Download Chapter 5 Atomic Structure and the Periodic Table Section 5.1

Chapter 5
Atomic Structure and the
Periodic Table
Section 5.1
Atoms
Q OBJECTIVES:
–Summarize Dalton’s atomic
theory.
–Describe the size of an atom.
Adapted from notes by Stephen L. Cotton ©
History of the atom
Greek philosopher:
–.
~400 B.C.
Q Smallest possible piece of stuff (matter)?
–.
- not to be cut
Q
Dalton’s Atomic Theory (late 1700s)
1 All matter is made of tiny
particles called atoms.
2 Atoms of the same element are
.
3 Atoms of different elements combine in
to form compounds.
4 Chemical reactions involve the
of atoms… atoms are
neither created or destroyed.
How Small Is an Atom?
of cutting a piece of
aluminum foil into smaller and
smaller pieces… How many times
can it be cut and still be aluminum?
Q An
is the smallest particle of
an element that retains the
properties of that element
Section 5.2
Structure of the Nuclear Atom
Q Think
Q
OBJECTIVES:
– Distinguish among protons, electrons,
and neutrons in terms of relative
mass and charge.
– Describe the structure of an atom,
including the location of the protons,
electrons, and neutrons with respect
to the nucleus.
1
Thomson’s Experiment
Parts of Atoms
Q J.
J. Thomson (1897) - made a
piece of equipment called a
.
–Consists of a
lined
vacuum tube.
-
Thomson’s Experiment
Thomson’s Experiment
Voltage source
Voltage source
-
+
Q By
Other particles
Q.
+
- positively charged pieces
1840 times heavier than the
electron – E. Goldstein
Q.
- no charge but the same
mass as a proton – J. Chadwick
Q Where are these “pieces” in the
atom?
adding an electric field…
Rutherford’s Gold Foil Experiment
Ernest Rutherford - English physicist.
(1910)
Q Alpha particles – helium atoms without
their electrons
Q Shot alpha particles at a very thin piece
of
.
Q
2
What did Rutherford Expect?
Q The
alpha particles would pass
through the atom
changing
direction very much.
Q Thought the negative charges were
spread out evenly in the atom and
that most of the alpha particles
right through the gold
would
foil.
What he expected
Since he thought the
mass was evenly
distributed in the atom
Because
What he got
3
How he explained it
Atom is mostly
Q Small, dense,
positive piece
at center =
Q Alpha particles
are deflected
if they get close
enough to the
Q
.
+
+
Subatomic particles – p.111
Relative Actual
mass (g)
Name Symbol Charge mass
Electron
Proton
Neutron
Counting the Pieces
= number of
protons in the nucleus
Q.
determines which atom
you have.
Q Atomic number is the same as the
in a neutral atom.
Q.
= the number of
protons + neutrons.
Section 5.3
Distinguishing Between Atoms
Q
OBJECTIVES:
– Explain how the atomic number identifies an
element.
– Use the atomic number and mass number of an
element to find the numbers of protons, electrons,
and neutrons.
– Explain how isotopes differ, and why the atomic
masses of elements are not whole numbers.
– Calculate the average atomic mass of an element
from isotope data.
Symbols
Q.
X
Z
A
Note: The arrangement of X, Z, and A may vary!!!
4
Symbols
the:
–number of protons
–number of
neutrons
–number of
electrons
–atomic number
–mass number
Symbols
Q Determine
Q Determine
F199
the:
–number of protons
–number of neutrons
–number of electrons
–atomic number
–mass number
Symbols
Q If
an element has an atomic
number of 34 and a mass number
of 78 what is the:
–number of protons
–number of neutrons
–number of electrons
–complete symbol
Isotopes
Dalton was wrong… atoms of the same
element are
always identical!!!
Q.
.
– Have
number of protons so are
same element, but
number
of neutrons, so are isotopes of the
same element… Ex: C-12 & C-13.
Q
80
35
Br
Symbols
Q If
an element has 91 protons and
140 neutrons what is the:
–atomic number
–mass number
–number of electrons
–complete symbol
Measuring Atomic Mass
Q Unit
is the
Q 1 amu =
the mass of a C-12
atom… which happens to have
protons and
neutrons in its
nucleus!!!
5
Average Atomic Mass
Q Calculate
the average atomic mass of
copper if copper has two isotopes.
69.1% of the isotopes have a mass of
62.93 amu and 30.9% of the isotopes
have a mass of 64.93 amu.
Atomic Mass
Q Magnesium
has three isotopes.
78.99% magnesium-24 with a mass of
23.9850 amu, 10.00% magnesium-25
with a mass of 24.9858 amu, and the
rest is magnesium-26 with a mass of
25.9826 amu. What is the average
atomic mass of magnesium?
Average Atomic Mass
not usually a whole number
because it is an
.
Q Is the number with the decimal
places for each element in the
periodic table usually printed above
or below the element symbol… we
will use average atomic mass a lot
in the future!!!
Section 5.4
The Periodic Table: Organizing
the Elements
Q Is
Development of the Periodic
Table
Q mid-1800s,
about
elements known
by
Q Elements arranged in order of
increasing
Q Father of the first “
”
Q Developed
Q OBJECTIVES:
–Describe the origin of the periodic
table.
–Identify the position of groups,
periods, and various other
locations in the periodic table.
Mendeleev
Left blanks spaces for undiscovered
elements based upon “
”
Q Examples of periodic Trends
–
–
–
–
Q Ex: Mendeleev predicted Ekasilicon
existed, which was later discovered and
named
.
Q
6
Modern Day Periodic Table
Q Henry
Moseley – arranged
elements according to increasing
.
Q Developed the
Periodic
Table.
Periodic table
Q Horizontal
Q Vertical
column =
Areas of the periodic table
Q Group
A elements = .
rows =
Metals
Q
Generally:
Group IA –
Group 2A –
Q Group B Q
Q
Nonmetals
Q Generally:
and .
Metalloids
Q Have
properties intermediate
between
.
Q Located along the “
” of the
periodic table.
Q Group
7A –
Q Group 0 –
7