Chapter 4 - Atomic structure
Lavoisier (1743-1794)

Helped turn_______________into an __________________________________


Verified the _________________________________________________________
Beheaded in ____________________________ Revolution (worked as a tax collector)- this pretty much stopped
his career as a scientist
Early Models of the Atom


Democritus (a Greek Professor)

First suggested the existence of ______________________________________that make
up____________

Named ____________
John Dalton (a scientist)

Studied the ratios in which ____________ combine in _________________________

Based his ideas on results of his __________________________________________
Dalton’s Atomic theory

All matter is composed of ___________________________called ___________________

Atoms do not change their________________________ when they undergo ___________________

Elements have only____________________________, all with the ______________________. Elements of
different atoms are ___________________.

Compounds are composed of two or more elements combined in____________________________________.

Chemical reactions involve the __________________________ of atoms to give
new______________________________. Atoms are not ____________________________________________.
Structure of the Atom


Discovered by__________________________ (Late 1890’s)

________________________ flowed through a ______________________________

Subatomic particles were attracted by a_________________charged plate – therefore, they had to be
_____________

Even though atoms are _______________ ____________they contain definite negative charged particles, which
we now know as _______________________________.

This led to a model of the atom known as the “__________________________”
Ernest Rutherford

Trying to find ___________________________to support the ________________________

“shot” _________________________________at a very thin layer of _____________________

Alpha particles (helium nuclei) have two relevant features here:

They have a lot of _____________________ (mass x speed)

Most alpha particles went ____________________________

Some were deflected off at _______________

Very few ______________________________________________(Rutherford this was as surprising as
seeing a cannonball rebound from a sheet of tissue paper)

How to explain this (what could affect the positive alpha particle’s path sometimes but not often?)

They have a_______________________________
The Nuclear Atom

An atom with a __________________________of positive charge (_______________________) around
which tiny electrons moved in a space that was otherwise empty

The nucleus contained positively charged ___________.

Neutron

Chadwick

Subatomic particle with slightly more _______ than a proton but has no ________
Subatomic Particles



Protons

charge is __________

location ___________
Neutrons

charge is __________

location ___________
Electrons

charge is __________

location ___________
Atomic Number


The number of ___________ in the nucleus of the atom

The atomic number identifies the element
Atoms are electrically neutral

# of __________ = # of __________
Mass Number

The total number of __________ and __________ in the nucleus of an atom
Interpreting Symbols
27
Al
13

Aluminum- 27
Sample Problems

How many protons, neutrons and electrons are in an atom of Be-9?


Protons = _____ Electrons = _____ Neutrons = _____
How many protons, neutrons and electrons are in an atom of Ne-20?

Protons= ______ Electrons= ______ Neutrons= ______

an atom or group of atoms that have a _________ or ________ charge

An ion has either gained or lost electrons
Ions

A positive ion has______ electron(s)


Called: ___________
A negative ion has ______ electron(s)

Called: ___________
Class work:
In your textbook complete the following questions:
Pg 111 #15 and 16
Pg 112 #17 and 18
Bohr Model

Niels Bohr

Sought to explain the ______________________________in more detail

Often called the_______________________________________

It is _______________(Atoms are not like little solar systems)

We can’t predict or know the exact _________________________ and________________ of an electron
# of Electrons in a Bohr Model

1st Energy level contains __________electrons

2nd Energy Level contains ________electrons

3rd Energy Level contains_________ electrons

4th Energy Level contains ________electrons
Draw Silicon:
Isotopes

atoms of the same element that differ in the number of _________________ in the nucleus

Because isotopes of an element have different numbers of neutrons, they have different __________
numbers.
Sample Problems

Two isotopes of carbon are carbon-12 and carbon-14. Write the symbol for each isotope using subscripts and
superscripts. Determine the number of protons, neutrons and electrons for each isotope

Two isotopes of oxygen are oxygen-16 and oxygen-18. Write the symbol for each isotope using subscripts and
superscripts. Determine the number of protons, neutrons and electrons for each isotope
Weighted Average Atomic Mass
Real-Life Application:

Calculate marking quarter grade:

Test 80

Quiz 90

HW 100
*What would the average be if all categories were weighted equally?
*What if the breakdown was as follows:
Tests 50%
Quiz 30%
HW 20%
Average Atomic Mass
Sample Problems

What is the atomic mass of silicon if 92.21% of its atoms have mass 27.977u, 4.70% have mass 28.976u and
3.09% have mass 29.974u?

Find the average atomic mass for silver if 51.83% of silver atoms have mass 106.905 and 48.17% of atoms have
mass 108.905?