Problem 75 - Chemistry: The Central Science

Question

Write the condensed electron configurations for the following atoms, using the appropriate noble-gas core abbreviations: (a) Cs, (b) Ni, (c) \(\mathrm{Se}\), (d) \(\mathrm{Cd}\), (e) \(\mathrm{U}\), (f) \(\mathrm{Pb}\).

Step-by-Step Solution

Answer

The condensed electron configurations for the given atoms using noble-gas core abbreviations are as follows: (a) Cs: \([Xe] 6s^1\) (b) Ni: \([Ar] 4s^2 3d^8\) (c) Se: \([Ar] 4s^2 3d^{10} 4p^4\) (d) Cd: \([Kr] 5s^2 4d^{10}\) (e) U: \([Rn] 7s^2 5f^{3}\) (f) Pb: \([Xe] 6s^2 4f^{14} 5d^{10} 6p^2\)

Step 1: (Step 1: Find the atomic numbers)

To find the electron configurations, we need to know the atomic numbers (number of protons) of the given elements. The atomic numbers are as follows: (a) Cs (Cesium): 55 (b) Ni (Nickel): 28 (c) Se (Selenium): 34 (d) Cd (Cadmium): 48 (e) U (Uranium): 92 (f) Pb (Lead): 82

Step 2: (Step 2: Write the full electron configurations)

Using the atomic numbers, we can write the full electron configurations for the given elements: (a) Cs (Cesium): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^1\) (b) Ni (Nickel): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8\) (c) Se (Selenium): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^4\) (d) Cd (Cadmium): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10}\) (e) U (Uranium): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^6 7s^2 5f^{3}\) (f) Pb (Lead): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^2\)

Step 3: (Step 3: Determine the noble-gas core abbreviations)

We can simplify the electron configurations using the noble-gas core abbreviations: (a) Cs (Cesium): \([Xe] 6s^1\) (b) Ni (Nickel): \([Ar] 4s^2 3d^8\) (c) Se (Selenium): \([Ar] 4s^2 3d^{10} 4p^4\) (d) Cd (Cadmium): \([Kr] 5s^2 4d^{10}\) (e) U (Uranium): \([Rn] 7s^2 5f^{3}\) (f) Pb (Lead): \([Xe] 6s^2 4f^{14} 5d^{10} 6p^2\)

Key Concepts

noble-gas core

The noble-gas core is a shorthand notation for electron configurations. It lets us simplify the representation of electrons in an atom. Here's how it works:
When writing electron configurations, you start by identifying the nearest noble gas that comes before your element in the periodic table. This noble gas serves as a core representation for all the electrons it contains.

For example, cesium (Cs) can be simplified by using the electron configuration of xenon (Xe):

• The configuration of xenon is \[1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6\]
• This becomes the core for Cs, represented as \([Xe] 6s^1\)

Utilizing noble-gas cores not only saves time, but also makes configurations more concise when dealing with complex atoms.

atomic number

The atomic number is an essential property of elements. It tells us the number of protons in an atom's nucleus and determines the element's identity.
It's the blueprint for understanding how many electrons an element possesses in a neutral state.

To write an electron configuration:

• Identify the atomic number. For instance, nickel (\[ Ni \]) has an atomic number of 28.
• This tells us it has 28 electrons to arrange.

The atomic number gives us a step-by-step method to fill electron shells, crucial for understanding elements' behavior and properties.

transition metals

Transition metals are a unique category of elements located in the middle section of the periodic table. They are known for several fascinating properties:

• They have partially filled d orbitals.
• This characteristic affects their electron configurations and chemical behavior.

For example, nickel is a transition metal, and its electron configuration is written as \([Ar] 4s^2 3d^8\).

They are often involved in complex chemical reactions and are good conductors of electricity. Understanding transition metals helps in the study of chemistry and material science due to their versatile and adaptable nature.

condensed configuration

Condensed configuration helps simplify electron configurations using noble gases. This approach makes it easier to manage the otherwise lengthy strings of numbers and letters found in full configurations.
For example:

• The full electron configuration of lead is \[1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^2\]
• This can be simplified to the condensed form \([Xe] 6s^2 4f^{14} 5d^{10} 6p^2\)

This concise notation allows for easier recognition of valence electrons, which are the outermost electrons involved in chemical reactions. Condensed configurations are particularly useful when dealing with heavy elements and complex chemical equations.