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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
- Atoms are not created or destroyed in a
chemical change
Structure of the Nuclear Atom
Thomson’s experiment- showed that atoms
contained electrons
Plum Pudding Model
Structure of the Nuclear Atom
Electron- negatively charged subatomic
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
Structure of the Nuclear Atom
Rutherford’s Experiment- showed that atoms
have a dense nucleus
Rutherford’s Model
Structure of the Nuclear Atom
Nucleus- contains protons and neutrons.
Electrons orbit the nucleus
Comparing the Parts of the Atom
Bohr Model of the Atom
Determined that electrons orbit the nucleus in
specific energy levels
Electron level
1 2 3 4
Electrons in the level 2 8 18 32
Bohr Model
Distinguishing Between Atoms
Atomic number- number of protons
Practice- How many protons and electrons are in
each atom?
Distinguishing Between Atoms
Mass number- sum of protons and neutrons
Practice- How many protons, electrons and
neutrons are in the following atoms?
Atomic Number
Mass Number
Mass number – atomic number = neutrons
Practice- How many neutrons are in each atom?
16 O
108 Ag
207 Pb
Distinguishing Between Atoms
Isotopes- atoms with the same number of
protons but different number of neutrons
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?
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
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
The periodic table is organized to
group elements with similar
properties in vertical columns
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
Properties of the Metals
1. Conduct heat and electricity
2. Malleable (can be hammered into thin sheets)
3. Ductile (can be pulled into wires)
4. Lustrous (shiny)
Natural States of the Elements
Diatomic Elements
BrINClHOF Elements- diatomic
Elemental Solids
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
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