CHE 106 Exam 3 Questions

What is/are the expected charge/s of the commonly found indium ions?

+1 & +3.

What is the charge of the indium ion that has the ​[Kr]4d^10 electron configuration?

+3.

Consider the following equivalent resonance structures for the carbonate anion. Charges have not been shown. What is the average formal charge on each oxygen atom?

-0.67. In each resonance structure, two of the oxygen atoms have a -1 charge and one oxygen atom has a charge of 0 in each structure. The average would be: (-1 + -1 + 0)/3 = -2/3.

Draw the best Lewis structure for SF₄²⁻ and calculate the formal charge on sulfur.

-2

The Lewis structure of shows that the central phosphorus atom has ____ nonbonding and ____ bonding electron pair(s).

0,5

How many electrons are needed to fill a complete set of d orbitals?

10. There are five different d orbitals and each can contain two electrons for a total of ten electrons.

How many total valence electrons are present in NHO?

14

What is the maximum number of electrons that can have n = 3?

18. When n = 3, ℓ = 0, 1 or 2 (or s, p or d). s orbitals can hold 2 electrons, p orbitals can hold 6 electrons and d orbitals can hold 10 electrons for a total of 18.

How many dots should be used for the Lewis representation of magnesium?

2. The valence electron configuration of magnesium is [Ne]3s², so 2 dots should be used to represent the 2 valence electrons.

How many full waves span for the 4 harmonic n = 4?

2.0. A complete wave is traversed when going from one maximum through an adjacent minimum, starting and ending at the midline. The red and blue waves each do this twice.

How many valence electrons are present in H₂CO₃?

24. 2H(1e⁻) + 1C(4e⁻) + 3O(6e⁻) = 24e⁻

How many p-orbitals are occupied in a O atom?

3

Nitrogen has a 1s²2s²2p³ electron configuration. How many of nitrogen's electrons have ℓ = 1?

3. The 2p³ configuration is interpreted as three electrons that can be found in 2p orbitals or ℓ = 1. We shall see in the following section the actual configuration is 2px¹2py¹2pz¹. The remaining four electrons are in s orbitals (1s and 2s) and, therefore, have ℓ = 0.

What value of ℓ is not allowed for an electron in an n = 3 shell?

3. ℓ can equal any whole integer up to n-1. So in this case n = 3, ℓ can not equal 3.

The wavelength of a photon that has an energy of J is ____ m.

3.10E-8

The ion has ____ valence electrons.

36

How many valence electrons are present in SF₄²⁻?

36. 1S(6e⁻) + 4F(7e⁻) + 2⁻(1e⁻) = 36e⁻

What type of orbital does an electron with n = 3 and ℓ = 2 occupy?

3d. n = 3 sets the number 3 in the orbital type. ℓ = 2 sets the letter d (in spdf notation).

In carbon dioxide, carbon is the central atom (O-C-O). How many total bonds would carbon need to make with the oxygen atoms in order to achieve an octet while also allowing each oxygen atom to achieve an octet?

4. For all atoms in carbon dioxide to achieve an octet, carbon must make four total bonds with the oxygen atoms. In this way, carbon will have access to eight electrons (all shared) and each oxygen will have access to eight electrons (four unshared and four shared).

How many dots should be used for the Lewis representation of silicon?

4. The valence electron configuration of silicon is ​[Ne]3s²3p², so 4 dots should be used to represent the 4 valence electrons.

Convert 457 nm to meters.

4.57 × 10 m (457 nm x (10m/1 nm) = 4.57 x 10 m)

How many valence electrons does the ground-state configuration of nitrogen have?

5. 1s² are the core electrons. 2s²2p³ electrons (5 in total) are valence electrons.

How many d orbitals are there per single value of n (where n ≥ 3)

5. A d orbital corresponds to ℓ = 2 which means mℓ = -2, -1, 0, +1, +2. These 5 different values of mℓ give 5 different types of orbitals.

How many dots should be used in the Lewis representation of arsenic (As)?

5. The valence electron configuration of As is ​[Ar] 4s²4p⁵, thus As has five valence electrons.

Convert 457 nm to frequency.

6.56 × 10 s^-1. First convert 457 nm to meters: 457 nm x (10m/1 nm) = 4.57 x 10 m Then, divide the speed of light by the wavelength to yield frequency.

How many different f orbitals are there?

7. An f orbital has ℓ = 3; thus m = −3, −2, −1, 0, +1, +2, +3

As more energy impacts the metal surface, electrons are ejected at which of the following?

A higher kinetic energy. As more energy impacts the metal surface, hν increases. Because Φ is a constant for each metal, KE will correspondingly increase.

Which element has a partially filled atomic orbital?

Ag. The 5s orbital is partially filled.

What is the expected product formed from the reaction of calcium with antimony?

CaSb₂. Calcium has the highest metallic character so will lose its 4s²² electrons, acquiring a +2 oxidation state. Antimony needs to gain three electrons to acquire a 5p⁶ electron configuration and will have a −3 oxidation state. To get a neutral compound we therefore need three calcium atoms for every two antimony atoms. The name of this compound is calcium antimonide.

For the molecule carbon monoxide, which atom would you expect to have a partial positive charge?

Carbon. Carbon has a lower electronegativity value (X = 2.5) than oxygen (X = 3.5), so oxygen will draw the shared electrons toward itself leaving carbon electron-deficient.

The Bohr radius theoretically is the {__________ } distance an electron can approach the nucleus in the hydrogen atom.

Closest. Radius is directly proportional to n.

As n increases while holding ni constant, what happens to v?

Decreases. As n grows in value holding n fixed, the quantity within the parentheses gets smaller. This quantity gets multiplied by R, which yields a correspondingly smaller frequency

What is the apparent relationship between energy and frequency?

Directly proportional. As frequency increases, total energy appears to also increase. Hence, energy and frequency are directly proportional.

What color of light is associated with an energy of 3.865 x 10 J?

Green. Convert energy to wavelength. E = 3.865 x 10-19 J λ = 513.9 nm = green light

Why does it become difficult to mathematically describe the Coulombic interactions in a multi-electron atom?

Heisenberg's uncertainty principle makes it impossible to determine the exact location of the electrons.

The lowest orbital energy is reached when the number of electrons with the same spin is maximized. This statement describes ____.

Hund's Rule

What other periodic trends parallel electronegativity? I) Atomic sizeII) Ionization energyIII) Electron affinity

II) Ionization energy III) Electron affinity.

As n increases while holding nf constant, what happens to v?

Increases. As n grows in values holding n fixed, the quantity within the parentheses gets smaller. This quantity gets multiplied by R, which yields a correspondingly longer wavelength.

When waves constructively interfere, what parameter changes in the resultant wave?

Intensity. Constructive interference increases the amplitude. Wavelength and frequency do not change.

The relationship between wavelength and frequency can be described as

Inversely proportional. The speed of light is fixed. Therefore, as wavelength decreases, frequency must increase to maintain the constant. Hence, these values are inversely proportional.

Which ion has the largest ionic radii?

K+

If m is very small, then is {__________ }.

Large. m and λ are inversely proportional.

Any wavelength longer than that of an electron would be too large for imaging. It follows that a shorter wavelength electromagnetic wave would have a energy.

Larger. Recall that energy and wavelength are inversely proportional.

The less negative energy corresponds to an electron being {__________ } tightly held.

Less. A small magnitude of En corresponds to a large denominator, which is n. So, if n is very large, then we are further from the nucleus: a weakly held electron.

Determine which electron configuration is the excited state.

Magnesium - 1s²2s²2p⁶3s¹3p¹. Magnesium is a Group 2 element on period 3 and, thus, its electron configuration ends with a 3s² term. Its full ground-state electron configuration (that obeys Aufbau) is 1s²2s²2p⁶3s². It would appear that a 3s electron has been excited to a 3p orbital in the excited state configuration given in the question.

Of the following, which gives the correct order for atomic radius for Mg, Na, P, Si and Ar?

Na > Mg > Si > P > Ar

Which Lewis structure in Figure 8.16 has at least one atom without a full valence shell?

Neither

Which ion is not isoelectronic with the others?

Ne⁺. all isoelectronic with atomic neon except Ne⁺, it has an electron configuration 1s²2s²sp⁵

Which is the central atom of NHO?

Nitrogen

Which metal ion does not have a pseudo-noble gas configuration?

Ni²⁺

Which two elements have the same ground-state electron configuration?

No two elements have the same ground-state electron configuration.

Consider a bond between boron and oxygen. Which atom would you expect to bear the partial negative charge?

Oxygen. Oxygen is more electronegative than boron.

Which element has the highest electron affinity (most negative value)?

Oxygen. Oxygen is the only atom that tends to form anions and, therefore, has the highest electron affinity.

Position

Particle character (a wave has no true position, as it is a continuous entity)

Which of the following are false statements?

Photons of UV radiation have less energy than photons of IR radiation. "A" is true. As temperature increases, the total area under the curve increases. "B" is true. The T curve has its peak maximum at the highest frequency, which is equivalent to shorter wavelengths. "C" is false. UV photons are more energetic than IR photons. "D" is true. Energy and wavelength are inversely related.

What colors of light involve less energy than green light?

Red, orange, yellow. Since energy is directly proportional to frequency, any color shown to the right of green will involve less energy.

Which element has the most negative electron affinity?

S. Electron affinity increases towards the top right hand corner of the periodic table.

Which is the central atom in SF₄²⁻?

S. Sulfur is less electronegative than fluorine.

Is the wavelength small or large relative to the size of a bullet?

Small

If you wanted to use light to spot an electron's location, the electromagnetic wave you use (as in a microscope) would need to have a wavelength than the electron's de Broglie wavelength.

Small. Any wavelength longer than that of an electron would be too large for imaging.

An electron in the hydrogen atom is excited from the ground state to the n = 4 state. Which of the following are true statements?

The electron is farther from the nucleus in the = 4 state than the ground state & The wavelength of light absorbed for n= 1 → n= 4 is the same as that emitted for n = 4 → n= 1. "A" is false. The first excited state is n=2. "B" is false. n=4 is higher than the ground state. "C" is true. An electron is closest to the nucleus when in the ground state. "D" is true. The magnitude of the energy change is the same.

Which of the following occurs when the frequency of an electromagnetic wave decreases?

The wavelength of the wave increases. "A" is false. The speed of a wave is constant at the speed of light. "B" is true. Frequency and wavelength are inversely proportional. "C" is false. Frequency does not affect a wave's amplitude.

As a blackbody is heated to higher temperatures, the wavelength of maximum energy density decreases.

True

The energy of a photon is inversely proportional to its wavelength.

True

The total energy density of blackbody radiation is directly proportional to its temperature.

True

Valence electrons are bound less tightly to the nucleus than core electrons

True. valence electrons are the outer electrons and are shielded by the core electrons. The valence electrons therefore feel a smaller effective nuclear charge than the core electrons.

Momentum

Wave character

UV rays are a type of "ionizing radiation" and are energetic enough to damage biological tissue such that they degrade into ions and electrons. What other forms of electromagnetic radiation do you think could be ionizing?

X-rays, gamma rays. X-rays and gamma rays are more energetic than UV.

What is the electron configuration of Cu⁺?

[Ar]4s¹3d⁹

The energy of a photon of light is ____ proportional to its frequency and ____ proportional to its wavelength.

directly, inversely

Without doing any calculations, which transition in the hydrogen atom has the shortest wavelength?

n = 2 -> n = 1. The transition of shortest wavelength is the highest energy transition, which is the longest arrow in the photoemission energy level diagram. The largest gap between levels occurs between n=2 and n=1.

The light emitted from one of the following hydrogen atom transitions (n = 4 → n = 3, n = 3 → n = 2, n = 2 → n = 1) causes the photoelectric effect in a metal, whereas light from the other two transitions has no effect. Which transition caused the effect?

n = 2 -> n= 1. The energy gap is largest between n=2 and n=1. This correlates to the highest energy photon being emitted.

Identify the set of quantum numbers that correspond to an electron in an s orbital.

n = 3, ℓ = 0. An s orbital by definition has to have ℓ = 0. When n = 3, this is a 3s orbital.

Identify the set of quantum numbers that correspond to an electron in a d orbital.

n = 5, ℓ = 2. A d orbital by definition has to have ℓ = 2. When n = 5, this is a 5d orbital.

Which of the following combinations of n and ℓ are not allowed?

n =2 & l = 2. According to the rules that determine ℓ, it can never equal n. The maximum allowed value of ℓ is always n − 1.

What determines the energy of an orbital for a hydrogen atom?

n.

Which combination of n and ℓ is not allowed for an electron in an atom?

n= 1, ℓ = 1. ℓ can never equal n (or be greater than) because of the rule that ℓ can equal a whole integer up to n-1.

Identify the set of quantum numbers that correspond to an electron in a p orbital.

n= 4, ℓ = 1. A p orbital by definition has to have ℓ = 1. When n = 4, this is a 4p orbital.