Test on Monday, 19 November will cover all of Chapter 4 and the entire ion table.
Chapter 4 Section Review - Modern Chemistry
Section 4-2
1. d
2. a
3. a
4. c
5. c
6. c
7. c
8. Scientists knew that any wave confined to a space could have only certain frequencies. DeBroglie suggested that electrons should be considered as waves confined to the space around an atomic nucleus; in thhis way, electron waves could exist only at specific frequencies. According to the relationship E = h x nu, these frequencies correspond to the specific energies of the Bohr orbitals.
9. The principal quantum number refers to the main energy level. The angular momentum number refers to the type of orbital the electron is in. The magnetic quantum number refers to which orbital contains the electron. The spin quantum number distinguishes between the two electrons that any orbital can hold.
10. Because the exact position of the electron is not known, it must be assumed that the electron takes up the entire space in an orbital.
11.
1 1 s
2 2 s,p
3 3 s,p,d
4 4 s,p,d,f
Section 4-3
1. The Pauli exclusion principle states that no two electrons in an atom may have the same four quantum numbers. Hund's rule states that orbitals of equal energy are each occupied by one electron before a second electron can enter an orbital.
2. This orbital notation is possible if an electron in helium's orbital has been excited.
3. 1s2 2s2 2p6 3s2 3p3 + orbital notation
4. 1s2 2s2 2p3 + orbital notation
5. 1s2 2s2 2p6 3s2 3p6 4s1 + orbital notation
6. 1s2 2s2 2p6 2s2 3p1 + orbital notation
7. 1s2 2s2 2p6 2s2 3p6 + orbital notation
8. 1s2 2s2 2p1 + orbital notation
9. a) Pauli exclusion principle; b) Hund's rule
Mixed Review
1. A photon is emitted when an electron moves from a higher-energy level to a lower-energy level.
2. Quantum numbers describe the location, type of orbital, and spin properties of electrons.
3. The principle quantum number, n, describes the energy level. For example, the electrons at 2p6 are at the energy level represented by n=2.
4. The most stable arrangement of electrons is one with the maximum number of unpaired electrons.
5. No two electrons can have the same set of four quantum numbers.
6. Electrons from from the s orbital will sometimes be promoted to a higher energy level in order to create half filled or filled d orbitals.
7. The colors are created by photons released by an electron as the electron makes the transition from a higher energy level to a lower energy level.
8.a) 1s2 2s2 2p2
8.b) 1s2 2s2 2p6 3s2 3p6 4s1
8.c)1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
8.d) 1s2 2s2 2p6 3s2 3p6 4s1 3d10
9. 1 x 1012 m using c=lamba x nu (remember to us 1/sec for Hertz when substituting into the formula).
Section 4-1
1. In order for an electron to be ejected form a metal surface, the electron must be struck by a single photon with at least the minimum energy needed to knock the electron loose.
2. The ground state is the lowest energy state the electron can occupy. When the electron absorbs energy, it can move to a higher energy level, or excited state.
3. A photon is emitted when an electron moves from the excited state to the ground state.
4. The frequency of the light is equal to E/h. The energy of the photon represents the difference between the energy of an electron's excited state and the energy of its ground state.
5. Energy is proportional to frequency and ultraviolet radiation has a higher frequency than infrared radiation. To produce ultraviolet radiation, electrons must drop from higher energy levels than electron transitions that produce infrared radiation.
6. The wave on the right has the higher frequency. Wavelength is inversely proportional to frequency, so as the wavelength decreases, its frequency increases.
7. Photons were emitted six times. Each time an excited helium atom falls back from an excited state to its ground state or to a lower energy state, it emits a photon of radiation that shows up as this specific line emission spectrum. There are six lines in this helium spectrum.
8. 9.7 x 1014 Hz
9. 9.4 x 109 m