Download Interpreting Atomic Structure

Atomic Structure Model Timeline
Dalton
1803
Thomson
1897
Rutherford
1911
Bohr
1913
Cloud
1926
Dalton’s Model (p.161)
Dalton proposed the first model of atoms; he thought atoms were a
solid sphere
Dalton’s Atomic Theory
1) All elements consist of atoms that cannot be divided
2) All atoms of the same element are exactly alike. Atoms
of different elements are different.
3) An atom of one element cannot be changed into an
atom of a different element.
4) Compounds form when atoms of more than one
element combine in a specific ratio.
Only points
(2) and (4)
are still true
today!
Thomson’s Model (p. 162)
Thomson suggested that atoms had negatively charged electrons set in a
soft positive sphere. Each electron is represented by the symbol e.−.
Think of Thompson’s model like a ball of chocolate chip cookie dough. It
is also called the “plum pudding” model.
Can you think of any other analogies for Thomson’s model?
Rutherford’s Gold Foil Experiment (p.162)
If atoms were a soft positive sphere, alpha particles fired at it should have
punched straight through. Rutherford was surprised that a few particles were
deflected strongly. Which are the paths of the particles that were not predicted
by Thomson’s atomic model?
Rutherford’s Gold Foil Experiment (p.162)
Use the diagrams to compare the expected and observed results of
Rutherford’s gold foil experiment.
Rutherford’s Model (p. 163)
The gold foil experiment resulted in the discovery of the nucleus.
According to Rutherford’s model, an atom was mostly open space.
The “6+” in the model means that there are six protons in the nucleus.
Bohr’s Model (p. 163)
Niels Bohr tested Rutherford’s model by observing the light emitted by
the element hydrogen.
Bohr’s Model (p. 163)
His results suggested that electrons move in specific orbitals around
the nucleus of an atom like planets orbiting the sun.
Modern Model of the Atom
Now we understand that orbitals are not “set in stone” as Bohr thought. Rather,
electrons move in cloudlike regions referred to as energy levels. We also know
that atoms are made up of protons, neutrons, and electrons.
.
Electron Cloud
This is the closest
we have been able to come
to visualizing the parts of
the atom. This image is
a mathematical projection
of the electron cloud(s)
around an atom, based
off experimental mass and
charge measurements. The
nucleus is too small and
dense to visualize.
Particles in an Atom
An atom is made up of protons, neutrons, and electrons. What is the
correct charge for each atomic particle?
So…what about QUARKS?
Well, the charges of protons, neutrons, and electrons have to
come from SOMEWHERE…
https://www.youtube.com/watch?v=nlv06lSAC7c
Believe it or not, the parts of the atom CAN be split!
QUARKS are the fundamental particle from which protons,
neutrons, and electrons are made.
Interpreting Atomic Structure
Each block on the periodic table contains a chemical symbol, element
name, atomic number, and mass number.
For example, Potassium has the symbol “K,” (2) an atomic number of 19 (1) and
an atomic mass of 39.098 (3) amu. Bananas are rich in potassium!.
Interpreting Atomic Structure
Atomic Number
- number of protons in an atom
- tells you which element you have
Mass Number
- total number of protons and neutrons
- number of neutrons equals the mass number
minus the atomic number
Electrons
- number of electrons in an atom is the same as the
atomic number (number of protons)
Isotopes
An isotope is an atom with fewer or more neutrons than usual.
The mass number on the periodic table is actually a weighted average of
the masses of the isotopes of that element.
What is the missing information for each isotope, below?
14
6
7
Ions
An ion is an atom with fewer or more electrons than usual.
Ions with a positive charge have fewer electrons than protons. Ions with a
negative charge have more electrons than protons. How would you find the
number of electrons if you knew the charge and atomic number of an ion?
Let’s Practice!
Example Video
https://www.youtube.com/watch?v=G3ImfVYSxoc
Remember!
Atomic Number = #Protons OR #Electrons
Atomic Mass = #Protons + #Neutrons
Now complete the worksheet “atomic structure basics”