Wednesday September
2012
th
19 ,
Today:
•Review
•Quiz 3
•Finish Chapter 3
Frequency: CD
Periodic Table
22
Dalton’s Atomic Theory
Dalton theorized that Atoms
 are tiny particles of matter too
small to see,
 are able to combine with
other atoms to make
compounds, and
 are similar to each other for
each element and different
from atoms of other elements.
A chemical reaction is the
rearrangement of atoms.
Images of nickel atoms
are produced when nickel is magnified
millions of times by a scanning
tunneling microscope (STM). This
instrument generates an image of
the atomic structure.
Subatomic Particles
Atoms contain subatomic
particles such as
 Protons, which have a
positive (+) charge;
 electrons, which have a
negative (–) charge; and
 neutrons, which have no
charge.
Experiments show that like
charges repel and unlike
charges attract.
44
Structure of the Atom
An atom consists of
 a nucleus that
contains protons
and neutrons, and
 electrons in a large,
empty space around
the nucleus.
55
Isotopes
Isotopes
 are atoms of the same element that have different mass
numbers.
 have the same number of protons but different numbers
of neutrons.
 can be distinguished by atomic symbols.
Quiz 3
Clickers!!
Question 1:
The positive subatomic particle is called a?
a) Neutron
b) Positron
c) Proton
d) Electron
Question 2
If Oxygen has an atomic number of 8 and 10
neutrons, what is the mass number?
a) 2
c) 16
b) 18
d) 15.99
Question 3
If Calcium has an atomic number of 20, how
many electrons are in the neutral atom?
a) 18
c) 20
b) 19
d) 21
Question 4
The bulk of an atom’s density is located where?
a) Nucleus
c) Proton
b) Neutrons
d) Electrons
Question 5
The bulk of the atom’s volume is made up of
what?
a) Neutons
c) Protons
b) Nucleus
d) Electrons
Question 6
What part of Dalton’s atomic theory was proven
incorrect?
a) Atoms are tiny particles of matter too small
to see.
b) Atoms combine with other atoms to make
compounds.
c) Atoms are similar to each other for each
element.
d) Atoms are different from atoms of other
elements.
Question 7
Mega is the metric prefix that means what?
a) 102
c) 103
b) 10-3
d) 106
Question 8
μ is the metric prefix that means what?
a) 10-2
c) 103
b) 10-3
d) 10-6
Question 9
How many significant figures are in 0.0056?
a) 1
c) 3
b) 2
d) 4
Question 10
How many Significant Figure should the
following problem have?
22.1 x 1.458 =
a) 1
c) 3
b) 2
d) 4
Question 11
Which of the following is a correctly written
isotope of carbon?
2
a) 6
c) 126
C
C
6
b) 12
C
d) 6 C
Electrons!
Electron Energy Levels
Electron energy levels increase
in energy and number as
electrons get farther away from
the nucleus.
The higher the electron energy
levels,
 the more electrons they hold.
 the more energy the electrons
have.
Energy Levels and Sublevels
Orbitals
Each electron sublevel consists of orbitals, which
 are regions where there is the highest probability of
finding an electron.
 have their own unique three-dimensional shape.
 can hold up to 2 electrons.
Electron Capacity in Sublevels
Energy Diagram for Sublevels
Orbital Diagrams
An orbital diagram shows
 orbitals as boxes in each sublevel.
 electrons in orbitals as vertical arrows.
 electrons in the same orbital with opposite spins (up and
down vertical arrows).
Example:
Orbital diagram for Li
1s2
2s1
filled half-filled
2p
empty
Learning Check
Write the orbital diagrams for each of the following:
1. nitrogen
2. oxygen
3. magnesium
Electron Configuration
An electron configuration
 lists the filled and partially filled energy levels in order of
increasing energy.
 lists the sublevels filling with electrons in order of increasing
energy.
 uses superscripts to show the number of electrons in each
sublevel.
 for neon is as follows: number of electrons = 10
1s22s22p6
Abbreviated Configurations
In an abbreviated configuration,
 the symbol of the noble gas is in brackets, representing
completed sublevels.
 the remaining electrons are listed in order of their sublevels.
Example: Chlorine has the following configuration:
1s22s22p63s23p5
[Ne]
The abbreviated configuration for chlorine is
[Ne]3s23p5.
Learning Check
1. The correct electron configuration for nitrogen is
A. 1s22p5
B. 1s22s22p6
C. 1s22s22p3
2. The correct electron configuration for oxygen is
A. 1s22p6
B. 1s22s22p4
C. 1s22s22p6
Learning Check
Write the electron configuration and abbreviated
configuration for each of the following elements:
1. Cl
2. S
Electron Configurations and the
Periodic Table
The periodic table consists of sublevel blocks
arranged in order of increasing energy.
 Groups 1A and 2A
= s block
 Groups 3A to 8A
= p block
 Transition Elements
(This sublevel is (n-1), 1 less
than the period number.) = d block
 Lanthanides/Actinides
(This sublevel is (n-2), 2 less
than the period number.) = f block
Sublevel Blocks
Guide to Using Sublevel Blocks
Writing Electron Configurations
Using the periodic table, write the electron configuration
for silicon.
Solution:
Period 1
Period 2
Period 3
1s block
2s → 2p blocks
3s → 3p blocks
1s2
2s2 2p6
3s23p2 (at Si)
Writing all the sublevel blocks in order gives the
following:
1s22s22p63s23p2
Electron Configurations of the d Level
The 4s orbital has a lower energy than the 3d orbitals.
Writing Electron Configurations
Using the periodic table, write the electron configuration
for manganese.
Solution:
Period 1
1s block
1s2
Period 2
2s → 2p block
2s2 2p6
Period 3
3s → 3p block
3s2 3p6
Period 4
4s → 3d block 4s2 3d5 (at Mn)
Writing all the sublevel blocks in order gives the
following:
1s22s22p63s23p64s23d5
Valence Electrons
The valence electrons
 determine the chemical properties of the elements.
 are the electrons in the outermost, highest energy level.
 are related to the group number of the element.
Example: Phosphorus has 5 valence electrons.
5 valence
electrons
P Group 5A(15)
1s22s22p63s23p3
Learning Check
Identify the number of valence electrons for each of the
following:
1. O
A. 4
B. 6
C. 8
2. Al
A. 13
B. 3
C. 1
3. Cl
A. 2
B. 5
C. 7
Learning Check
Identify the number of valence electrons for each of the
following:
1. 1s22s22p63s23p1
2. 1s22s22p63s2
3. 1s22s22p5
Electron-Dot Symbols
An electron-dot symbol
 indicates valence electrons
as dots around the symbol of the
element.
 of Mg shows two valence electrons
as single dots on the sides of the
symbol Mg.
Mg
Mg
Mg
Mg
Mg
Writing Electron-Dot Symbols
The electron-dot symbols for
 Groups 1A (1) to 4A (14) use single dots:
Na
Mg
Al
C
 Groups 5A (15) to 7A (17) use pairs and single dots:
P
O
Cl
Learning Check

1. X is the electron-dot symbol for
A. Na
B. K
C. Al

2.

X  is the electron-dot symbol for

A. B
B. N
C. P
Atomic Size
Atomic size
 is described using the atomic radius.
 is the distance from the nucleus to the valence electrons.
 increases going down a group.
 decreases going across a period from left to right.
Atomic Radius
Learning Check
Select the element in each pair with the larger atomic
radius.
1. Li or K
2. K or Br
3. P or Cl
Ionization Energy
Ionization energy
 is the energy it takes to remove a valence electron from an
atom in the gaseous state.
Na(g) + Energy (ionization)
Na+(g) + e–
 decreases down a group, increasing across the periodic table
from left to right.
Ionization Energy and Valence Electrons
Ionization Energy
The ionization
energies of
 metals are low.
 nonmetals are high.
Friday
• Group Assignment
• Next week’s Lab: Lab #3 – Nuclear Chemistry