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Electron Configuration
Chapter 5. Sec 5.1 Electrons in atoms
1. In the 1900s scientists observed that certain elements emitted visible light when
heated in a flame. The analysis of that flame revealed that the chemical behavior
is related to the arrangement of the electrons in its atom.
2. Scientists also observed that light behave somehow like the electrons.
Understanding light behavior helped them in explaining how electrons behave.
3. What is that scientists discovered regarding to the element’s chemical behavior?
Scientists discovered that an element’s chemical behavior is related to the
arrangement of the electrons in its atoms.
4. How does light travel?
In waves in a pattern called electromagnetic radiation (through space)
5. What is electromagnetic radiation?
It is a form of energy that exhibits wavelike behavior as it travels through space
6. If light travels in waves, which are the characteristics of waves?
Waves have four characteristics: amplitude, wavelength, frequency and speed.
7. How is frequency measured?
Frequency tells you how fast a wave moves in a second.
8. How is wavelength measured?
It is the distance between equivalent points on a continuous wave. Crest to crest or
trough to trough
9. How is amplitude measured?
It is the wave’s height from the origin to a crest or trough
10. How fast electromagnetic waves travel including light?
Light moves at a speed of 3 x 108 m/s
11. Light differ from other types of waves because it travels at a constant speed
C= wavelength (λ) x frequency (υ) (formula to calculate speed of light in vacuum).
12. How are wavelength and frequency related?
Inversely, Long wavelength low frequency; short wavelength high frequency
13. What is the electromagnetic spectrum?
Since waves travel at different speeds and therefore have different frequencies and
wavelengths. The electromagnetic spectrum encompasses all the forms of
electromagnetic radiation.
14. What is a quantum?
A quantum is the minimum amount of energy that can be gained or lost
15. Who came up with that concept?
Max Plank
16. Plank was able to predict how the emission of different colors of light was
produced when heating objects. As molecules were agitated they shifted in speed
and in wavelength producing different colors. In other words, he found the
relationship that exists between the frequency and wavelength of a particular type
of radiation to the energy it carries.
17. This relationship was expressed in what is known as the Plank’s constant
Energy = Plank’s constant x frequency (E=hv)
v= Plank’s constant (6.62 x 10-34 J/sec)
18. His findings were the base knowledge that led Einstein to discover that energy is
carried by photons. Each photon or particles of light can only carry certain quanta
(amount of energy). This explanation aid in understanding the effects of different
kinds of electromagnetic radiation.
19. Einstein used Planck’s equation to explain what the photoelectric effect was.
In the photoelectric effect, electrons are ejected from the surface of a metal when
light shines on the metal. He then proposed that light consists of quantifiable energy
in the form of photons. This helped in understanding the effects of the different waves
produced in the electromagnetic spectrum. High frequency energy or high quantified
photons are damaging.
20. What is a line spectrum?
It is a portion of the spectrum that contains certain colors or wavelengths. Some
elements emit light when vaporized in a flame. The line spectrum is also known as
the atomic emission spectrum (kind of a finger print of an element).
Section 5.2 Quantum Theory
21. Bohr Model. Bohr postulated that to get spectral lines, the energy of the electron
must be quantized (measured). Using Rutherford’s model, he labeled each energy
level with a quantum number called “n.” The lowest energy level known as the
ground state had a quantum number of one, meaning n= 1. This is the energy level
closest to the nucleus. When an electron absorbs energy it is said to be in an
excited state and moves to a higher-energy levels called n=2, 3, 4-7 etc.
22. Louis de Broglie analyzed Bohr’s ideas and suggested that electrons had wavelike
motion and that electrons move in certain wavelengths frequencies and energies.
He created a formula that calculates the probability of finding the electron ( λ=
h/mv) Page 150.
23. After analyzing Broglies and Bohr’s ideas, Werner Heisenberg stated that it is
impossible to know precisely the velocity and position of a particle at the same
time, therefore difficult to know the exact position of the electron.
24. The Heisenberg uncertainty principle states that it is fundamentally impossible to
know precisely both the velocity and position of a particle at the same time.
25. Schodinger, an Australian physicist created a model where electrons are treated as
waves called the wave mechanical model of the atom or the quantum mechanical
model of the atom. As a result instead of the circular orbits a 3-D region around
the cloud was called the atomic orbital. An atomic orbital is the region around the
nucleus of an atom where an electron is likely to be found
26. The cloud is most dense where the probability of finding the electron is higher
and that is called the electron density
27. The principal quantum number “n” indicates the relative size and energy of
atomic orbitals. As n increases the orbital becomes larger. According to Bohr
there 7 energy levels (shells).
28. Principal energy levels contain energy sublevels named s, p, d, f; each sublevel
have different shapes. S orbitals have a spherical shape, p orbitals have a
dumbbell shape and d, or f orbitals have different shapes and orientations.
Section 5.3 Electron Configuration
29. Electron spin: electrons have particular energies and they spin on their own axis.
The spin can be clockwise or counter clock wise. The spin of the electron creates
a magnetic field.
30. In 1925 Wolfgang Pauli stated the importance of the electron spin in determining
how electrons are arranged. Pauli Exclusion Principle stated that a maximum of
two electrons may occupy a single atomic orbital.
31. Hund’s rule states that negatively charged electrons repel each other, so electrons
with the same spin must occupy each equal-energy orbital before electrons with
opposite spin occupy the same orbital (page 157)
Example: 1s1
2s2
32. Orbital diagrams
Orbitals can be represented by boxes, each box is labeled with the principal
quantum number n= 1, 2, etc. Each box should have the sublevels particular to each
energy level s, p, d, f, these boxes are to be filled with arrows up an down
representing the electrons found in each level (p. 158).
33. Electron configuration notation is a shorthand method for describing electron
arrangement using the Aufbau principle. The Aufbau principle states that each
electron occupies the lowest energy orbital available
34. Noble-gas notation is a form of representing electron configurations of noble
gases using bracketed symbols (p. 159).