Download chapter 7: atomic structure and periodicity

CHAPTER 7: ATOMIC STRUCTURE AND PERIODICITY
7.1 Electromagnetic Radiation
Electromagnetic radiation – radiant energy that exhibits _________________ behavior as it travels through space at
the speed of light in a vacuum.
All waves share common features:
Wavelength (λ) - ____________________ between 2 successive crests or troughs
Frequency (ν) - the number of _____________ (cycles) per second that pass a certain point. (unit:
Speed (c) – speed of light = _______________________________
)
Equation:
Wavelength and frequency are ____________________________ proportional.
7.2 The Nature of Matter
Wave model of light cannot explain
1) The emission of light from hot object
2) Photoelectric effect – the emission of electrons from metal surfaces
when light strikes it.
Max Planck theorized that energy can either be released or absorbed by
atoms in discrete “packets” of some minimum size (a quantum)
Equation:
Energy and frequency are ____________________________ proportional.
Einstein later theorized that light behaves as both a wave and a stream of particles called ____________________.
This phenomenon is often referred to as the ________ nature of light.
If light can exhibit particulate behavior, can matter that is normally assumed to be particulate exhibit wave behavior?
Louis de Broglie derived the following relationship of a particle with momentum:
This equation, known as de Broglie’s equations, allows us to calculate the wavelength for a particle.
EXAMPLE PROBLEMS:
Calculate the de Broglie wavelength for each of the following:
a) a proton with a velocity of 90.% of the speed of light.
b) a 150 g ball with a velocity of 10. m/s.
17.3 The Atomic Spectrum of Hydrogen
Continous spectrum – includes all ____________________ within a given range
Line spectrum (also called emission spectrum) show only certain wavelengths.
Line spectrum of hydrogen:
The line spectrum of hydrogen indicated
only certain ____________ are allowed
for the electron in hydrogen. In other
words, the electron energy levels are
quantized.
17.4 The Bohr Model
According to Bohr
1) Electrons can occupy only certain circular _________________ around the
nucleus.
2) Each orbit has an energy associated with it.
3) Energy is absorbed by an electron when it moves from a _____________ to
_____________ orbit. Energy is released (in the form of photons) when a emoves from a _______________ to ______________________ orbit. (E = hν)
4) The energy of the photons emitted or absorbed is equal to the difference
between the 2 orbit energies.
This explains why only certain lines of specific wavelengths appear on a line
(or emission) spectrum.
The most important equation to come from Bohr’s model is the one used to calculate energy associated with a
certain energy level (“orbit”).
E=
n = an integer  refers to _________________ , the larger the value of n, the _______________ the ___________.
Z=
ground state –
excited state –
Example Problem
a) Calculate the energy required to excite the hydrogen electron from level n = 1 to level n = 2
b) Calculate the wavelength of light that must be absorbed by a hydrogen atom in its ground state to reach this
excited state.
7.5 The Quantum Mechanical Model of the Atom
Problems with Bohr’s model :
A New Model – Quantum (Wave) Mechanical Model.
A mathematical model developed by __________________________, ____________________________, and
___________________ treats the electron as if it were a _____________________.
______________________ originated the idea that small particles, such as the electrons show wave properties.
Equation:
______________________ developed a wave equation in terms of wave function. His equation predicts the presence of certain
regions in the atom where electrons are likely to be found. These regions are known as____________________________ and
are 3 dimensional. The first 3 of the 4 quantum numbers were developed from this equation.
____________________________ developed the ________________________ principle which states that it is not possible to
simultaneously determine the position and momentum of a particle, such as an electron.
7.6 QUANTUM NUMBERS/7.8 ELECTRON SPIN AND PAULI EXCLUSION PRINCIPLE
Quantum numbers describe the various properties of ______________________________.
1. Principal Quantum Number – symbol
– has integral values 1,2,3,…..∞
The principal quantum number is
related to the _________________ and ____________________ of the orbital. As n increases, the orbital becomes
_________________ and has ________________ energy and is located _____________________ from the nucleus.
The sets of orbitals with the same n-value are often referred to as electron shells or energy levels.
2. Angular Momentum (Orbital) Quantum Number – symbol
- has integral values from 0 to n-1 for each value of n.
This quantum number refers to the sublevels that occur within each energy level and indicates the shape of the orbital.
3. Magnetic Quantum Number – symbol
- has integral values between _______ and _________,
including zero. The value of ___________________ is related to the orientation of the orbital in space
relative to the other orbitals in the atom.
4. Spin Quantum Number – symbol
- describes the apparent spin of the electron. Only 2 possible values,
______________ or ___________ (corresponding to the clockwise or counterclockwise spins.)
Pauli Exclusion Principle – states within an atom, no 2 electrons can have the same set of ___________ _______________.
Examples:
1) Write an acceptable set of quantum numbers for the one electron of hydrogen in its ground state.
2) Write an acceptable set of quantum numbers for the valence electron of highest energy in a sodium atom in its
ground state.
3) Write an acceptable set of quantum numbers for the valence electron of highest energy in a boron atom in its
ground state.
7.7 ORBITAL SHAPES AND ENERGIES
What are degenerate orbitals?
Hund’s Rule – orbitals of ___________ energy (degenerate orbitals) are each occupied by a ____________
Electron (with parallel spins) before any one orbital is occupies by a ______________ electron.
Paramagnetic – contains one or more _____________ electrons – attraction towards a magnetic field.
Diamagnetic – all electrons are _____________________ - weak repulsion by a magnetic field.
Ex. Which would be attracted to a magnetic field – Fe or Zn?
7.11 The Aufbau Principle and the Periodic Table (Part 1)
Aufbau Principle - (means “building up” ) According to the principle, electrons fill orbitals starting at the lowest
available (possible) energy states before filling higher states (e.g. 1s before 2s)
Types of electron configurations
1. Orbital Notation – use lines ___ or boxes
to represent orbitals and arrows
Write the orbital notation for the carbon atom.
to represent electrons.
2. Complete Electron Configuration - start with 1s orbital and use subscripts to represent # of e- present in sublevel.
Write the complete e- configuration for the calcium atom.
3. Noble Gas (shorthand) Configuration - use the previous noble gas to represent part of the electron configuration.
Write the noble gas configuration for the bromine atom
Write the noble gas configuration for the Hafnium (Hf) atom.
HOMEWORK
(All to be done on notebook paper)
HW 10/3
In book, pp. 340-41 #17, 37, 38, 39, 40,42, and 43
HW 10/4
1. Neutron diffraction is used in determining the structures of molecules.
a) Calculate the de Broglie wavelength of a neutron (1.675 x 10-27 kg) moving at 1.00% of the speed
of light.
b) Calculate the velocity of a neutron with a wavelength of 75 pm.
2. Calculate the wavelength of light emitted when the following transition occurs in the hydrogen atom:
a) n = 4  n = 2 .
b) n = 5  n = 4
HW 10/5
Read Sect. 7.10-7.13 pp. 316-338 for Reading Quiz Monday 10/8
HW 10/8
1. Which of the following orbital assignments are incorrect : 1s, 1p, 7d, 9s, 3f, 4f, 2d ?
2. Which of the following sets of quantum numbers are not allowed in the hydrogen atom? For the sets of
quantum numbers that are incorrect, state what is wrong in each set.
(a) n = 3, l =2, ml = 2
(b) n = 0, l =0, ml = 0
(c) n = 4, l =3, ml = 4
(d) n = 2, l =-1, ml = 1
3. Give the maximum number of electrons in an atom that can have these quantum numbers:
(a) n = 0, l =0, ml = 0
(d) n = 2, l =2
(b) n = 2, l =1, ml = -1, ms = -1/2
(e) n=1, l =0, ml = 0
(c) n = 3
HOMEWORK ASSIGNMENT 10/10
1. Give a possible set of 4 quantum numbers for all the valence electrons in an atom of arsenic in its
ground state.
2. Which of the following sets of quantum numbers are allowed? For sets that are incorrect, state what
is wrong.
(a) n = 7, l =7, ml = 0
(c) n = 7, l =0, ml = 1
(b) n = 7, l =5, ml = -3
(d) n = 3, l =-1, ml = 0
3. Which of the following electron configurations corresponds to an excited state? Identify the atoms and write the
ground state electron configuration where appropriate.
(a) 1s22s23p1
(c) 1s22s22p43s1
(b) 1s22s22p6
(d) [Ar] 4s23d54p1
4. Write orbital notations for the following atoms:
(a) Nitrogen
(b) Magnesium
5. Write complete electron configurations for the following atoms:
(a) Chlorine
(b) Strontium
6. Write the shorthand electron configurations for the following atoms:
(a) Pb
(b) As
(c) W
7. Is cadmium paramagnetic or diamagnetic? Justify your answer.
(d) Cf