College Chemistry : Introductory Topics

Study concepts, example questions & explanations for College Chemistry

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Example Questions

Example Question #3 :Electron Configurations

What is the electron configuration for?

Possible Answers:

Correct answer:

Explanation:

Start by finding the noble gas core. For tungsten, this will be xenon as this is the noble gas that is closest to it.

The normal electron configuration for如下:

Recall that electrons are lost in the highest energy level subshell first.

has lostelectrons. It will lose the first two electrons from theshell, then it will loseelectron from theshell, giving it the following electron configuration:

Example Question #4 :Electron Configurations

What is the electron configuration for?

Possible Answers:

Correct answer:

Explanation:

Start by finding the noble gas core. For iron, this will be argon as this is the noble gas that is closest to it.

Next, recall that since theorbitals are higher in energy that theorbitals, electrons will be lost from theorbital first.

The normal electron configuration for如下:

has lostelectrons. It will lose the first two electrons from theshell, then it will loseelectron from theshell, giving it the following electron configuration:

Example Question #5 :Electron Configurations

When an electron moves from a lower energy state to a higher energy state, the electron__________.

Possible Answers:

both absorbs and releases energy

absorbs energy

None of these. An electron cannot move from a lower energy state to a higher energy state.

neither absorbs nor releases energy

releases energy

Correct answer:

absorbs energy

Explanation:

Electrons of an atom are located within electronic orbitals around a nucleus. The electrons of each atoms have their own specific energy level called principal energy level. When electrons are excited by absorbing energy the electrons can jump to a high energy level. Then when an electron drops back to a lower energy level the electron emits the energy. Therefore, when an atom moves from a lower energy state to a higher energy state. the electrons absorb energy.

Example Question #6 :Electron Configurations

What is the full electron configuration of sodium?

Possible Answers:

Correct answer:

Explanation:

Each element has a unique electron configuration that represents the arrangement of electrons in orbital shells and sub shells. There are four different orbitals,s, p, d,andfthat each contain two electrons. Thep, d, andforbitals contain subshells that allow them to hold more electrons. The orbitals for an element can be determined using the periodic table. Thes-block consists of group 1 and 2 (the alkali metals) and helium. Thep-block consists of groups 3-18. Thed-block consists of groups 3-12 (transition metals), and thef-block contains the lanthanides and actinides series. Using this information we can determine the full electron configuration of sodium.

To do this, start at hydrogenlocated at the top left of the periodic table. Hydrogenand heliumare in the firstsorbital and account for. Next, we move to the seconds-orbital that contains lithium (Li) and beryllium (Be), which accounts for. Then we move to boron, carbon, nitrogen, oxygen, fluorine, and neon, which are all in thep-block and account for. There is no1porbital. Finally, we are at sodium, which is in thes-block and accounts for. Therefore the full electron configuration of sodium is.

Example Question #7 :Electron Configurations

What is the electron configuration of iodine in nobel gas notation?

Possible Answers:

Correct answer:

Explanation:

Each element has a unique electron configuration that represents the arrangement of electrons in orbital shells and subshells. There are four different orbitals,s, p, d,andfthat each contain two electrons. Thep, d,andforbitals contain subshells that allow them to hold more electrons. The orbitals for an element can be determined using the periodic table. Thes-block consists of group 1 and 2 (the alkali metals) and helium. Thep-block consists of groups 3-18. Thed-block consists of groups 3-12 (transition metals), and thef-block contains the lanthanides and actinides series. Using this information we can determine the electron configuration of iodine in nobel gas configuration.

The nobel gas configuration is a short hand to writing out the full electron configuration. To do this, start at the nobel gas that come before the element of interest. In the case of iodine, the nobel gas is krypton. Therefore, the electron configuration will begin with, and this will be the new starting place for the electron configuration.

After krypton comes thes-block, which contains elements with the atomic numbers 37 and 38 that account for. Then comes thed-block containing elements 39-48 that account for. Finally comes thep-block containing elements 49-53 that account for. Therefore, the electron configuration of iodine in nobel gas configuration is.

Example Question #1 :Quantum Numbers

Which of the following represents the absorption of a photon with the highest energy?

Possible Answers:

Electrons moving fromto

Electrons moving fromto

Electrons moving fromto

Electrons moving fromto

Electrons moving fromto

Correct answer:

Electrons moving fromto

Explanation:

The absorption of energy excites electrons to higher energy levels, from a lowerto a higher one. Since electron shells grow increasingly closer in energy andincreases, the highest gaps occur between lower level shells. Thus, in this question, the largest gap between any two principle quantum number occurs between the first energy level and the third energy level.

Example Question #2 :Quantum Numbers

Which of the following energy shells does not exist for any electron in either the ground or excited states?

Possible Answers:

Correct answer:

Explanation:

2d is a non-existent energy shell because its principle quantum number,, does not exceed its orbital angular momentum quantum number,. This is easily observable on the periodic table, where it is shown that the d-sub shell is only available for energy levels greater than or equal to three. All other answer choices obey the rule that the orbital angular momentum quantum number is less than the principle quantum number.

Example Question #3 :Quantum Numbers

What is the difference between the quantum numbers2nand4n?

Possible Answers:

2nand4nhave different orientations

2nis larger in size than4n

4nis larger in size than2n

4nhas a positive magnetic spinwhile2nhas a negative magnetic spin

2nis spherical while4nis dumbbell shaped

Correct answer:

4nis larger in size than2n

Explanation:

The correct answer is that4nis larger in size than2n.

When it comes to quantum numbers,nrefers only to size or the atom, or electrons' distance from the nucleus;nis the principal quantum number.

lis expressed asand is therefore dependent on thenvalue;ldescribes the shape of the orbital (spherical, dumbbell, etc.).

mlvalues range fromtoand describe the orientation of the orbital.

msvalues are eitherorand represent electron spin.

Example Question #4 :Quantum Numbers

The light emitted by neon atoms in a neon sign is caused by which of the following?

Possible Answers:

Electrons moving very quickly along a tube.

Electrons moving from a higher to a lower principal energy level.

Protons moving from a higher to lower principal energy level.

Neutrons moving from one atom to another.

Protons moving from one atom to another.

Correct answer:

Electrons moving from a higher to a lower principal energy level.

Explanation:

Electrons of an atom are located within electronic orbitals around a nucleus. The electrons of each atoms have their own specific energy level called principal energy level. When electrons are excited by absorbing energy the electrons can jump to a higher energy level. When an electron drops back to a lower energy level, the atom emits energy. Therefore, when neon atoms in a neon sign emit light, the electrons are moving from a higher principal energy level to a lower principal energy level.

Example Question #5 :Quantum Numbers

What is the frequency of the microwaves in a microwave oven, which have a wavelength of?

Possible Answers:

Correct answer:

Explanation:

To solve this problem we need to use the following equation:

where,

= speed of light =. The speed of light is constant.

= wavelength (units =)

= frequency (units =or)

Now we can plug the wavelength and the speed of light into the equation above and solve for frequency.

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