Chapter 3 Atoms and Elements _po

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					Chapter 3   Atoms and Elements
Structure of the Atom
Reminder: Atoms lose e- to form positive ions

Reminder: Atoms gain e- to form negative ions

Let’s look at lithium atoms for example……

Compare the size of the Li atom to its nucleus

Let’s Practice Naming Elements

Write the chemical symbol for each element

The Periodic Table
The periodic table is a graphical
representation of the elements in periods
(rows) and groups (columns)
Periodic law says elements within the
same group will have similar chemical
Let’s look at Na and K metals in
the alkali metals group

(see videoclip on Na and K in
water during lecture)

Both metals react violently with water
Metals and Nonmetals
                    Nonmetals tend to powders
Metals are shiny.   or gases.
Which one of the following is a nonmetal?

a. Sn

b. Pb

c. Se

d. Zn
Physical Properties: Name the two
classifications represented by the two colors.
Special Names: Give the special name for
each color.
Electronic Properties: Name the four
classifications represented by the four colors.
Reminder: The structure of an atom can
be determined from its atomic number
and mass number.
Give the number of protons, electrons,
and neutrons in the following elements

a. P

b. H

c. K

Caves where the
Dead Sea Scrolls
were found.
Carbon-14 was used to date the Dead
Sea Scroll shown here , ~ 2000 years old .
Carbon-14 was used to date the moon
rocks shown here , ~ 4 x 109 years old .
An isotope is an atom with the same
atomic number as another atom but…….

…….a different atomic mass.

Isotopes have the same number of protons and
electrons but a different number of neutrons.
Carbon Isotopes
Magnesium Isotopes

Chlorine Isotopes

Notations Used to Represent Isotopes
This is an Isotope Symbol
1. Write the isotope symbol for

2. Repeat for magnesium-26
Atomic Mass Unit
What unit is associated with the
atomic mass of an element?
The unit associated with atomic
mass is a relative unit called the
atomic mass unit.
What is an atomic mass unit (amu) ?

An amu is a relative unit ( i.e. relative to the
mass of a carbon atom)

One amu is the mass of a carbon-12
atom divided by 12.
The mass of a carbon-12 atom is
2.085 x 10-23 g,

so 1 amu = 2.085 x 10-23 g / 12

            = 1.6738 x 10-24g
Electron Shells, Subshells, and Orbitals
How are electrons arranged in an atom?

Electrons are arranged in specific
probability regions (i.e. shells, subshells,
and orbitals) according to their energies.

Organizational Structure of the Space Outside
the Nucleus of an Atom .
A Useful Analogy is the Organization
of Space in a Building

 The electron’s address would be 1s1
How many subshells are in a shell?

Shell 1 :   s
Shell 2 :   s, p
Shell 3 :   s, p, d
Shell 4 :   s, p, d, f
You can see that the number of subshells in
a shell is the same as the number of the shell.

The letter n here represents the shell number
How many orbitals are in a subshell?
This is one s orbital in the s subshell.

Spherical shape
Notice the increase in
size from shell 1 to shell 3.

There are three p orbitals in the
p subshell.

Dumbbell Shape
These five d orbitals in the d subshell.

Cloverleaf Shape
There are seven f orbitals in the
f subshell.
Theses are the four types of orbitals
Orbital Diagrams and
Electron Configurations
Orbital Diagrams
Orbital Diagrams
Two electrons have
opposite spins in an

Orbital Diagrams
Electron Configurations
Electron Configurations
Here are examples for H and He atoms.

Notice how the filling order on the right is
reflected in the periodic table ( i.e moving left to
right within a row )
Rules for Placing Electrons in Orbitals
Rules for placing electrons in orbital

      1. Maximum of 2e- per orbital

      2. Fill lowest energy orbitals first

      3. Fill empty orbitals first
Practice Exercise Draw an orbital
diagram and the electron configuration
for a lithium atom.

Repeat for C

Repeat for N
Valence Shell and Valence Electrons

Valence Shell: the highest shell number
with electrons.

Valence Electrons: all electrons in the
valence shell.
Classification of the Elements
Elements can be classified by :

(1)Physical Properties ( metal or nonmetal)

(2) Electronic Properties

(s and p block ….. representative elements)
(d block ………. transition elements)
(f block …… inner transition elements)
( p6 block … noble-gas elements)
Elements can be classified by :

(3) Special Names ( alkali (s1 block),
alkaline earth(s2 block),

halogens (p5 block), noble gases (p6 block))
Classification of Elements by
Electronic Properties

                                Fig. 2-16, p. 56
Atomic Radius
Atoms vary in size.

Size is determined by
the atomic radius.
What is the trend
in atomic size going
doing a group?
 Practice Exercise Arrange the elements
in order of decreasing atomic radius.

Al, Ba, Si, Mg
Ionization Energy
 Ionization energy is that
amount of energy needed to
remove a single e- from an

This quantity is used to evaluate
the reactivity of an element.
Plot of Ionization Energy for Selected Elements

 Practice Exercise Arrange the elements
in order of increasing ionization energy.

Cl, Na, K, Al
Another Question about
the Atomic Masses
Why do the atomic masses of the elements
have decimal places?
The atomic masses are weighted averages of
an element’s isotopes.

Recall isotopes are atoms with the same
atomic number (i.e. same #protons) but
different atomic mass ( i.e. different #neutrons) .
Exam I Review Questions
Which element has this configuration?

   1s2 2s2 2p6 3s2 3p6 4s2 3d2
How are the elements in set A different
from those in set B.

  Set A                        Set B
 Cl, H, P , Si             Zn, Al, Ba, Mg
Which set of elements consist of a metal
and a nonmetal>

 a. Zn and Ga

 b. S and Cl

 c. F and I

 d. P and Bi
 Specific Heat Problem
Determine the heat energy in calories
needed to increase the temp. of 20.0 g of olive
oil from 25.0º C to 55.0ºC.
Sp. heat = Q / m x ΔT

Q is heat absorbed, m is mass, and
T is temperature.
This is the answer to Problem 2.72c
Specific Heat Problem
Determine the specific heat of a substance
that requires 18.6 cal of heat to change 12.0 g
of the substance by 10.0 ºC.
This is the answer to Problem 2.69
 Temperature (Problem 2.64)

What is the temp. in Fahrenheit of a hypothermia
victim whose body temperature has dropped
to 29.1 ºC
 Celsius and Fahrenheit Formula Scales

C = 5/9(F -32)
and F = 9/5C + 32

Answer to problem on previous slide is
84.4 F ( round 84.38 to 84.4)
Density (Problem 2.55)

How many mL is 20.0 g of acetone?
The density of acetone is 0.791 g/mL
The atomic number of an oxygen isotope
containing 10 neutrons is

 a. 20

 b. 10

 c. 8

 d. 18

                       Correct answer is c.
Classify the following as a compound,
element, or neither.



3. N3¯


5. H3O+
            1.cmpd, 2. element, 3.neither, 4.cmpd, 5. neither
Discuss the principal difference between matter
and energy using an example of each.

Compare the characteristics of a proton and a

 The charge on all compounds is

Write the electron configuration for arsenic(As).
Draw an orbital box diagram for a boron atom.
Which element is not a halogen?

a. chlorine

b. bromine

c. iodine

d. radon

                          Correct answer is d
Which element is not a metal?

a. zinc

b. lithium

c. hydrogen

d. barium
Which element has the largest ionization energy?

a. P

b. K

c. Ar

d. F
Which element has the largest atomic radius ?

a. P

b. K

c. Ar

d. F
The element gold (Au) is located in the
_________subshell region of the periodic table.

a. s area

b. p area

c. d area

d. f area
The element gold (Au) is located in the
_________subshell region of the periodic table.

a. s area

b. p area

c. d area

d. f area
The element gold (Au) is located in the
_________subshell region of the periodic table.

a. s area

b. p area

c. d area

d. f area
The element gold (Au) is located in the
_________subshell region of the periodic table.

a. s area

b. p area

c. d area

d. f area
A fluorine atom has ______ unpaired electrons
in its 2p subshell..

a. 0

b. 1

c. 2

d. 3
                           Correct answer is b
What is the difference between a molecule and
an atom? Give examples of each.
True or False All matter can be classified as
either energy or a pure substance.

Why is this true or why is it false?
What is difference between a chlorine-35 isotope
and a chlorine-37 isotope.

Chlorine-37 has two more neutrons than chlorine-35.
When butter becomes rancid this is best
classified as a ……...

a. physical change
b. chemical change

Explain why this is either a physical change or
chemical change.
How many grams is a 3.55 lb bag of sugar?
Complete the following conversions:

0.000789 cm = ? m

5.50 x 105 mL = ? L
Which metal is a transition metal?

a. Sn
b. Pb
c. Hg
d. Al

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