Electron Detectives
A neutral atom has the ground-state configuration [Ar] 4s² 3d¹⁰ 4p³. How many orbitals contain at least one electron? Include the orbitals represented by [Ar].
There are 18 occupied orbitals
A neutral atom has 2, 8, 8, 2 electrons in successive principal energy levels. A student incorrectly models its 2+ ion as 2, 8, 6, 2. What should the ion’s electron distribution be?
2, 8, 8.
Three neutral atoms are plotted on a graph with:
-Atom A is in period 3, group 14.
-Atom B is in period 3, group 16.
-Atom C is in period 4, group 14.
Using periodic trends, which atom belongs farthest toward the upper left of the graph?
B
Each photon in beam B has 3/2 as much energy as a photon in beam A. Both beams travel through a vacuum. What is the wavelength ratio λᵦ/λₐ?
2/3
An unknown sample contains exactly one of these hypothetical elements which have wavelengths given below:
A: 420, 510, 670 nm
B: 420, 560, 670 nm
C: 450, 510, 730 nm
A detector initially records only 400–500 nm and detects a line at 420 nm. Every listed line within its range is detectable. What one additional wavelength could you check, after extending the detector’s range, to distinguish the remaining possibilities?
510 nm or 560 nm.
A student writes gallium’s configuration as [Ar] 4s² 4p¹. Write the corrected noble-gas configuration.
[Ar] 4s² 3d¹⁰ 4p¹.
X²⁺ and Y³⁻ each contain 36 electrons. Write the actual chemical symbol and charge of the larger ion.
As³⁻
Three neutral atoms have these ground-state electron distributions:
A has 2, 8, 1
B has 2, 8, 7
C has 2, 8, 8, 1
Rank them from lowest to highest first ionization energy.
C < A < B.
A photon has an energy of 3.10 × 10⁻¹⁹ J. Calculate its wavelength in nanometers.
641 nm
A gas’s emission lines become brighter, but their wavelengths stay the same. What happens to the energy of each photon: increases, decreases, or stays the same?
Stays the same.
A nitrogen atom starts with the configuration 1s² 2s² 2p³. One 2p electron absorbs energy and moves into an empty 3s orbital. How many unpaired electrons does the atom now have?
3
Rank Al³⁺, S, and S²⁻ from smallest to largest radius.
Al³⁺ < S < S²⁻.
Element M has 27 protons and an average atomic mass of 58.93 u. Element N has 28 protons and an average atomic mass of 58.69 u. Which comes first in the modern periodic table?
M
Beam A has a frequency of 6.00 × 10¹⁴ Hz. Beam B has a wavelength of 7.50 × 10² nm. Calculate the ratio of their photon energies, Eₐ/Eᵦ.
1.50
A model atom has these energy levels:
U: 5.0 × 10⁻¹⁹ J
M: 2.0 × 10⁻¹⁹ J
G: 0 J
All downward transitions are allowed. Rank the three transitions from longest to shortest emitted wavelength.
M → G
U → M
U → G.
Two models each place five electrons in a 3d sublevel:
How many more unpaired electrons does Model A have than Model B?
4 more.
A particle has 12 protons and an electron distribution of 2, 7, 3. Classify it as a ground-state neutral atom, an excited neutral atom, a positive ion, or a negative ion.
An excited neutral atom.
Helium and beryllium each have two electrons in their highest occupied principal energy level. Which has a completely filled outermost principal energy level?
Helium.
Exactly one value in this report has a power-of-ten error. Give only the corrected value with its unit.
Use 1 μm = 10⁻⁶ m and 1 MHz = 10⁶ Hz.
3.98 × 10⁻¹⁹ J
A model atom has these allowed energy levels:
Which transition could absorb a photon with an energy of 2.50 × 10⁻¹⁹ J?
M → U
Which two period-4 elements have exactly two unpaired electrons in their neutral ground-state atoms and no partially filled d sublevel?
Germanium and selenium.
A neutral atom has the ground-state electron configuration [Ar] 4s² 3d¹⁰ 4p⁴.
Name a different element expected to have similar chemical properties.
Oxygen, sulfur, tellurium, or polonium.
Choose a pair of period-2 elements, excluding neon. The second element must have exactly three more valence electrons, a smaller atomic radius, a higher first ionization energy, and a higher electronegativity than the first. Give only the two symbols in order.
Li, C
Be, N
B, O
C, F.
A model atom releases the same total energy either as one photon with a wavelength of 3.60 × 10² nm or as two photons. In the two-photon route, the first photon has a wavelength of 6.00 × 10² nm. What is the second photon’s wavelength, in nm?
9.00 × 10² nm
A model atom has energy levels at 0 J, 2.0 × 10⁻¹⁹ J, and 4.0 × 10⁻¹⁹ J. Every downward transition is allowed. How many distinct emission wavelengths are possible?
2