```4.5 Trends & Periodicity
What is periodicity?
Period (horizontal trend) : ____________________
Why? As the number of protons increase, the __________________________ increases.
As the nuclear charge ____________________, the attraction between the positive nucleus and
negative electron cloud increases
Group(vertical trend): __________________
Why? the electrons are added in new ________________________. The inner electrons “shield” the
new outer electrons from the pull of the ________________ therefore it doesn’t pull as strongly.
Examples:
List the following in INCREASING order of atomic radius . Li Cs K
List the following in DECREASING order of atomic radius . Ca Be Ba Sr
Who has the largest atomic radius? Mg Cl, Na P
Trend 2: Ionization Energy
Ionization Energy is defined as:
Period (horizontal trend) : ____________________
Why? Moving left to right, the _________________ of the atom decreases as more protons pull on
more electrons. When an atom is ____________________, the electrons are ________________ to the
nucleus, and therefore feel the pull more strongly. THUS it is harder to pull electrons away from these
smaller atoms
Group(vertical trend): __________________
Why? As you move down a group, the radius increases as more ______________________ are
added. As the outer electrons (those involved in bonding) are farther from the ______________, they
will feel the “pull” of the nucleus _________________. Thus it is easier to remove an electron from a
larger atom.
Examples:
List the following in INCREASING order of ionization energy . Li Cs K
List the following in DECREASING order of ionization energy . Ca Ba Be Sr
Who has the highest ionization energy? Cl Na I In
Trend 3: Electronegativity
Electronegativity is defined as:
Period (horizontal trend) : ____________________
Why? When an atom is smaller, the _________________ pulls more strongly. This can attract & draw
an electron ________________ from another atom.
Group(vertical trend): __________________
Why? The larger atom is less able the nucleus is to ______________________ electrons away from
another atom.
Examples:
Who has the highest electronegativity . Ba Br Ca
List the following in decreasing order of electronegativity . I, Cl, Br
Trend 4: Ionic Radii & Charge
An ion is defined as:
 Cations are _______________ ions resulting from the ___________ of electrons.
 Anions are __________________ ions resulting from the __________ of electrons
Cations are smaller than neutral atoms!
Why? When electrons are lost, there are now more ______________________ than electrons.
Therefore, the protons have a _____________________ “pull ” on each of the electrons.
Anions are larger than neutral atoms!
Why? When electrons are gained, there are now more ____________________ than protons.
Therefore, the protons have a _____________________ “pull” on each of the electrons.
Period (horizontal trend) : ____________________
Group(vertical trend): __________________
***** Notice it’s the same trend as atomic radii!****
Examples:
Arrange in order of decreasing ionic radius.
P-3 Mg+2 Cl-1
Arrange in order of increasing ionic size: K+1 Cs+1 Li+1
Trend 5: Reactivity
Reactivity is defined as:
For Metals
Period (horizontal trend) : ____________________
Group(vertical trend): __________________
Why? The more reactive metals have the ____________________ ionization energy
For NonMetals
Period (horizontal trend) : ____________________
Group(vertical trend): __________________
Why? The most reactive nonmetals have the ______________________ ionization energy and
electronegativity
4.6 Light
Electromagnetic radiationis all _____________________ that exhibits wavelike behavior and
travels through space.
 Examples are: ____________________________________________
 All energy travels at the speed of light which equals _____________________
Electromagnetic Spectrum (EM spectrum)
c
 Identifies all forms of electromagnetic radiation
=


Wave Properties

________________________() is the distance from trough to trough of a wave
(measured in meters “m”)
 ________________________ () is the number of times a wave completes a cycle in
one second (cycles per second is “Hertz” or “Hz”)
 Notice that the shorter the wavelength, the __________________ the frequency. This is
a __________________ relationship
 Using the EM SPECTRUM above, notice as frequency increases, the amount of energy
_____________________. This is a _____________________ proportional
relationship.
 ________________________ is a small region within the spectrum that has
wavelengths/frequencies that are eyes can detect.
 ROY G BIV is a mnemonic to help you remember the colors of the spectrum. Red is
near _________________ and violet is near ultra violet.
Examples using Reference Sheet
1. Which of the following forms of electromagnetic radiation has the shortest wavelength?
a) gamma
b) visible
c) infrared
2. As the frequency of electromagnetic radiation increases, its wavelength ______________.
a) increases
b) decreases
c) remains constant
d) is impossible to determine.
3. Which of the following forms of radiation has photons with greatest amount of energy?
a) red light
b) yellow light
c) green light
d) violet light
4. What type of electromagnetic radiation is represented by a wavelength of 1870 nm?
a) infrared
b) visible light
c) ultraviolet
d) x-ray
5.
What type of electromagnetic radiation is represented by a wavelength of 4.7x10-1 m?
a) gamma rays
b)infrared
c)microwaves
d) visible light
Continuous Spectrum vs. Line Spectrum
 Continuous Spectrum: Sunlight (or white light) will produces a _______________ of
color because there are no _____________ wavelengths.
 Line Spectrum is when _______________________ atoms emit light of only certain
____________________. Each element has its own line spectrum.
 How can a line spectrum be explained?
 Energy packets called _______________ or quanta come in contact with an atom and
collide with an electron
EXCITATION: this is the process of an electron __________________ a photon of light and
being promoted to a higher energy level from its _________________ state
 The electron cannot remain in the excited state indefinitely SO
RELAXATION: the process of an electron ______________________ the photon of light it
absorbed and falling back down to a lower energy level.
 The higher the Energy of a photon, the greater the jump. For example, a photon of
__________________ light would have more energy than infared light so there would be
a higher jump. See diagram below.
The TOTAL ENERGY IN = TOTAL ENERGY OUT
 If an atom absorbs a large photon of energy that moves it up 2 energy levels, it will
release the exact same amount of energy but it can be released in smaller packets
moving the electron back down in ______________________ manner.
 The energy of the photon must ___________________match the energy change of an
electron. If it does not match, the energy passes through the electron with no change.
Hydrogen Line Spectrum: The colored lines are the wavelengths of light that were emitted when
the electron’s moved from a higher to a lower energy level. The blue line is a result of the
electron moving from the 4th to the 2nd energy level.
 Bohr’s study of light gave him the proof that atoms had fixed energy levels.
Examples using the Reference Sheet
1. On the energy level diagram below, draw an arrow representing the electron in
hydrogen’s ground state being excited to the fourth energy level.
2. An electron in the hydrogen atom makes the transition n = 5  n = 3.
a. Determine the wavelength of light associated with this transition. Include units.
a) 434 nm
b) 434 m
c) 1282 nm
d) 1282 m
b. Classify the type of electromagnetic radiation this wavelength represents:
a) infrared
b) visible light
c) ultraviolet
d) x-ray
c. Is this energy emitted by the atom or absorbed by the atom?
__________________
Flame Tests
 ___________________ can be identified by the _______________ of light they emit.
When metals absorb energy from a flame, the ________________ absorb energy and
their____________________, they release the energy they absorbed in the form of
______________________. The wavelength of light of some metals fall in the
_____________ light portion of the spectrum. This allows us to see their color.
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