Chem Exam 1/5/17 Review Questions & Answers (PART TWO)

Which of these elements has an atom with the most stable outer electron configuration?

(1) Ne in order for a valence shell to be considered stable, it must have 8 valence electrons. Remember 8 is great, which means that an atom with 8 valence electrons is satisfied.

An electron in an atom moves from the ground state to an excited state when the energy an electron...

(1) increases. In order for an electron to move from ground state to excited state it must gain energy. Just think about if you get excited, it means there is an encase in energy. This means an electron will move from a low energy level to a higher one.

Which electron configuration represents an atom of chlorine in an excited state?

(2) 2-8-6-1 this is the excited state of Chlorine, on the periodic table the ground state is 2-8-7. The excited state electron configuration is showing an electron leaving one energy level and moving up to a higher level.

During a flame test, ions of a specific metal are heated in the flame of a gas burner. A characteristic color of light is emitted by these ions in the flame when the electrons...

(2) Whenever the problem states that "light was emitted" it indicates that the electrons are moving from a high energy level to a low energy level. They are going back down to ground state. I order to return to a lower energy level, electrons must lose energy.

What is the total number of electrons in the valence shell of an atom of aluminum in the ground state?

(3) 3. The electron configuration for Al is 2-8-3 which indicated 3 electrons in the valence shell.

The characteristic spectral lines of an element are caused when electrons in an excited atom move from...

(3) We see the emission spectra, spectral lines when electrons move from higher energy levels to lower energy levels. When electrons move from a high energy level to low energy level they release energy. This could also be known as electrons moving from excited state to ground state.

Which Lewis electron-dot structure is drawn correctly for the atom it represents?

(4) Ne has 8 valence electrons which is accurately depicted by 8 dots on the lewis dot structure of He.

How many electrons are in the outermost principal energy level of an atom of carbon in the ground state?

(4) The electron configuration for Carbon in the ground state is 2-4 so this tells us that there are 4 valence electrons (outermost principal energy level = valence shell)

What is an electron configuration of a sulfur atom in the ground state?

(4) The electron configuration for S(sulfur) 2-8-6

Identify the two gases in the unknown mixture

Gas A and Gas D: Both have lines that are represented in the unknown mixture. In order to solve this type of problem you must match up the lines with the unknown ,mixture given. If all the lines of the element can be found in the mixture then that element is part of the mixture.

Explain the production of an emission spectrum in terms of the energy state of an electron.

The production of an emission spectrum occurs when energy is being released by an electron. ** Since the question asks you to state the answer in terms of energy, you must state what happens in terms of energy** Don't say: The electrons move ( that doesn't state anything about energy)**