Answer Key Integrated Chemistry Ch 4 Section 2 Review Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic (sound) and surface waves (water ripples). VOCABULARY Complete each of the following sentences using the following terms: Bohr's model, diffraction, excited state, ground state, interference, orbital, or quantum theory 1. The bending of a wave as it passes by the edge of an object is called diffraction. 2. When waves overlap each other, wave interference occurs. 3. The wave properties of electrons and other very small particles are described mathematically by quantum theory. Schrödinger equation 4. The three-dimensional region around the nucleus, an orbital, indicates the probable location of an electron. Describe the contributions of each of the following experimenters to our understanding of the atom. 1. Louis de Broglie hypothesized that electrons have wavelike properties. Other investigators verified his theory by proving that electrons can be bent or diffracted. In his 1924 PhD thesis he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as wave- particle duality or the de Broglie hypothesis. He won the Nobel Prize for Physics in 1929. 2. Werner Heisenberg developed uncertainty principle which is one of the fundamental building blocks of our understanding of light and matter. The principle is named after him and states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle. Heisenberg was awarded the Nobel Prize in Physics for 1932 "for the creation of quantum mechanics" 3. Erwin Schrödinger developed an equation that treats electrons like waves. His equation along with the Heisenberg uncertainty principle laid the foundation for modern quantum theory. Nobel Prize for Physics (1933) - for the formulation of the Schrödinger equation 4. Neils Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research. Write true or false for each of the following statements. false 1 In its ground state, an atom has its highest possible energy. Lowest 2 An atom is in an excited state when it has a higher potential energy than it has in its ground true state. 3 In Bohr's model of the atom, the orbit is the path taken by the atom’s protons around the false nucleus. Electrons 4 Quantum theory is a scientific explanation for the fact that hydrogen atoms give off only true certain frequencies of light. Circle the letter of the best answer. 1. Which of the following statements is true? a. Diffraction experiments showed that electrons behave more like particles than like waves. b. Wave functions give only the probability of finding an electron at a given place around the nucleus. c. All atomic orbitals have the same shape and size. d. Bohr’s model of the hydrogen atom is the accepted modern theory for the shape and behavior of atoms. 2. Which of the following statements is not true? a. Interference results in an increase of energy in some areas and a decrease of energy in others. b. Photons and electrons have about the same amount of energy. c. Only waves of specific frequencies provide solutions to the Schrödinger wave equation. d. Quantum theory proves that electrons act more like particles than like waves. 1. What are quantum numbers? Quantum numbers indicate the energy, location, shape, and orientation of atomic orbitals, as well as the spins of atomic orbitals. Fill in the chart to show what each quantum number indicates. Quantum Number Symbol What Number Indicates Principal quantum n the main energy level occupied by the electron Angular momentum l the shape of the orbital Magnetic quantum m the orientation of an orbital around the nucleus Spin quantum s the two fundamental spin states of an electron in an orbital Circle the letter of the best answer. 1. Which of the following indicates the s sublevel in the third main energy level? a. s3 b. 3xyz c. s3 d. 3s 2. Which of the following statements is true? a. A single orbital holds at least two electrons. b. The total number of orbitals at a main energy level increases as n increases. c. The number of orbitals at each main energy level is twice the principal quantum number. d. As n increases, the electron’s energy increases and its average distance from the nucleus decreases. .