutrons, so their relative mass is ~ 0 amu
►Protons and electrons have electrical charges that are
equal in magnitude but opposite in sign.
► The protons and neutrons are packed closely
together in a dense core called the nucleus.
Surrounding the nucleus, the electrons move about
rapidly through a large volume of space.
►The relative size
of a nucleus in
an atom is the
same as that of a
pea in the
middle of this
stadium.
2.2 Elements and Atomic Number
►Atomic Number (Z): The number of protons in
each atom of an element.
►It’s THE characteristic that defines which
element it is.
►Atoms are neutral …# of protons and # of electrons
are equal.
►# of neutrons is usually NOT equal to
protons and electrons!!
►Mass Number (A): The total number of protons
plus neutrons in an atom.
2.3 Isotopes and Atomic Weight
Isotopes:
Atoms with identical atomic
numbers (Z) but different mass numbers
(A) are called isotopes.
# of protons are the same, but # of
neutrons are different
Isotopes of a given element have
identical CHEMICAL properties, but
different NUCLEAR properties.
Isotopes of Hydrogen
Isotope Symbols
Isotope Symbols
Other methods of conveying
the same information as
Hydrogen – 3
H–3
3H
How many protons, electrons, and neutrons are in
the atom shown below?
23 5
92
U
1.
2.
3.
4.
92p, 92e, 143n
92p, 43e, 235n
92p, 92e, 235n
235p, 235e, 143n
Atomic
Weight (Mass): The weighted
average mass of all isotopes of that element
It’s the “decimal” number on the periodic table
But no single atom of that element has that
weight.
Atomic
weight=
(isotope fractional abundance)*(isotope mass)
Atomic
weight= (isotope fractional abundance)*(isotope mass)
Gallium
has two naturally occurring isotopes:
60.4% is Ga-69, (mass = 68.9257 amu), and
39.6% is Ga-71, (mass = 70.9248 amu).
Calculate the average atomic weight for
gallium.
2.4 The Periodic Table
► elements are arranged by increasing atomic
number …
► into seven horizontal rows, called periods…
► and 18 vertical columns, called groups.
► The elements in a given group have similar
chemical properties.
The Periodic Table
The groups on the periodic table are divided into three
main categories.
►Main Groups: The two groups on the far left (1-2)
and the six on the far right (13-18) are the main groups.
The groups on the periodic table are divided into three
main categories.
►Transition Metal Groups: Elements in the groups
numbered 3 through 12.
The groups on the periodic table are divided into three
main categories.
►Inner Transition Metal Groups: The 14 groups
shown at the bottom of the table that are not numbered
containing the Lanthanides and the Actinides.
2.5 Names of Different Groups

Group 1A or 1 Alkali
metals
2.5 Names of Different Groups

Group 2A or 2 Alkaline
Earth metals
2.5 Names of Different Groups

Group 7A or 17 Halogens
2.5 Names of Different Groups

Group 8A or 18 Noble
Gases
2. 6 Electronic Structure of Atoms
Quantum mechanical model
► Gives specific information about what the
electrons are “doing” in the atom
► And where their
“playgrounds” are
The “planetary” model - too simplistic.
Electrons do NOT orbit the nucleus like planets
orbit the sun.
7.5
Quantum Mechanical Model
Better model: electrons in a PLAYGROUND
with a fence where the train track was.
We call each “playground” an orbital
7.5
Electronic Structure of Atoms
► Old school:
► New school: electrons flying around in “orbitals”
that extends OUT to where that circle was drawn.
Electron Orbitals
A 3-D region in space where you are most likely
to find a given electron
If you could see the electron, this region would
look like a 3-D “blur”… we also call this an
“electron cloud”
There are LOTS of these “electron playgrounds”
in an atom… and they overlap!
7.5
2. 6 Electronic Structure of Atoms
OK… now for the “Nitty Gritty” of
how electrons are organized in an atom:
► The electrons “fly around” in a 3-D region
called an orbital.
► 2 Electrons MAX can “fit” into any
given orbital, and they spin in
opposite directions.
► The SIZE of the orbital is determined
by the ENERGY SHELL of the electron
► The SHAPE of the orbital is determined
by the ENERGY SUBSHELL of the
electron.
Energy Shells
► (Also known as energy levels)
► The higher the energy level of the
electron, the bigger its shell
► Shells are made up of one or more subshells.
Energy SUBshells
► (Also known as energy sublevels)
► The SUBshell is the set of “playgrounds”
(orbitals) in a given shell.
► Therefore, they all extend the same
distance from the nucleus as each other
Energy SUBshells
► Orbitals (the electron “playgrounds”) of a
given subshell all have identical (or at least
very similar) shapes.
► There are four different types of subshells,
labeled as: s, p, d, and f,
► each with different shapes
► “Shapes” of orbitals in a given subshell:
So… what do we have so far?
► Electrons “fly” around the nucleus in “playgrounds”
called…
► Orbitals, (which can hold no more than 2 electrons,
each) whose shapes are determined by which…
► Subshell that the electron is in, whose size is
determined by which…
► Shell the electron is in.
► And an atom is simply a collection of electrons that
are in these shells/subshells/orbitals
► But WAIT… there’s MORE!!! 
# of Subshells per Shell
► A shell has a number of subshells equal to its
shell number.
► The first subshell in ANY shell is always “s”
because it is lowest in energy.
► The next subshell is always “p”, etc.
# of Orbitals per Subshell
► The more “complex” the subshell shape, the
more orbitals that subshell has.
# of Orbitals per Subshell
► The more “complex” the subshell shape, the
more orbitals that subshell has.
► The number of orbitals within a subshell
increases by odd numbers.
S Subshell
-Only
one
orbital… so the
orbital is the
whole subshell!
7.5
p Subshell Orbital Orientations
-3
double lobe orbitals in a p
subshell… one along each axis
7.5
d Sublevel Orbital Orientations
-The
more complicated
the shape, the more
possible orbitals!
7.5
f Sublevel Orbital Orientations
-The
more complicated
the shape, the more
possible orientations!
7.5
Summary!!
2.7 Orbital Diagrams and Electron
Configurations
Orbital Diagram: A “tool” used to show location
and other information about each electron in an
atom
Electron Configuration: A “shorthand” version of
an orbital diagram
2.7 Orbital Diagrams and Electron
Configurations
“Quantum World” Rules
1. Electrons occupy the lowest energy orbitals
available first.
2. 2 electrons, max, per orbital
3. For all p, d and f subshells, each orbital gets one
electron (spinning the SAME direction) before
any orbital gets two.
Order of energy sublevels:
►Some overlap in energy
levels occurs starting with
shells 3 and 4.
You will need to build a mnemonic device for
remembering the order of the energy levels in an
atom.
Orbital Diagram and Electron Configuration Practice
“Shorthand” electron configuration for lead (Pb)
1. Write the symbol for the previous noble gas in
brackets:
[Xe]
2. “Pick up” the configuration on the diagonal chart
from the “s” subshell of the row number lead is in:
[Xe] 6s
3. Subtract # of electrons in Xe from those in lead, and
place those remaining electrons: 28 more e- needed
[Xe] 6s24f145d106p2
-2.8 Valence Electrons
•
Valence electron: An electron in the outermost
(valence) shell of an atom.
•
•
•
These electrons are the ones that would
interact first with the electrons of a different
atom…
…so they are the most important ones to
“keep track of”.
(as opposed to “inner shell” or “core”
electrons)
Valence Electrons
•
How many valence electrons in:
•
10Ne
•
20Ca
•
31Ga
2.8 Electron Configuration and the Periodic
table
•
•
•
•
•
•
•
Review Question:
What determined which
elements where placed in columns with each other?
They all behaved similarly.
Let’s use the electron configurations of the alkali
metals to see why:
22s1
Li
1s
3
22s22p63s1
Na
1s
11
22s22p63s23p64s1
K
1s
19
22s22p63s23p64s23d104p65s1
Rb
1s
37
Valence Electrons
•
•
•
Elements with the same number of valence
electrons behave similarly to each other.
Let’s look for a pattern to quickly determine the
number of valence electrons in any MAIN
GROUP element.
The “one’s place” of the group number of the
MAIN GROUPS is the number of valence
electrons of the elements in that column.
2.8 Electron Configuration and the Periodic
table
►The periodic table can be divided into four regions or
blocks of elements according to the subshells that
are last to fill, s, p, d, or f.
Visual method to recall the order of orbital filling.
2.9 Electron-Dot Symbols
►Electron-dot symbol: An atomic symbol with dots
placed around it to indicate the number of valence
electrons.
End of Chapter 2
Hydrogen has three isotopes: H-1, H-2, and H-3, and
has an average atomic mass of 1.00794 amu. Which
isotope is most abundant?
1.
2.
3.
4.
The three isotopes of hydrogen are equally
abundant.
H-1
H-2
H-3
Hydrogen has three isotopes: H-1, H-2, and H-3, and
has an average atomic mass of 1.00794 amu. Which
isotope is most abundant?
1.
2.
3.
4.
The three isotopes of hydrogen are equally
abundant.
H-1
H-2
H-3
The orbitals illustrated below are
1.
2.
3.
4.
s orbitals.
p orbitals.
d orbitals.
f orbitals.
The orbitals illustrated below are
1.
2.
3.
4.
s orbitals.
p orbitals.
d orbitals.
f orbitals.
What is the electron configuration of the period 4
group 7A element?
1.
2.
3.
4.
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
3p6 4s2 3d5
3p6 4s2 4d5
3p6 4s2 3d104p5
3p6 4s2 4d104p5
What is the electron configuration of the period 4
group 7A element?
1.
2.
3.
4.
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2
3p6 4s2 3d5
3p6 4s2 4d5
3p6 4s2 3d104p5
3p6 4s2 4d104p5
The number of unpaired electrons contained in an
atom of an element in the group indicated in red on
the periodic table below is
1.
2.
3.
4.
zero.
two.
four.
six.
The number of unpaired electrons contained in an
atom of an element in the group indicated in red on
the periodic table below is
1.
2.
3.
4.
zero.
two.
four.
six.
The number of valence electrons contained in an
atom of the element indicated in blue on the periodic
table below is
1.
2.
3.
4.
zero.
two.
four.
six.
The number of valence electrons contained in an
atom of the element indicated in blue on the periodic
table below is
1.
2.
3.
4.
zero.
two.
four.
six.
Elements belonging to the group of elements
indicated on the periodic table below are known as
the
1.
2.
3.
4.
alkali metals.
alkaline earth
metals.
halogens.
noble gases.
Elements belonging to the group of elements
indicated on the periodic table below are known as
the
1.
2.
3.
4.
alkali metals.
alkaline earth
metals.
halogens.
noble gases.
What is the outer-shell electron configuration of
elements in the group indicated on the periodic table
below?
1.
2.
3.
4.
ns2
np2
nd2
ns2 (n–1)d2
What is the outer-shell electron configuration of
elements in the group indicated on the periodic table
below?
1.
2.
3.
4.
ns2
np2
nd2
ns2 (n–1)d2
The element having chemical properties most similar
to As is
1.
2.
3.
4.
S
Sb
Se
Si
The element having chemical properties most similar
to As is
1.
2.
3.
4.
S
Sb
Se
Si
How many dots are in the electron-dot structure of
boron?
1.
2.
3.
4.
One
Three
Five
Seven
How many dots are in the electron-dot structure of
boron?
1.
2.
3.
4.
One
Three
Five
Seven
How many dots are in the electron-dot structure of
the oxide ion, O2–.?
1.
2.
3.
4.
Four
Six
Eight
Ten
How many dots are in the electron-dot structure of
the oxide ion, O2–.?
1.
2.
3.
4.
Four
Six
Eight
Ten
Of the four types of electromagnetic radiation given,
which has the most energy?
1.
2.
3.
4.
Infrared
Microwaves
Ultraviolet
Visible light
Of the four types of electromagnetic radiation given,
which has the most energy?
1.
2.
3.
4.
Infrared
Microwaves
Ultraviolet
Visible light