Transcript Chapter 5 Atomic Theory

Early Atomic Theory and Structure
Chapter 5.1 Early Thoughts
o Roots of atomic
theory are as old as
440 B.C. with
Democritus’ idea of
the atom
o It took 2 000 years
for us to expand on
this idea. The new
theory was to be
done by an English
schoolmaster John
Dalton in the early
1800s.
Dalton’s Atomic Theory
o
o
o
o
His theory included 6 postulates
1. Elements are made up of atoms
2. Atoms of the same element are alike
3. Atoms of different elements are different by
virtue of their size and mass
o 4. Chemical compounds are formed by the
union of two or more atoms of different
elements
o 5. Atoms combine to form compounds in
whole number ratios (1:2 or 2:2, etc]
o 6. Atoms of two elements may combine in
different ratios to form more than one
compound
5.4 - 5.8 Subatomic Particles
o Through the years of the late 1800s and
into the early 1900s it was determined
that there are three subatomic particles
o Electrons (discovered first)
o Protons (reasoned to exist if elements are
neutral)
o Neutrons (discovered last)
Electrons
o Occupies the area outside the
nucleus
o Negative charge,
o Relative to the other
subatomic particles it has
negligible (so small that it can
be ignored) mass.
Protons
o Occupies area in the nucleus,
o Positive charge
o Mass roughly equal to
neutrons
Neutron
o Occupies Nucleus
o No charge
o Roughly the same mass as the
proton
Answers of the Day
Particle
Charge
Location Relative
(in/out
Mass
side
(0 or 1)
nucleus)
Inside
1
nucleus
Proton
positive
Electron
negative outside
nucleus
0
Neutron
neutral
1
inside
nucleus
Atomic Number
oAtomic Number = the
number of protons; unique to
each element and the order
of the periodic table is
arranged
Mass number
oMass Number = protons +
neutrons (whole number)
oCannot be found on the
periodic table!
Charge = # protons - # electrons
CHARGE
Self Check
o What is the charge of a
substance with 14 protons, 15
neutrons, and 14 electrons?
o
Now let’s begin the grid
.
Check yourself
o The nucleus is made up of what
two types of subatomic
particles?
Same element different mass
ISOTOPES
Isotopes
oIsotopes have same
number of protons (so
they are the same
element) but different
number of neutrons
oSome isotopes are
radioactive
ISOTOPIC NOTATION
isotopes are atoms with the same number of protons
but different number of neutrons
A
Z
X
A = mass number
(the total number of protons +
neutrons)
Z = atomic number
(the total number of protons)
X = element symbol
READING ISOTOPIC NOTATION
46
21
Sc
46 = mass number
(the total number of protons (21) +
neutrons (25)
21 = atomic number
(the total number of protons (21)
Sc = element symbol In a neutral atom,
the number of electrons (21) is equal to the
number of protons.
PRACTICE PROBLEMS
15N
7
# protons = ____
___
35P
15
# p = ____
62Cu2+
29
# p = ____
76Se3-
34
# p = ____
8
# neutrons= ____
#electrons = 7
# n=20
____
15
#e- = ___
33
# n= ____
27
#e- = ___
42
# n= ____
#e- =37
___
Formulas you should know
o Atomic number = # of protons
o In an atom (uncharged):
o # of protons = # of electrons
o Mass # = # protons + # neutrons or
o # neutrons = mass # - # protons
o Charge = # protons - # electrons (for
ions)
o Remember the atomic # and # of
protons give the element its identity
and does not change
Test your Knowledge
Name
Symbol
Atomic
#
# of
protons
neon
# of
neutrons
Mass #
11
Pb
207
74
110
88
226
8
carbon
F
19
79
118
# of
electrons
Test your Knowledge
Name
Symbol
Atomic
#
# of
protons
# of
neutrons
Mass #
# of
electron
s
neon
Ne
10
10
11
21
10
lead
Pb
82
82
125
207
82
tungsten
W
74
74
110
184
74
radium
Ra
88
88
138
226
88
carbon
C
6
6
8
14
6
fluorine
F
9
9
10
19
9
gold
Au
79
79
118
197
79
Elements composed of atoms
Elements or atoms in
an unbonded state
have the same
number of electrons
as protons
(They are neutral)
Ions
Ions have an unequal
number of electrons and
protons. An atom loses or
gains electrons to take on
a charge (protons/neutrons
are not transferred)
Charge = #protons - #
electrons
Ionic Notation
3X
This means that this
element has a -3
charge.
Self Checker
o If a substance has a charge of
+2, this means that the number of
protons is (circle one: LESS than
or GREATER than) the number of
electrons?
Writing ISOTOPIC NOTATION
1. Write the symbol for the atom with an atomic
number of 21 and a mass number of 48.
48
Sc
2. Give the complete chemical notation for the
nuclide with 23 protons, 26 neutrons and 20
electrons.
49V3+
3. Write the isotopic notation for
110Pd
a. Z = 46
A = 110
b. An atom containing 24 protons, 28
neutrons, and 21 electrons 52Cr3+
c. Titanium-50 50Ti
PRACTICE PROBLEMS
1. 196 Pt4+
118
78 # n = _____
# p = _____
196
mass number = ________
195.1 amu
atomic mass = ________
78
#e- = _____
78
atomic number = _______
platinum
name of element = _______
2. Indicate the appropriate mass number of an element with
30 protons, 30 neutrons, and 28 electrons.
196
Atomic Mass
oAtomic Mass = number on
the periodic table reflecting
the mass all isotopes known
and their relative
percentages (on periodic
table below element’s
symbol--usually not a whole
number)
Atomic Mass
o The atomic mass of an element represents
the average mass of all the isotopes found in
nature. No element exists with only one
possible isotope. Hydrogen has the smallest
number of isotopes: 1H protium, 2H
deuterium, 3H tritium. Its atomic mass is
1.0079 amu (atomic mass units). The atomic
mass is calculated by adding the % of 1H
mass found in nature to the % of 2H mass
found in nature plus the % of 3H mass.
o % 1H + % 2H + % 3H = average mass (atomic
mass)
o Generally the formula used is:
% X + % Y + % Z… = atomic mass.
An instrument called the mass spectrometer is
generally used to determine the percentages
and individual masses of each isotope.
Atomic Mass
o Silver is found to have two stable isotopes, one has an
atomic mass of 106.904 amu and the other weighs
108.905 amu. The first isotope represents 51.82 % of the
mass of the element and the second represents 48.18
%. What is the atomic mass of the element silver?
The equation to use is
%X (mass X) + % Y (mass Y) = average
And remember to turn your percents into fractions before
multiplying.
(0.5182) 106.904 amu + (0.4818) 108.905 amu =?
55.398 amu + 52.470 amu =?
107.868 amu !!
Now look at the periodic table to verify the answer.
PRACTICE PROBLEMS # 8
1. A sample of neon contains three isotopes, neon-20 (with an
isotopic mass of 19.9924 amu), neon-21 (20.9939 amu) and
neon-22 (21.9914 amu). The natural abundances of these
isotopes are 90.92%, 0.257 %, and 8.82 %. Calculate the
atomic weight of neon.
20.17 amu
2. There are only two naturally occuring isotopes of copper,
63Cu and 65Cu. Copper has an atomic mass of 63.55 amu.
What is the natural abundance of each isotope?
65Cu
= 30% & 63Cu = 70%
3. There are only two naturally occuring isotopes of gallium,
69Ga and 71Ga. What is the natural abundance of each
isotope?
69Ga
= 60% and 71Ga = 40%
GROUP STUDY PROBLEM #8
_______1. The element with atomic number 53 contains
a) 53 neutrons b) 53 protons C) 26 neutrons & 27 protons d) 26 protons & 27
neutrons
_______2. The mass of one atom of an isotope is 9.746 x 10-23 g. One atomic mass unit has
the mass of 1.6606 x 10-24 g. The atomic mass of this isotope is
a) 5.870 amu
b) 16.18 amu
c) 58.69 amu
d) 1.627 amu
108
_______3. The number of neutrons in an atom of
a) 47
b) 108
c) 155
47
Ag is
d) 61
27
Al3+
_______4. The number of electrons in an ion of 13
is
a) 13
b) 10
c) 27
d) 14
_______5. What is the relative atomic mass of boron if two stable isotopes of boron have the
following mass and abundance:
10.0129 amu (19.91%) & 11.0129 (80.09%)
a) 10.81 amu
b) 10.21 amu
c) 10.62 amu
d) 10.51 amu
Table Information
Hydrogen
H
Atomic Number
1
Atomic Weight
1.00794
Oxidation States
+1, -1
Electronegativity, Pauling 2.2
State at RT
Gas, Non-metal
Melting Point, K
14.01
Boiling Point, K
20.28
Symbol
The Periodic Table
o Horizontal rows are called
periods
o Vertical columns are called
groups
o We will use 1- 18 as group
designations.
o Group 1 is Alkali Metals
o Group 2 is the Alkaline Earth
Metals
o Group 18 Inert or Noble Gases
o Group 17 Halogens
Larger Groups
o Groups 3 –12 are the heavy
metals or transition elements
o Two periods at the bottom are
called the rare earth elements or
the inner transition elements.
Comparing Regions of the
Periodic Table
Property
Metals
Metalloids
Nonmetals
Physical State at
room
temperature
Mostly Solids
(liquid Hg)
ALL Solids
Some Gases
Some Solids
One Liquid (Br)
Melting Point
Very High
Intermediate
Very Low
Conductivity
Very Good
Conductors
Semi-conductors
Poor conductors
(Good insulators)
Magnetism
Good
Intermediate
Poor