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Bohr predicted that the energy of an electron in a hydrogen atom is E = - k ____ n 2 E is the energy of the e - k is the Bohr Constant, 2.178 x 10 -18.

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Presentation on theme: "Bohr predicted that the energy of an electron in a hydrogen atom is E = - k ____ n 2 E is the energy of the e - k is the Bohr Constant, 2.178 x 10 -18."— Presentation transcript:

1 Bohr predicted that the energy of an electron in a hydrogen atom is E = - k ____ n 2 E is the energy of the e - k is the Bohr Constant, 2.178 x 10 -18 J n is the Bohr Orbit For energy values: Positive means repulsive energy (because it’s a high value) Negative means attractive energy (because it’s a low value) Therefore, an e - s energy in an atom will always be negative EX3-1 (of 10)

2 Calculate the energy of an e - in the 3 rd Bohr Orbit of a hydrogen atom E = - k ____ n 2 = -2.420 x 10 -19 J=-2.178 x 10 -18 J ___________________ 3 2 EX3-2 (of 10)

3 Calculate the energy change when an e - drops from n = 2 to n = 1 in a hydrogen atom. E 2 = - k ____ n 2 = -5.445 x 10 -19 J=-2.178 x 10 -18 J ___________________ 2 2 E 1 = - k ____ n 2 = -2.178 x 10 -18 J ___________________ 1 2 EX3-3 (of 10)

4 The energy change (ΔE) is equal to the final energy state minus the initial energy state: ΔE = E 1 - E 2 = (-2.178 x 10 -18 J) – (-5.445 x 10 -19 J) Calculate the energy change when an e - drops from n = 2 to n = 1 in a hydrogen atom. = -1.634 x 10 -18 J For changes in energy: Positive means energy was absorbed Negative means energy was released Therefore, this hydrogen atom released energy EX3-4 (of 10)

5 The energy released is given off as a photon, and the photon’s energy is the absolute value of ΔE: Calculate the energy change when an e - drops from n = 2 to n = 1 in a hydrogen atom. E photon = | ΔE │ = | -1.634 x 10 -18 J │ = +1.634 x 10 -18 J EX3-5 (of 10)

6 If an electron is removed from an atom, the atom has been IONIZED Calculate the ionization energy of a ground state hydrogen atom E 1 = - k ____ n 2 = -2.178 x 10 -18 J ___________________ 1 2 E out =0 J EX3-6 (of 10)

7 ΔE = E out - E 1 = (0 J) – (-2.178 x 10 -18 J) = +2.178 x 10 -18 J If an electron is removed from an atom, the atom has been IONIZED Calculate the ionization energy of a ground state hydrogen atom The positive energy change means that the hydrogen atom absorbed this energy to release the electron EX3-7 (of 10)

8 Measuring the Wavelengths in Hydrogen’s Emission Spectrum EX3-8 (of 10)

9 e = λ sin = e/d d sin = e = λ EX3-9 (of 10)

10 tan = x/l = tan -1 (x/l) remember: λ = d sin λ = d sin [tan -1 (x/l)] EX3-10 (of 10)

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