Name: ____________________________
Date: ______ Per: _______
Properties and Interactions of Matter:
Advances in Atomic Theory
Democritus (400 B.C.) - was the first person to use
the term “atoms” to describe the tiny units of
matter that make up all things.
ATOM  Derived from the Greek word “atomos”
meaning unable to cut
 Smallest part of an element
1. Ancient Greek Model of the Atom
Aristotle proposed the existence of the four
elements:
Earth, Air, Fire, Water. All matter was a
combination of those elements.
(Draw Ancient Greek model of the four elements)
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2. Thompson’s Plum Pudding Model of
the Atom
John Dalton (1803) English chemist who
developed the first atomic theory of atoms based
on laboratory experiments.
J.J. Thompson (1897) English physicist who
discovered a negatively charged subatomic
particle.
Thompson named this particle the ELECTRON.
(Draw Plum Pudding Model of the Atom)
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3. Rutherford’s Positive Nucleus
Model of the Atom
Ernest Rutherford (1911) - Gold foil experiment
showed that atoms have a small but heavy center
called the NUCLEUS.
The nucleus contains positively (+) charged
PROTONS and neutrally charged NEUTRONS.
(Draw Positive Nucleus Model of the Atom)
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4. Bohr’s Electron Shell Model of
the Atom
Neils Bohr (1913) - Danish physicist who
determined that electrons orbit the nucleus in welldefined orbits called electron shells.
( Draw Electron Shell Model of the Atom)
Draw for Carbon
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5. Electron Cloud Model of the Atom
Electron Cloud Model (1926) - electrons move
about around the nucleus in a region called an
electron cloud. It describes the region where an
electron is most likely to be.
(Draw Electron Cloud Model of the Atom)
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Properties and Interactions of Matter:
Parts of an Atom
An atom consists of two parts:
1) Nucleus – positively (+) charged center that has
 protons - (+) charge
 neutrons - no charge
(Mass of protons and neutrons is equal)
2) Electron Cloud - surrounds nucleus
 electrons – negative (-) charge
Electron Cloud Model
Each region (energy level) can hold a specific number of
electrons before it becomes filled
Energy Levels
1 (lowest energy)
2
3
4
Max # of Electrons
2
8
18
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Atomic Number
The number of protons in the nucleus
(In an electrically neutral atom, the number of protons also equals
the number of electrons)
* It is the number of PROTONS in the nucleus that determines the
element. All elements of the same type have the same number of
PROTONS in the nucleus.
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Masses of the Atoms
Mass of proton or neutron is about 2000 times the mass of an
electron. Most of the mass of an atom is a result of the protons and
neutrons.
Atomic Mass
Atomic mass is measured in Atomic Mass Units (AMU’s)
One AMU is equal to one-twelfth the mass of a carbon atom
containing six protons and six neutrons
Mass Number
The sum of the number of protons and the number of neutrons
in the nucleus of an atom
Ex. Sodium, Na
11 P
12 N
23 Mass #
Lead, Pb
82 P
125 N
207 Mass #
Given the table below, fill in the missing information.
ELEMENT
AT. #
# PROT.
# NEUT.
Boron
Carbon
Oxygen
Sodium
Copper
Iron
Sulfer
5
6
5
6
6
8
12
8
11
29
26
29
# ELEC.
6
8
11
29
MASS #
11
12
23
63
56
32
AT. MASS
10.81
12.01
15.99
22.99
63.55
55.85
32.07
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Atoms of a particular element must always have the same number of
protons but the number of neutrons may vary.
Isotopes - Atoms of the same element that have different numbers
of neutrons.
Isotopes can be written two ways:
1. The name of the element followed by the mass number.
Ex. Carbon - 12
2. The chemical symbol with the mass number as a superscript
Ex. 12C
Given the isotopes listed below, enter the correct number of protons,
neutrons, and electrons for each.
Hydrogen - 1 or 1H
#P =
#N =
#E =
Hydrogen - 2 or
#P=
#N=
#E=
Hydrogen - 3 or
2
H
3
H
#P =
#N =
#E =
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The Periodic Table
The Periodic Table arranges elements according to repeated changes in properties
Arrangements of Elements on the Periodic Table
Periods: Horizontal rows of elements
 The period an element is in is equal to the number of energy levels it has.
(see the column of numbers in the upper right hand corner of each box)
 Properties change slowly from one end of each row to the other.
Groups: Vertical columns of elements
 All elements in a group have similar properties because they have similar electron
arrangements.
 It is the number of electrons in the outer energy level that determines the properties
of an element.
Types of Elements on the Periodic Table
Metals: metallic properties increase as we go to the left side of the periodic table
 most metals are solid at room temperature
 most metals have a shiny luster
 most metals are good conductors of electricity
 metals have 1 to 3 electrons in their valence (outer) orbit
Non-metals: Non-metallic properties increase as we go to the right on the periodic table
 most non-metals are gases at room temperature, while some are brittle solids
 non-metals are poor conductors of electricity
 non-metals have 5 to 8 electrons in their valence (outer) orbit
Metalloids: Metalloids are located at the boundary of the metals and non-metals
 metalloids have properties of both metals and non-metals
Transition Elements: Elements located in groups 3 through 13
 Considered metals, but have properties not found in elements of other groups
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