11.2 – atomic emission spectra (c – level). chemists think they’re cool…
TRANSCRIPT
11.2 – ATOMIC EMISSION SPECTRA
(C – LEVEL)
CHEMISTS THINK THEY’RE COOL…
OBJECTIVES
WWBAT…
• Explain atomic emission spectra
• Determine the possible energies of photons emitted from an atom
PRISMS AND RAINBOWS
LET’S TAKE A LOOK AT COLORED FLAMES…
ATOMIC EMISSION SPECTRA
• Fingerprint of an element
• Occurs when an element is excitedand allowed to return to its ground state
FORMATION OF ATOMIC EMISSION SPECTRA
FORMATION OF ATOMIC EMISSION SPECTRA
• As an electron moves up energy levels, it increases its energy
• Energies closest to the nucleus have large, negative energies (remember, PEelec = kqq/d)
• Atoms, theoretically, have an infinite number of energy levels, with n = infinity having an energy of zero.
DETERMINING THE WAVELENGTH OR FREQUENCY
Ei – Ef = energy of photon (hƒ)
*NOTE: in advanced texts, frequency is denoted by the Greek letter nu, which looks a lot like a v. The TexasEduation Agency has decided frequency is denoted by the fancy f, whose name is unbeknownst to me.
*Additional fun fact: in advanced texts, potential energyis not denoted by “PE,” but by the letter U. The more youknow…
EXAMPLE
The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom?
A) 48.36 eV
B) 40.8 eV
C) 21.6 eV
D) 7.36 eV
E) 3.20 eV
EXAMPLE
The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom?
A) 48.36 eV
B) 40.8 eV
C) 21.6 eV
D) 7.36 eV
E) 3.20 eV
Transition to… n = infinity n = 4 n = 3 n = 2
n = 4
n = 3
n = 2
n = 1
EXAMPLE
The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom?
A) 48.36 eV
B) 40.8 eV
C) 21.6 eV
D) 7.36 eV
E) 3.20 eV
Transition… n = infinity n = 4 n = 3 n = 2
n = 4 4.2 eV
n = 3 6.04 eV 1.84 eV
n = 2 13.6 eV 9.4 eV 7.36 eV
n = 1 54.4 eV 50.2 eV 48.36 eV 40.8 eV
EXAMPLE
The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom?
A) 48.36 eV
B) 40.8 eV
C) 21.6 eV
D) 7.36 eV
E) 3.20 eV
Transition… n = infinity n = 4 n = 3 n = 2
n = 4 4.2 eV
n = 3 6.04 eV 1.84 eV
n = 2 13.6 eV 9.4 eV 7.36 eV
n = 1 54.4 eV 50.2 eV 48.36 eV 40.8 eV
CHECK YOURSELF
The following diagram illustrates the energy levels for an atom. A photon of which energy would not be able to be emitted from this atom?
A) 13.6 eV
B) 12.1 eV
C) 10.2 eV
D) 6.45 eV
E) 1.12 eV
CHECK YOURSELF
The following diagram illustrates the energy levels for an atom. A photon of which energy would not be able to be emitted from this atom?
A) 13.6 eV
B) 12.1 eV
C) 10.2 eV
D) 6.45 eV
E) 1.12 eV
OBJECTIVES
WWBAT…
• Explain atomic emission spectra
• Determine the possible energies of photons emitted from an atom