Transcript I. Structure of the Atom

Ch. 4 - Atomic Structure
I. Structure of the Atom
 Dalton’s Atomic Theory
 Subatomic Particles
A. Dalton’s Atomic Theory
 Every element is made of tiny,
unique, particles called atoms that
cannot be subdivided.
 Atoms of the same element are
exactly alike.
 Atoms of different elements can
join to form molecules.
B. Subatomic Particles
ATOM
ATOM
NUCLEUS
NUCLEUS
ELECTRONS
ELECTRONS
PROTONS
PROTONS
NEUTRONS
NEUTRONS
POSITIVE
CHARGE
NEUTRAL
CHARGE
Most of the atom’s mass.
NEGATIVE
CHARGE
NEGATIVE CHARGE
in a neutral atom
Atomic Number
equals the # of...
B. Subatomic Particles
B. Subatomic Particles
Atoms have no
overall charge
because the
protons (+)
cancel out the
electrons (-).
Neon
10 protons = +10
10 neutrons = 0
10 electrons = -10
total charge 0
Ch. 4 - Atomic Structure
II. Electron Cloud Model
 Orbital
 Energy Levels
 Bohr Model Diagrams
B. Energy Levels
 Electrons can only exist at
certain energy levels.
 Low energy levels are
close to the nucleus.
 Each energy level (n) can
hold a certain number of
electrons.
A. Orbital
 Region where there is 90% probability of
finding an electron.
 Can’t pinpoint the
location of an
electron.
 Density of dots
represents the
probability.
C. Bohr Model Diagrams
 Simplified energy levels using Bohr’s
idea of circular orbits.
Lithium
Atomic #: 3
Mass:
7
# of p:
# of e:
# of n:
3
3
4
een np n
pn p
e-
Can replace with:
3p
4n
Maximum eLevel 1
Level 2
Level 3
Level 4
2e8e18e32e-
C. Bohr Model Activity
 Choose a number between 1 & 18.
 Find your element by the atomic number you picked.
 Draw a Bohr Model diagram for your element on
your marker board.
• Round off the atomic mass listed on the table and
subtract the atomic # to find the # of neutrons.
• Abbreviate the # of ‘p’ and ‘n’ in the nucleus.
 Have a partner check your drawing.
 Repeat with a new element.
Ch. 4 - Atomic Structure
III. Masses of Atoms
 Atomic Mass
 Mass Number
 Isotopes
A. Atomic Mass
 atomic mass unit (amu) – unit of
measurement
 Average atomic mass – the average mass
of all the isotopes of the atom.
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B. Mass Number
 Sum of the protons
and neutrons in the
nucleus of an atom.
 Always a whole
number.
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 # of neutrons = mass # - atomic #
C. Isotopes
 Atoms of the same element with
different numbers of neutrons.
 Isotope symbol:
Mass #
Atomic #
“Carbon-12”
12
6
C
C. Isotopes
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