Atomic Structure and the
Periodic Table
Early Models of the Atom
Dalton’s Atomic Theory
- All elements are composed of atoms
- All atoms of a given element are identical
- Atoms of different elements are different
- Compounds consist of the atoms of different
elements
- Atoms are not created or destroyed in a
chemical change
Structure of the Nuclear Atom
Thomson’s experiment- showed that atoms
contained electrons
Thomson’s Cathode Ray Tube
Plum Pudding Model
Structure of the Nuclear Atom

Electron- negatively charged subatomic
particle

Proton- positively charged subatomic particle
found in the nucleus of the atom

Neutron- a subatomic particle with no charge
that is found in the nucleus
Atomic Structure
Structure of the Nuclear Atom

Rutherford’s Experiment- showed that atoms
have a dense nucleus
Rutherford’s Model
Atomic Structure
Nucleus –
• very dense (contains nearly all the mass
of the atom yet occupies a very small
space)
• location of positively charged protons
and neutral neutrons
Electron Cloud –
• space surrounding the nucleus
• location of negatively charged electrons
Subatomic Particles
Subatomic
Particle
Location
Charge
Mass
Proton
Nucleus
+
Yes
Neutron
Nucleus
0
Yes
Electron
Electron
Cloud
–
No
Bohr Model of the
Atom

Determined that electrons orbit the
nucleus in specific energy levels
Electron Level
1
2
3
4
Electrons in Level
2
8
18
32
Bohr Model
The # of protons = atomic number
•The number of protons determines the
element. All atoms of the same element
have the same # of protons.
• Count the protons and use the
atomic number on the periodic
table to identify the element.
The # of protons = atomic number
Identify the element…
7 protons, so…
Distinguishing Between Atoms
Practice- How many protons and electrons are in
each atom?
a.
Fluorine
b.
Aluminum
c.
calcium
Mass number = # of protons + # of neutrons
Find the mass number…
So the mass number is…
Distinguishing Between Atoms
Practice- How many protons, electrons and
neutrons are in the following atoms?
Atomic Number
Mass Number
a.
Beryllium
4
9
b.
Neon
10
20
c.
Sodium
11
23
Mass number – atomic number = neutrons
Practice- How many neutrons are in each atom?
16 O
a.
8
108 Ag
b.
47
207 Pb
c.
82
1. Use the information below to answer the
questions that follow.
A certain element has a nucleus containing
eight protons and ten neutrons and has ten
electrons orbiting the nucleus.
a. What is the name of this element?
Oxygen
b. What is the mass number of this element?
18
Distinguishing Between Atoms

Isotopes- atoms with the same number
of protons but different number of
neutrons
Protons + Neutron = Atomic Mass
If the number of protons never
changes than it’s the number of
neutrons!!!
2. The picture
shows a model of
the element –
a. Fluorine
b. Carbon
c. Beryllium
d. Oxygen
3. Label each part of the diagram above.
W – Nucleus
X – Neutron
Y – Proton
Z – Electron
Distinguishing Between Atoms

Atomic mass- the weighted average of the
masses of the isotopes of an element
- Atomic mass unit- a unit of mass equal to
one-twelfth the mass of carbon twelve atom
Practice- The three isotopes of chromium are
chromium-50, chromium-52, and chromium
53. How many neutrons are in each isotope,
given that chromium always has an atomic
number of 24?
Calculating average atomic mass
Average atomic mass = (fractional abundance of
isotope 1)(mass of isotope 1) + (fractional
abundance of isotope 2)(mass of isotope 2)
Practice 1. Calculate the atomic mass of
bromine. The two isotopes of bromine have
atomic masses and relative abundances of
78.92 amu (50.69%) and 80.92 (49.31%)
Practice 2- Element X has two natural isotopes. The
isotope with a mass of 10.012 has a relative
abundance of 19.91%. The isotope with a mass of
11.009 has a relative abundance of 80.09%. Calculate
the atomic mass of this element.
Practice 3- Calculate the percent abundance of copper63 if the atomic mass is 63.546 and the exact masses
of the isotopes are 64.93 amu and 62.93 amu.
The Periodic Table

Mendeleev- arranged the elements by
increasing atomic mass
The Modern Periodic Table- shows
all the known elements in order of
increasing atomic number
Group –elements located in the same column.
Period – elements in the same row.
The periodic table is organized to
group elements with similar
properties in vertical columns
Iodine
• gain electrons to become negative ions
Sulfur
• dull
• brittle
• poor conductors of heat and electricity
• usually gases at room temperature
• lose electrons to become positive ions
• shiny
• malleable
• ductile
• good conductors of heat and electricity
• usually solids at room temperature
Right
On
the
staircase
Leftofofthe
thestaircase
staircase
The Modern Periodic Table
Metals- elements on the left side of the table
- alkali metals- metals in group 1A
- alkaline earth metals- metals in group 2A
- transition and inner transition metals- group B, located in the
center of the table
Metalloids- have properties intermediate to metals and nonmetals

Nonmetals- elements on the right side of the table
- halogens- nonmetals in group 7A
- noble gases- elements in group 0
Natural States of the Elements
Diatomic Elements
BrINClHOF Elements- diatomic
The Modern Periodic Table

Periods- horizontal rows on the periodic table

Periodic law- when elements are arranged by
increasing atomic number, there are periodic or
repeating properties

Groups (families)- columns on the periodic table
- Group A elements- representative elements
- Group B elements- transition metals
1. Which of the following groups contains
members with similar chemical activity?
a. Li, Be, C
b. Be, Mg, Sr
c. Sc, Y, Zr
d. C, N, O
3. Which of the following elements is
rarely involved in bonding because
it is already stable?
a. Ca
b. O
c. Ar
d. Cl
4. Elements in Group 16 of the
periodic table usually –
a. form large molecules
b. gain electrons when bonding
c. act like metals
d. solidify at room temperature
5. A new element is discovered. It can
be hammered flat into sheets and
made into wire. The element is most
likely –
a. a metal
b. hydrogen
c. a nonmetal
d. a metalloid