AP Course Outline Quiz # 1 p. 1
Name ___________________________ date _____
Atomic Structure
Historical Perspective For each person list their significant contribution to advancing the model of the atom.
Cite the evidence that lead to this contribution.
Scientist
Dalton
Contribution to Model of Atom
Evidence
Atomic Theory – smallest particle of
matter – an atom – indivisible and
indestructible
Conservation of mass and combine in simple
whole # ratios
Thomson
Plum Pudding Model: Electrons –
negative – embedded in positive matrix
Rutherford
Nuclear Model: dense positive nucleus
surrounded by orbiting electrons
Bohr
Electrons orbit nucleus in orbit of
increasing energy as distance from
nucleus increases
Energy level = n = increasing n
increasing distance and PE
Calculate the energy of electron as it
moves up and down
Cathode ray tube – discovers electrons
bend towards positive pole
charge to mass ratio –suggest e-much smaller
than atoms
Gold Foil experiment – shot alpha particles
(Helium nuclei) at gold foil – most went through
a few deflected back – must have hit dense
positive nucleus
Emission spectrum of hydrogen
And other single electrons species
Atoms emits only distinct bands of light with no
color between
Mass spectrometer provides evidence about the relative abundance of different isotopes of an element.
Identify the most abundant isotope of strontium. Sr- 88
a) What does the mass number tell you about
this isotope?
Mass # = # protons + # neutrons
88
= 33 + # neutrons
b) How many protons does this isotope of Sr
have?
Atomic # = 38 so 38 protons
c) How many neutrons does this isotope of Sr
have?
88 - 38 = 50 neutrons
Isotope
Strontium-84
Strontium-86
Strontium-87
Strontium-88
Molar Mass, g
83.913
85.909
86.909
87.906
Percent Abundance
0.56
9.86
7.00
82.58
Calculate the molar mass of
strontium. Show your complete
calculation below.
0.56/100 (83.913) + 9.86/100 (85.909) + 7.00/100 (86.909) 82.58/100 (87.906) =
87.617 g/mol
Solution:
Natural strontium consists of the following isotopes:
Isotope
Strontium-84
Strontium-86
Strontium-87
Strontium-88
Molar Mass, u
83.913
85.909
86.909
87.906
Percent Abundance
0.56
9.86
7.00
82.58
Calculate the molar mass of strontium.
The molar mass is the weighted average:
Molar mass
=
(83.913 g/mol)(0.0056) + (85.909 g/mol)(0.0986) +
(86.909 g/mol)(0.070) + (87.906 g/mol)(0.8258)
=
87.634 g/mol
AP Course Outline Quiz # 2 p. 2
Wave and Particle Model
Name ___________________________ date _____
Electromagnetic Radiation – Two competing models: wave and particle
Wave Model.
1) As wavelength decreases, the frequency __increases_
This is a __ inverse ___ (direct or inverse relationship)
2)
As wavelength decreases, the frequency __increases_
This is a __ inverse ___ (direct or inverse relationship)
3) Write the equation that relates wavelength and
frequency to the speed of light.
speed of light = wavelength x frequency
Note: speed of light = c
4) Write the equation that relates energy and frequency to the speed of light.
Energy = Planck’s constant x frequency Note: Planck’s constant = h
5) The hydrogen emission spectrum shows four bands within the visible light spectrum: red, green, blue
and violet. Which color represents the atom emitting the most energy?
Violet with the shortest waves has the highest frequency and therefore the most energy of these four colors.
6) Describe the behavior of the electrons in the hydrogen atom as energy is absorbed and released
according to the Bohr model.
Negative electrons are attracted to the positive protons in the nucleus. The electrons will have the
lowest potential energy when they are closest to the nucleus. (Visualize a bowling ball attracted to
earth and raised to a height above the earth – the higher it raised the more PE it has and thus the less
stable it becomes.) Bohr proposed that electrons are located in distinct orbits around the nucleus.
Bohr proposes that electrons could be in these orbits but
not in between. The atom in the ground state has
electrons in the lowest orbits possible – that is closest to
nucleus. When hydrogen atoms absorb energy the
electrons may jump up to higher level. The electrons gain
PE and are thus less stable. The electrons will fall back
down to lower orbits and releases that PE as KE in the
form of electromagnetic radiation – ranging from waves
too long to be observed by our eyes (infrared) to waves
too short (ultraviolet) and the visible spectrum of colored
light between. To explain the colored bands of light
observed from excited hydrogen atoms we will address
only the movement to the second orbit (n=2). When an
electron falls from n=3 to n=2, red light is emitted. When
an electron falls from n=4 to n=2, green light is emitted.
When an electron falls from n=5 to n=2, blue light is
emitted. When an electron falls from n=6 to n=2, violet
light is emitted.
Use the Bohr’s constant(En = 2.179 x 10-18 J/n2) and the equation (Ephoton= Ef – Ei =
ΔE) to calculate the energy as an electron falls from level 4 (n=4) to level 2 (n=2). Explain
why the sign of the change in energy is negative.
En = -2.179 x 10-18 J/n2
∆ E = Ef - Ei = -2.179 x 10-18 J/22 - -2.179 x 10-18 J/22
= -2.179 x 10-18 (1/22 - 1/42) = -4.088 x 10-19 J
We can also calculate the frequency and the wavelength associated with this transition.
E=hf
E/h = frequency = 6.165 x 1014 s-1
c = λƒ
c / ƒ = λ = 3 x 108 m/s / 6.165 x 1014 s-1
7) Describe Planck’s proposal for a particle model of light.
Planck's constant: Energy is not continuous.
Around 1900, Max Planck from the University of Kiel concerned himself with observations of the
radiation of heated materials. He attempted to draw conclusions from the radiation to the radiating
atom. On basis of empirical data, he developed a new formula which later showed remarkable
agreement with accurate measurements of the spectrum of heat radiation. The result of this formula
was so that energy is always emitted or absorbed in discrete units, which he called quanta. Planck
developed his quantum theory further and derived a universal constant, which came to be known as
Planck's constant. The resulting law states that the energy of each quantum is equal to the frequency of
the radiation multiplied by the universal constant: E=f*h, where h is 6.63 x 10-34 Js. The discovery of
quanta revolutionised physics, because it contradicted conventional ideas about the nature of radiation
and energy.
8) Describe the photoelectric effect as explained by Einstein using a particle model of light.
Light shining on a metallic surface can generate an electrical current (flow of charge) due to the
movement of electrons. Energy is required to move electrons down a wire to pull electrons away from
one atom (ionization energy). Green light shined on the metal generates a current while a red light does
not regardless of duration or brightness. Explanation – each photon of red light that hits the metal does
NOT have enough energy to pull off the e- and cause the electrons to move down the wire. The effect is
not cumulative suggesting a particle model (or discrete explanation –particle model rather than a
continuous one – wave model)
AP Course Outline Quiz # 3 p. 3
Quantum Mechanics Model of the Atom
Name ___________________________ date _____
As a consequence of de Broglie’s matter/wave duality ---….. The wavelength of matter is a function of
its mass. Electrons with so little mass have wave-like properties that cannot be ignored.
State Heisenberg’s Uncertainty Principle.
Due to the wave nature of e-, it is impossible to determine both location and energy of
e- at the same time. This leads to Schrodinger equations of wave functions to
calculate probable locations of electrons – the cloud (orbital).
Schrodinger’s wave functions use calculus to predict the probable locations of electrons within orbitals.
First quantum number, n, tells you about …
n indicates the energy level – distance from the nucleus.
This was the only quantum number from the Bohr model.
l=0
l=2
l=1
The only possible value
Second quantum number, l, tells you about …
l
indicates the shape of the orbital – the s, p, d, f shape
l=3
Third quantum number, ml, tells you about …
l = 0 ( s orbital ) ml = 0 the only possible value since = - l …0...+ l
l = 1 ( p orbital ) ml = -1, 0,+1 three possible values since = - l …0...+ l
l = 2 ( d orbital ) ml = -2,-1 0,+1,+2 five possible values - l ..0..+ l
l = 3 ( f orbital ) ml = -3,-2,-1 0,+1,+2, +3 seven possible values - l ..0..+ l
Fourth quantum number, m s, tells you about …
Two electrons repel each other but they can be together in the
same orbital with opposite spins.
Pauli Exclusion Principle – no two electrons can be assigned
same set of four quantum numbers.
the
In the first energy level (n=1), what are the possible values of l? What kind of orbitals?
Since l = n – 1, then if n = 1 the only l is 0 so only s orbital
In the second energy level (n=2), what are the possible values of l? What kind of orbitals?
Since l = n – 1 … 0, then if n = 2 the only l = 1 and 0 so both p and s orbitals in level 2
In the third energy level (n=3), what are the possible values of l,? What kind of orbitals?
Since l = n – 1 … 0, then if n = 3 the only l = 2, 1, and 0 so both d, p and s orbitals in level 3
If
l = 0, is this a s, p, d, or f orbital? _s__
What are the values of m l? How does this relate to the
number of orbitals?
ml = 0 the only possible value since = - l …0...+ l
so only one s orbital per energy level
If
l = 1, is this a s, p, d, or f orbital? _p__
What are the values of m l? How does this relate to the
number of orbitals?
ml = -1, 0, +1 three possible value since = - l …0...+ l
so only three p orbitals per energy level
If
l = 2, is this a s, p, d, or f orbital? _d__
What are the values of m l? How does this relate to the
number of orbitals?
ml = -2, -1, 0, +1, +2 five possible value
since = - l …0...+ l
so five p orbitals per energy level
An electron found in a 2p orbital – give a set of four possible quantum numbers to “locate” this electron.
2 1 -1 +1/2
An electron found in a 4s orbital – give a set of four possible quantum numbers to “locate” this electron.
An electron found in a 3d orbital – give a set of four possible quantum numbers to “locate” this electron.
Draw the electron configuration for arsenic.
AP Course Outline Quiz
Periodic Properties
Name ________________________
date___________
ELECTRON CONFIGURATION PATTERNS ON PERIODIC TABLE
1 Barium (Ba). In column __IIA_ has its last electron in ___s____ (s, p, d, or f) orbital. How many
electrons in that orbital? ___2___ What is the energy level of the orbital? __6___
2) Arsenic (As). In column _IIIA__ has its last electron in ___p__ (s, p, d, or f) orbital. How many
electrons in that orbital? ___3__ What is the energy level of the orbital? __4___
ELECTRONEGATIVITY
3) Define electronegativity. Electronegativity is a measure of the attraction of an atom for
electrons in a covalent bond.
4) Nitrogen is in the same column as arsenic (in #3).
Since they are in the same column, what is the same? Both have 3 electrons in p orbital
Where is nitrogen’s last electron? Level 2
Where is arsenic’s last electron? Level 4
Which atom has a greater electronegativity: N or As? Justify using electrical force.
Nitrogen is more electronegative than Arsenic. Since arsenic’s last electron is farther from the nucleus
(in level 2 vs level 4), the electrons experience less electrical force pulling between the positive protons
in the nucleus pulling on the negative electrons. Electrical force depends directly on charge and
inversely on distance. The distance factor is squared, though so it exerts a greater influence. So even
though arsenic has more positive protons, the distance is shorter for nitrogen thus the electrons
experience a greater electrical force pulling inward. In addition to this distance factor there is also an
electron shielding effect as there are three inner layers of electrons between the last electron in arsenic
and its nucleus, whereas nitrogen has only one inner layer of electrons.
Which atom is bigger? Justify.
Arsenic is bigger since it has four layers of electrons. Nitrogen only has electrons in level 2, much
closer to nucleus and smaller atom.
5) Bromine is in the same row as arsenic (in #3).
Since they are in the same row, what is the same? The last electron is in same level n=3.
What is the difference? Br has 5 e- in p orbital and As has only 3 e- in p orbital.
Which atom has a greater electronegativity: As or Br? Justify using electrical force.
Since both atoms have electrons in the same level – the distance factor is no longer a factor in the
electrical force that pulls the electrons in towards the positive nucleus. Arsenic with 33 protons pulling
inward has less charge thus less electrical force. Electrical force depends directly on charge and
inversely on distance. The distance factor is squared, though so it exerts a greater influence. So
bromine with more positive protons (17), the electrons experience a greater electrical force pulling
inward.
Which atom is bigger? Justify.
Arsenic is pulling. Since bromine has the greater number of protons pulling the electron cloud in in the
same level, the cloud is pulled in smaller.
IONIZATION ENERGY
6) Define ionization energy.
The energy needed to remove one or more electrons from a neutral atom to form a positively charged
ion is a physical property that influences the chemical behavior of the atom. By definition, the first
ionization energy of an element is the energy needed to remove the outermost, or highest energy,
electron from a neutral atom in the gas phase. Second ionization energy is the energy to remove the
second electron. The second ionization energy is always greater than the first since the electron must be
removed from an ion with a net positive charge. If the electron is also removed from a lower energy
level, the ionization energy is significantly greater than removing the prior electron.
7) Calcium is in the same column as barium (in #2).
Since they are in the same column, what is the same? Both have two electrons in s orbital
Where is calcium’s last electron? In level 4
Where is barium’s last electron? In level 6
Which atom has a greater ionization energy Ca or Ba? Justify using electrical force and energy.
Since Barium’s last electron is farther from the nucleus (in level 6 vs level 4), the electrons experience
less electrical force pulling between the positive protons in the nucleus pulling on the negative electrons.
Electrical force depends directly on charge and inversely on distance. The distance factor is squared,
though so it exerts a greater influence. So even though barium has more positive protons, the distance is
shorter for calcium thus the electrons experience a greater electrical force pulling inward. In addition to
this distance factor there is also an electron shielding effect as there are five inner layers of electrons
between the last electron in barium and its nucleus, whereas calcium has only two layers of electrons.
Thus less energy is required to break the attraction between barium and its last electron – so it has a
lower ionization energy.
8) Cesium is in the same row as barium (in #6).
Since they are in the same row, what is the same? Last electron in same level n=6.
What is different? Cs has only 1 e- in s whereas Ba has two.
Which atom has a greater ionization energy: Cs or Ba? Justify using electrical force and energy.
Since the distance factor has been eliminated (last e- in same level), the greater charge – more protons in
the barium nucleus results in a greater electrical force pulling in the electrons of barium. So it take more
energy to remove barium’s last electron. Cesium has a lower ionization energy – less energy required to
pull off e-. Though the second ionization for cesium would be much more than the first since the second
electron would be removed from a level closer to the nucleus.