Transcript Standards  1a. Students know how to relate the position of an element in the periodic table to its atomic number and atomic.

Standards
 1a. Students know how to relate the position of an
element in the periodic table to its atomic number
and atomic mass.
 1b. Students know how to use the periodic table to
identify metals, semi-metals {metalloids}, nonmetals, and halogens
 1e. Students know the nucleus of the atom is much
smaller than the atom yet contains most of its
mass.
Purpose
 We will use this information to build our chemistry
knowledge.
 We will use this information as the foundation to
calculate limiting reagent problems.
 The standardized exams in the spring will test you on
this information.
Objectives
 Know the 3 particles of the atom and where they
reside
 Know the difference between atomic number and
mass number
 Know how to write nuclide symbols
 Know the three isotopes of hydrogen
 Know how to calculate atomic mass
 Know how to calculate percent abundance
First Some Questions…
 What are atoms made up of?
 Protons, Neutrons and Electrons
 Where do you find these particles?
 Protons and Neutrons are located in the nucleus
 Electrons are located in the outer rings, outside the
nucleus.
Vocabulary
 Atom- from the Greek atomos=indivisible. The atom is the
smallest particle of an element that retains the properties
of that element.
 Nucleus: the center of the atom; composed of neutrons
and protons. Because the mass of the proton and the
neutron is much larger than that of electrons, almost all
the mass is located in the nucleus.
 Ion: a charged particle; # protons ≠ # electrons
 Electrons occupy most of the volume of an atom
outside/around the nucleus.
Fundamental Particles
 Proton
 A positively charged particle located in the nucleus.
 Neutron
 A neutral particle located in the nucleus.
 Electron
 A negatively charged particle located outside the
nucleus.
The Atom
Animation of the Atom
 http://vvsd.schoolwires.net/2349201028132033980/lib/
2349201028132033980/atom_animated.gif
 http://vvsd.schoolwires.net/2349201028132033980/lib/
2349201028132033980/atom_animated.gif
http://www.google.com/imgres?imgurl=http://members
.shaw.ca/len92/atom_animated.gif&imgrefurl=http://me
mbers.shaw.ca/vict/electricity_intro.htm&h=260&w=270
&sz=6&tbnid=tAjDJsPzhGAxvM:&tbnh=95&tbnw=99&z
oom=1&usg=__8fyNMhCgDiqyFH3eSESGT0PZS2o=&do
cid=gQA81nwMuwx71M&sa=X&ei=ElBlUpyKFYP_igLhlI
GwBg&ved=0CDgQ9QEwBA
Question
 What differentiates one atom from another atom?
 The number of PROTONS
Atomic Number (Z)
A
Z
El
 Number of protons in the nucleus of an atom
 This number is found on the Periodic Table
 Atomic Number identifies an element
 Always a positive number (b/c it is a counting
#)
 Tells number of electrons in a neutral atom
 An atom is electrically neutral
What does it mean to be
electrically neutral?
 The atom has no charge
 The number of protons = the number of electrons
Question
 What observations can you make about atomic
numbers on the periodic table?
 Atomic Number increases as you go across the rows from
left to right.
Questions
 What is the atomic number of Chlorine?
 What can you tell me about its protons and electrons?
 What element has 20 protons?
 What is the relationship between the # protons and
the atomic number?
 They’re equal.
Complete the Chart
Element
Symbol
Atomic #
# Protons
Potassium
K
19
19
Boron
B
5
5
Sulfur
S
16
16
Yttrium
Y
39
39
Atomic Structure of Potassium
Mass Number (A)
A
Z
El
 Total number of protons and neutrons in the
nucleus of an atom
 Always a positive number
 You can determine the nuclear composition
of an atom from its mass number and atomic
number
Question
 What do the atomic number and the mass number
have in common?
 Both Positive integers
 Both have the same # of protons
How to find # of Neutrons
 Mass # - Atomic#= # Neutrons
 Or
 # protons + # neutrons= Mass #
 (atomic number + # neutrons)=Mass #
Complete the Chart
Atomic#
Mass#
#Protons
#Neutrons #Electrons Chemical
Symbol
9
19
9
10
9
F
14
29
14
15
14
Si
22
47
22
25
22
Ti
25
55
25
30
25
Mn
6
12
6
6
6
C
Isotopes
 Atoms of the same element with differing numbers of
neutrons
 Atoms with the same atomic number but different
mass number
 Isotopes of an element have different masses
 Chemical properties of different isotopes are virtually
the same
Nuclide Symbol
A
Z
 A=Mass #
 Z= Atomic #
El
Nuclide
 A specific kind of atom
 Specification of an element in terms of its
nuclear composition/structure
 Tells number of protons and number of
neutrons
Chemical
Symbol
C
Nuclide Symbol
13
6
C
# protons
# neutrons
# electrons
6
[6, 7, 8]
6
6
7
6
Complete the Chart
Atomic#
Mass#
#Protons
#Neutrons #Electrons Chemical
Symbol
Nuclide
Symbol
9
19
9
10
9
F
19
9
14
29
14
15
14
Si
29
14
22
47
22
25
22
Ti
47
22
25
55
25
30
25
Mn
55
25
6
12
6
6
6
C
12
6
F
Si
Ti
Mn
C
3 Isotopes of Hydrogen
Isotope
Of
Hydrogen
Protium
Deuterium
Tritium
Nuclide
Symbol
# protons
# neutrons # electrons
H
1
0
1
2
1
H
1
1
1
3
1
H
1
2
1
1
1
Nuclides
 By specifying the nuclear structure, then you call it a
nuclide.
 But if you say Carbon atom, you do not know which
Carbon atom it is, therefore you don’t know how many
neutrons it has
 Example: Brothers and Sisters You are members of the Jones family, but you have not
specified which Jones member you are referring to. If
you say Jimmy Jones, then we know exactly which
member you are referring to. Just like when you say
carbon-13, we know exactly which kind of carbon atom,
the one 7 neutrons in the nucleus.
Write the nuclide name and nuclide symbol
# protons # neutrons # electrons Nuclide
Name
17
20
18
Chlorine-37
Anion
20
20
18
Calcium-40
Cation
92
146
92
Uranium-238
Nuclide
Symbol
37
17
40
20
Cl
Ca
238
92

2
U
Atomic Mass
 A weighted average of the atoms in a naturally
occurring sample of the element.
 Naturally occurring: no matter where you get the
sample from, it will have the same percentages of
isotopes.
Construct a Fruit Basket
 Fruit Type
Weight of Each Piece
2 grapefruit
14 oz
4 apples
10 oz
3 pears
7 oz
1 kiwi
3 oz
 What is the Average Weight?
Fruit Basket
 Average weight=9.2oz
 Each type of fruit makes a different contribution to the
overall weight
 How many pieces of fruit actually weigh 9.2 ounces?
 None!
 What does 9.2 oz mean?
 Fictitious non-existent piece of fruit
Atomic Mass
 If you have a recipe, you could count items to put
in, say 200 chocolate chips, 3 eggs, etc.
 But suppose I have a recipe to make a compound.
 I need 100 hydrogen atoms and 50 oxygen atoms-you
cannot count atoms or pluck them out with atomic
tweezers!
 So instead they are massed.
 Careful here, the mass of an object is completely
different from the weight of an object.
Question
 What accounts for the mass of the atom?
 # protons & # neutrons in the nucleus
Atomic Mass
 Know that 1.0 amu is defined as exactly 1/12
the mass of a 126C atom.
 Carbon-12 has 6 protons and 6 neutrons,
therefore 1 proton or 1 neutron = ~1 amu
 1 amu = 1.6606 x 10 -24 grams
 Since the mass mostly depends on # protons
and # neutrons, you’d think atomic mass
would be a whole number, but it isn’t. How
come?
Atomic Mass
 In nature, most elements exist as a mixture of 2 or more isotopes.
 Each isotope of an element has a fixed, constant mass and fixed constant
relative abundance.
 Relative abundanceThe amount (%) of the isotope present in a sample of the element
 Sample of carbon from anywhere in the world; coal from S. Africa, W.
Virginia or Pennsylvania
→ 99% C-12 and 1% C-13
 Atomic Mass on the periodic table takes into account the larger and
smaller masses of the isotopes
 → Idea of weighted average
Calculating Atomic Mass
 To calculate atomic mass you need to know 3 things:
 # of stable isotopes
 Mass of each isotope
 % abundance of each isotope
Example: Chlorine Calculation
 mass of isotope X relative abundance
+ mass of isotope X relative abundance
=_______amu
Isotope
Mass of Isotope
Relative Abundance
Cl-35
34.969
75.77%
Cl-37
36.935
24.23%
Atomic Mass
 (34.969)(.7577) + (36.935)(.2423) =
35.45 amu
 That’s the same value on the periodic table!
Question
 How many chlorine atoms actually have a mass of
35.45 amu?
 NONE
 So the atomic mass, in amu, is the average of a
fictitious non-existent atom of an element.
Example: Copper Calculation
Isotope
Mass of Isotope
Relative Abundance
Cu-63
62.9298amu
69.09%
Cu-65
64.9278
30.91%
Atomic Mass
(62.9298)(.6909)+(64.9278)(.3091)= 63.5464 amu
Calculating Relative Abundance
 To Calculate % Abundance:
 Make a Chart
 Isotopic Mass x % Abundance of each isotope
 Set-up equation
 Solve for “x”
 Plug in “x” value to solve for “y”
Example
Isotope
Mass of Isotope
B-10
10.013
B-11
11.009
10.013 (x) + 11.009 (1 –x) = 10.811
10.013x + 11.009 -11.009x = 10.811
-0.996x = -0.198
x = .1987
y= 1-.1987
y= .8013
B-10 = 19.87%
B-11 = 80.13%
Relative Abundance
x
1- x
1.00
x + y = 1.00
y=1–x
Atomic Mass
The End