Atomic Structure Summary

Atomic Structure Summary - Transcript

Chapter 4 Atomic Structure
Studying Atoms
Studying atoms is tough because
Therefore scientists must use
Ancient Greek Models of Atoms
Aristotle s beliefs
Thought that all substances were built up from
Did not think that there was a limit to the number of times
Democritus
Believed that all matter consisted of
He called the small particles
He thought there were different types of atoms with
Ex Liquids
Ex Solids
Dalton s Atomic Theory
John Dalton studied
Studied the behavior of
Based on the way that gases exert pressure he concluded that

Evidence for Atoms
He gathered evidence such as measuring masses of elements that
He noticed that compounds have

Dalton s proposed a theory that
All elements are
All atoms of the same element have
Compounds contain atoms of
Thomson s Model
Like charges
Some charged particles can flow from one location to another this is called an
Thomson used an electric current to learn more about atoms
He used
A
Metal disks
Wires connecting the disks as the source of
When the current is turned on 1 disk becomes
A glowing beam then

Thomson hypothesized that the beam was a stream of charged particles that
The plates caused the beam to
Concluding that the particles in the beam were
He called these negative particles

Thomson s experiment provided the first evidence that atoms are
Conclusion
The atom is
Ex Chocolate chip ice cream model
Rutherford s Model
Discovered that uranium produces fast moving particles that have a
He named them
The Gold Foil Experiment
He aimed a narrow beam of alpha particles at
He placed a screen around the foil that when struck by fast moving particles would
In doing the experiment some particles were


This led him to believe that the positive charge of an atom is not
They are concentrated in a very small dense central area called

Rutherford proposed a new atomic model
All of an atom s positive charge is
If an atom had the same volume as a baseball stadium the nucleus would have the same volume as a
Answer Section 4 1 Assessment Questions 1 8 Include question in your answer
Subatomic Particles are
There are 3 of them
Protons are
Each nucleus must contain
ii Each proton is assigned a charge of
Electrons are
Each electron has a charge of
Neutrons are
Have a mass almost exactly equal to that of a
Comparing Subatomic Particles
Protons neutrons and electrons can be distinguished by

Protons neutrons have almost the same
About 2000 electrons would equal the mass of

Everything scientists know about the nucleus subatomic particles is based on
The atomic number of an element equals

Ex Hydrogen atoms
Remember atoms of different elements have different
Remember each positive charge in an atom is balanced by a
Therefore the atomic of an element also equals the
The mass number of an atom is the
Ex Aluminum atoms have 13 protons 14 neutrons therefore the mass
is
If you know the atomic and the mass of an atom you can find the of neutrons by
of n mass atomic
Isotopes have the same number of
Ex Every atom of O has 8 protons Some O atoms have 8 neutrons a mass
of 16 Some have 9 neutrons a mass of 17 and some have 10
neutrons a mass of 18
These isotopes are referred to as oxygen 16 oxygen 17 oxygen 18
With most elements it is hard to notice any differences in the physical or chemical properties of their isotopes
Homework
Page 112 1 9 Include your question in your answer
Bohr s Model of the Atom
Bohr added on to Rutherford s model by placing
The electrons move with constant speed in fixed orbits around
The possible energies that electrons in an atom can have are called
The closer the electrons are to the nucleus the
Electron Cloud Model
Bohr s model was improved as scientists made further discoveries
An electron cloud is a visual model of the
Homework
Page 121 M C s 1 10 Q A
Page 121 Understanding Concepts s 11 20 22 28 29 31 Include question in answer
Page 123 1 4 Q A