Download 1 Unit 3 Notepack – Atomic Structure Unit 3 Objectives: 1. Describe

Name __________________________
Unit 3 Notepack – Atomic Structure
Unit 3 Objectives:
1. Describe the structure of the atom including: protons, electrons, and neutrons.
2. Explain why isotopes differ.
3. Diagram the Bohr Model of an atom.
Objective 1: Describe the structure of the atom including: protons, electrons, and neutrons.
Atoms and Atomic Theory
•
Atoms – the smallest _______________ of a given type of _______________.
•
Atomic Theory – the idea that _______________ is made up of fundamental particles called
_______________.
Early Ideas About Matter
Democritus
– 400 B.C.
– atomos –
Lavoisier
 Law of conservation of matter- When a chemical reaction occurs, matter is neither
nor
, but only changed.
John Dalton – Father of the Modern Atom
•
Dalton’s Atomic Theory.
1.) All matter is made of
.
2.) All atoms are
and cannot be divided into smaller particles.
3.) All atoms of one element are
, but they are different from all other
elements.
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Subatomic Particles
•
Electrons
•
Protons
•
Neutrons
Diagram:
Electrons
•
J.J. Thomson – Discovered the electron using a
•
Symbol:
•
Mass = 1/1837 amu
•
1 amu ~ the mass of a hydrogen atom
•
Charge = (-1)
ray tube.
Protons
•
Symbol:
•
Mass = 1 amu
•
Charge = (+1)
Thomson’s Model
•
Thomson put both the electron and proton together and proposed the “
” model of the atom.
Diagram the Plum Pudding Model:
Neutrons
•
Symbol:
•
Mass = 1 amu
•
__________ charge
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Nucleus
•
Discovered by Ernest Rutherford.
•
Using the “Gold Foil” experiment, Rutherford determined:
– An atom is mostly
.
– There is a
– The
•
in the middle of the atom containing the protons.
orbit a large distance away from the nucleus.
Proposed the nuclear model of the atom.
Atomic Number
•
Designates the number of
•
Each element has a characteristic
•
The number of electrons
in a
of an atom.
.
the atomic number in a neutral atom.
Mass Number
•
Designates the total number of
and
in an atom.
•
Number of neutrons =
-
•
Atoms of the same element can have different mass numbers.
Objective 2: Explain why isotopes differ.
Isotopes
•
Atoms with the same number of
•
Isotopes of an element have the same
•
Nuclear Symbol or isotopic symbol – shows
, but different numbers of
.
number, but different mass numbers.
of protons, neutrons and
electrons in an atom.
•
Isotopes may also be described by labeling the name following by the
number. (Example: carbon-12)
Diagram the nuclear symbol for lithium – 7, Helium – 4, Titanium – 48:
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Atomic Mass
•
Weighted
mass of the atoms in naturally occurring sample of an element.
•
Masses are based off of the atomic mass unit (amu) defined as one
the
mass of a carbon-12 atom.
Atomic Mass Example
•
In nature carbon is composed of 98.89% 12C atoms and 1.11% 13C atoms. 12C has a mass of
12 amu and 13C has a mass of 13.0034 amu. What is the average atomic mass of carbon?
Objective 3: Diagram the Bohr Model of the atom.
Bohr Model
•
Niels Bohr (1913) – Bohr Model stating
travel around
in energy levels.
•
Uses
to show the energy levels.
•
The number of rings should match the
the element is in on the periodic table.
Bohr Model Diagram
•
The
in the nucleus = the
.
•
The
in the nucleus = the mass number - the atomic number.
•
Electrons = number of protons. Fill the shells from
to
until
the correct number of electrons are added.
•
This model works for the first
Diagram Lithium-7
.
Diagram Aluminum-27
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Diagram Nitrogen-14
Diagram Calcium-40
Valence Electrons

Electrons in the __________________ energy level.
 Ex: Li = 1, F = 7
 Corresponds with the group number for Groups 1-2, 13-18.
Lewis Dot Structures
 Show __________________ electrons.
 Look at the __________________ number. This is how many dots you draw for each atom.
Ex:
Potassium
Fluorine
Sulfur
Xenon
Phosphorous
Silicon
Aluminum
Beryllium
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