Transcript 3. atomic structure

SUBATOMIC PARTICLES
Particle
Charge
Mass
Location
Proton
+1
1 amu
Nucleus
Neutron
0
1 amu
Nucleus
Electron
-1
1/1836 or
0 amu
Outside
Nucleus
Rutherford’s Gold Foil Experiment
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Most alpha particles went
straight through
Some of the particles
deflected back to the
source.
Conclusion:
1. Atom made up mostly of
empty space.
2. Nucleus has an overall
positive charge.
Bohr’s “Planetary” Atom Model
Wave-Mechanical Model
Orbit vs. Orbital

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An orbit describes a particular path that an object
follows as it travels around another object
For example, the moon has an orbit about the
earth
Electrons do not follow a particular path around
the nucleus
Instead, an orbital describes the areas around the
nucleus where an electron is most likely to be
found (probability of location)
The exact path of an electron in this area is not
known
ISOTOPES

Atoms of the same element that have different
numbers of neutrons.

There are two methods of identifying isotopes. 1.
Write mass number with a hyphen after the
name of the element, ex: Helium-3 or Helium-4,
and 2. using the composition of the nucleus as
the isotopes nuclear symbol, ex. 3He or 4He (the
number of the bottom left would represent the
atomic number which is the number of protons,
and therefore never changes.
Atomic Mass

The average of all the naturally occurring
isotopes of an element.
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MUST know how to calculate it!!!!

Ex: Naturally occurring chlorine is 75.78% 35Cl,
which has an atomic mass of 34.969 amu, and
24.22% 37Cl, which has an atomic mass of
36.966 amu. Calculate the average atomic mass
(that is, the atomic weight) of chlorine.
hello dr mcguiness ;D

FIRST PRINCIPLE ENERGY LEVEL: holds only 2
electrons.
 SECOND PRINCIPLE ENERGY LEVEL: holds only
8 electrons.
 THIRD PRINCIPLE ENERGY LEVEL: holds only 18
electrons.
 FOURTH PRINCIPLE ENEGY LEVEL: holds only
32 electrons.

Valence Electrons - The number of electrons in the last
principle energy level. According to the octet rule, there
can be no more than 8 valence electrons. These electrons
affect chemical properties of the element.
Non-Valence Electrons - All other electrons in an atom other
than the last level (valence)
Ground vs. Excited States


In this class we will be performing an experiment called
the “Flame Test”. We will be heating up metal powders
in order to excite the electrons to jump from a lower
energy level to a higher energy level.
When an electron returns from a higher energy state to a
lower energy state, it emits a specific amount of energy
usually in the form of light. This is known as a bright line
spectrum, and can be used to identify an element like a
fingerprint.
Bright Line Spectrum

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While this light appears as one color to our eyes,
it is actually composed of many different
wavelengths each of which can be seen using a
spectroscope
The energy that is given off when an excited
electron falls to the ground state is separated into
its component wavelengths.
Ions

An atom with a charge.

We can never change the number of
protons! So to produce a charge we can
add or subtract electrons

Atoms lose or gain electrons in order to
have a complete outer shell (to become
more stable), and follow the octet rule.
Lewis Dot Diagrams

Helps to show the number of valence electrons in the last principle
energy level. There can only be 2 electrons on each side of the
symbol of the element.
1.
Put the 1st and 2nd valence electrons on any side of X.
2.
For the 3rd, 4th, and 5th electrons, put each electron on a
different side of the symbol.
3.
For the 6th, 7th and 8th electrons, add them to any side with 1
electron.