Chemistry: Quantum Mechanical Model of the Atom Worksheet

Question 1

Describe how the quantum mechanical model of the atom is different from the Bohr model of the atom.

Accepted Answer

The Bohr model places electrons in fixed circular paths around the nucleus, while the quantum mechanical model describes electrons as existing in orbitals, which are regions of high probability where an electron may be found.

Question 2

In the quantum mechanical model, what is an orbital?

Accepted Answer

An orbital is a three-dimensional region around the nucleus where there is a high probability of finding an electron.

Question 3

Explain why the word probability is important when describing the location of an electron.

Accepted Answer

Probability is important because the exact position of an electron cannot be known at all times. The quantum mechanical model predicts where an electron is most likely to be found.

Question 4

Identify the four types of atomic orbitals commonly used in high school chemistry and give the maximum number of electrons each sublevel can hold.

Accepted Answer

The common sublevels are s, p, d, and f. The s sublevel holds 2 electrons, the p sublevel holds 6 electrons, the d sublevel holds 10 electrons, and the f sublevel holds 14 electrons.

Question 5

A student says, "An electron in a 3p orbital is in the third main energy level." Explain whether the student is correct.

Accepted Answer

The student is correct because the number 3 in 3p represents the principal energy level, also called the main energy level.

Question 6

For the orbital label 4d, identify the principal energy level and the sublevel.

Accepted Answer

In the label 4d, the principal energy level is 4 and the sublevel is d.

Question 7

Complete the electron configuration for carbon, which has 6 electrons.

Accepted Answer

The electron configuration for carbon is 1s^2 2s^2 2p^2. This accounts for all 6 electrons.

Question 8

Write the electron configuration for sodium, which has 11 electrons.

Accepted Answer

The electron configuration for sodium is 1s^2 2s^2 2p^6 3s^1. This shows that sodium has one electron in the 3s orbital.

Question 9

Use the Aufbau principle to explain why the 4s sublevel is filled before the 3d sublevel in many electron configurations.

Accepted Answer

The Aufbau principle states that electrons fill the lowest available energy orbitals first. In many atoms, the 4s sublevel is lower in energy than the 3d sublevel, so 4s fills first.

Question 10

State Hund's rule and apply it to the three 2p orbitals when carbon has two electrons in 2p.

Accepted Answer

Hund's rule says that electrons occupy equal-energy orbitals one at a time with the same spin before pairing. For carbon, the two 2p electrons go into two separate 2p orbitals before pairing in one orbital.

Question 11

State the Pauli exclusion principle and explain what it means for one orbital.

Accepted Answer

The Pauli exclusion principle states that an orbital can hold at most two electrons, and those two electrons must have opposite spins.

Question 12

An orbital box diagram shows one box with two arrows both pointing up. Explain what is wrong with this diagram.

Accepted Answer

The diagram is incorrect because two electrons in the same orbital must have opposite spins. The arrows should point in opposite directions.

Question 13

Explain how an atomic emission spectrum provides evidence that electrons have quantized energy levels.

Accepted Answer

An atomic emission spectrum shows only specific colors or wavelengths of light. This means electrons can only lose certain amounts of energy as they move from higher energy levels to lower energy levels, so their energy levels are quantized.

Question 14

A photon has an energy of 3.20 x 10^-19 joules. Use E = hν, with h = 6.63 x 10^-34 J·s, to calculate the frequency of the photon.

Accepted Answer

The frequency is found using ν = E ÷ h. ν = (3.20 x 10^-19 J) ÷ (6.63 x 10^-34 J·s) = 4.83 x 10^14 Hz.

Question 15

Explain why the quantum mechanical model is more useful than the Bohr model for describing atoms with many electrons.

Accepted Answer

The quantum mechanical model is more useful because it describes electrons in orbitals with different shapes and energies, and it accounts for electron behavior in atoms with more than one electron. The Bohr model works best as a simple model for hydrogen but does not accurately describe many-electron atoms.

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Chemistry: Quantum Mechanical Model of the Atom

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