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ELECTRONS IN ATOMS
LIGHT
Light is a kind of electromagnetic _____________________. All forms of electromagnetic radiation
move at 3.00 x 108 m/s. The ______________ is the baseline of a wave. The crest is the high point on
a wave, and the trough is low point on a wave. The amplitude of a wave is the wave’s _____________
from the origin to a crest, or from the origin to a trough. Wavelength (represented by λ, the Greek
letter lambda) is the ___________________ distance between equivalent points on a continuous wave.
Wavelength is the distance from crest to crest or trough to trough and is usually expressed in meters
(m). _____________________ (represented by f ) is the number of “waves” that pass a given point per
second, and the units are cycles/sec or hertz (Hz)
c = fλ
c = the speed of light
Frequency and wavelength are __________________ related, which means that as one goes up the
other goes _____________. Different frequencies of light correspond to different colors of light. In
1900, the German physicist Max Planck began searching for an explanation as he studied the light
emitted from ___________________ objects. Matter can gain or lose energy only in small, specific
amounts called _______________. That is, a quantum is the minimum amount of energy that can be
gained or lost by a(n) ____________. That is, while a beam of light has many wavelike
characteristics, it also can be thought of as a stream of tiny particles, or bundles of energy, called
________________. Thus, a photon is a particle of electromagnetic radiation with no _____________
that carries a quantum of energy. Planck went further and demonstrated mathematically that the
energy of a quantum is ___________________ related to the frequency of the emitted radiation.
E=hf
E = energy of the photon (J – Joules); f = frequency (Hz); h is Planck’s constant = 6.63 x 10-34 J.s
The energy of radiation increases as the radiation’s frequency, f, __________________. Scientists
knew that the wave model of light could not explain a phenomenon called the ____________________
effect. In the photoelectric effect, electrons, called __________________________, are emitted from
a metal’s surface when light of a certain _______________________ shines on the surface. Einstein
proposed that for the photoelectric effect to occur, a photon must possess, at a minimum, the energy
required to _______________ an electron from an atom of the metal.
THE BOHR MODEL OF THE ATOM
Niels Bohr, a young Danish physicist working in Rutherford’s laboratory in 1913, suggested that the
single electron in a ___________________ atom moves around the nucleus in only certain allowed
circular orbits. The atom looked like a miniature _________________ system. The nucleus is
represented by the sun, and the electrons act like the planets. The orbits are circular and are at different
levels. Amounts of ___________________ separate one level from another. (Modern View: The
atom has two regions and is 3-dimensional. The nucleus is at the _________________ and contains
the protons and neutrons. The electron _________________ is the region where you might find an
electron and most of the volume of an atom.) Bohr proposed that electrons must have enough energy
to keep them in constant motion around the ___________________. Electrons have energy of motion
that enables them to overcome the attraction of the _________________ nucleus. Further away from
the nucleus means more energy. Electrons reside in ________________ levels.
THE QUANTUM MECHANICAL MODEL
Building on Planck’s and Einstein’s concepts of ____________________ energy (quantized means
that only certain values are allowed), Bohr proposed that the hydrogen atom has only certain allowable
energy ______________. The lowest allowable energy state of an atom is called its _______________
state. When an atom gains energy, it is said to be in a(n) __________________ state. When the atom
is in an excited state, the electron can drop from the higher-energy orbit to a _______________-energy
orbit. As a result of this transition, the atom emits a ____________________ corresponding to the
difference between the energy levels associated with the two orbits.
ATOMIC AND EMISSION SPECTRA
By heating a gas of a given element with electricity, we can get it to give off _______________. Each
element gives off its own characteristic colors. The spectrum can be used to __________________ the
atom. These are called line _______________. Each is unique to an element. The spectrum of light
released from excited atoms of an element is called the _________________ spectrum of that element.
As the electrons fall from the excited state, they __________________ energy in the form of light.
The further they fall, the ________________ the energy. This results in a higher frequency.
Use the Chemistry Reference Tables to answer the following:
(a) An electron falls from energy level 5 to 3. What is the wavelength of the light emitted?
(b) An electron falls from energy level 6 to 2. What is the wavelength of the light emitted?
(c) An electron falls from energy level 3 to 1. What type of electromagnetic radiation is emitted
(infrared, visible or ultraviolet)?
(d) An electron falls from energy level 4 to 2. What type of electromagnetic radiation is emitted
(infrared, visible or ultraviolet)?
(e) An electron falls from energy level 5 to 2. What color of visible light is emitted?
(f) An electron falls from energy level 3 to 2. What color of visible light is emitted?
MORE QUANTUM MECHANICAL MODEL
Like Bohr’s model, Schrodinger’s quantum mechanical model limits an electron’s energy to certain
values. The space around the nucleus of an atom where the atom’s electrons are found is called the
electron ________________. A three-dimensional region around the nucleus called an atomic
__________________ describes the electron’s probable location. In general, electrons reside in
principal ________________ levels. As the energy level number increases, the orbital becomes
_______________, the electron spends more time ___________________ from the nucleus, and the
atom’s energy level increases. Principal energy levels contain energy ___________________.
Principal energy level 1 consists of a single sublevel, principal energy level 2 consists of __________
sublevels, principal energy level 3 consists of three sublevels, and so on. Sublevels are labeled s, p, d,
or f. The s sublevel can hold 2 electrons, the p sublevel can hold _____ electrons, the d sublevel can
hold 10 electrons, and the f sublevel can hold 14 electrons. Sublevels contain __________________.
Each orbital may contain at most ________ electrons. There is one s orbital for every energy level,
and the s orbital is ____________________ shaped. They are called the 1s, 2s, 3s, etc… orbitals. The
p orbitals start at the second energy level, reside along ______ different directions and have 3 different
________________ shapes. The d orbitals start at the ________________ energy level and have ____
different shapes. The f orbitals start at the fourth energy level and have ______ different shapes.
ELECTRON CONFIGURATIONS
Electron configurations represent the way electrons are arranged in atoms. The Aufbau principle states
that electrons enter the __________________ energy first. This causes difficulties because of the
________________ of orbitals of different energies. At most there can be only 2 electrons per orbital,
and they must have __________________ “spins.” Hund’s rule states that when electrons occupy
orbitals of equal energy, they don’t _________ up with an electron of opposite spin until they have to.
Let’s determine the electron configuration for phosphorus. __________________________________
Let’s determine the electron configuration for chromium. ___________________________________
 Write the electron configuration for aluminum (Al). _____________________________________
 Write the electron configuration for neon (Ne). _________________________________________
 Write the electron configuration for calcium (Ca). ______________________________________
 Write the electron configuration for iron (Fe). __________________________________________
 Write the electron configuration for bromine (Br). ______________________________________
To identify an element with a given electron configuration, add the _________________ numbers
together and find the element with that atomic number.
 Identify the element with the following electron configuration: 1s2 2s2 2p6 3s2 3p4
 Identify the element with the following electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d9
 Identify the element with the following electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2
Electron Configuration Using a Noble Gas Abbreviation - In order to write this type of configuration,
find the _______________ gas (from Group 8A) that comes before the element in question. Put the
symbol for the noble gas in _____________________ and then write the part of the configuration that
follows to reach the desired element.
Write the electron configuration using a noble gas abbreviation for:
 magnesium (Mg) _________________________
• nickel (Ni) ________________________
 fluorine (F) _________________________
• silicon (Si) _______________________
 zirconium (Zr) _________________________
VALENCE ELECTRONS
The electrons in the ______________________ energy level are called valence electrons. You can
also use the periodic table as a tool to predict the number of valence electrons in any atom in Groups 1,
2, 13, 14, 15, 16, 17, and 18. All atoms in Group 1, like hydrogen, have __________ valence electron.
All atoms in Group 2 have two, in Group 13 have _______, in Group 14 have four, in Group 15 have
five, in Group 16 have six, and in Group 17 have ________ valence electrons. All atoms in Group 18
have eight valence electrons, except helium which only has two. All atoms in sublevels d and f have
_________ valence electrons.
 How many valence electrons does each of the following elements have?
a) carbon (C)
b) bromine (Br)
c) iron (Fe)
d) potassium (K)
e) aluminum (Al)
LEWIS DOT DIAGRAMS
Because valence electrons are so important to the behavior of an atom, it is useful to represent them
with symbols. A Lewis dot diagram illustrates ___________________ electrons as dots (or other
small symbols) around the chemical symbol of an element. Each dot represents _____________
valence electron. In the dot diagram, the element’s symbol represents the core of the atom - the
nucleus plus all the _______________ electrons.
 Write a Lewis dot diagram for
a) chlorine
b) calcium
c) potassium