Question

Write the noble-gas notation for the electron configurations of each of the following elements: a. Hf d. At b. Sc e. Ac c. Fe f. Zn

Short answer

a. [Xe] 6s^2 4f^14 5d^2b. [Ar] 3d^1 4s^2c. [Ar] 3d^6 4s^2d. [Xe] 4f^14 5d^10 6s^2 6p^5e. [Rn] 6d^1 7s^2f. [Ne] 3d^10 4s^2

Step-by-step solution

- Understanding Noble-Gas Notation

Noble-gas notation involves writing the electron configuration starting from the nearest noble gas element with fewer electrons than the element in question. The noble gas is placed in brackets.

- Finding the Noble Gas for Each Element

Identify the noble gas that comes before each element on the periodic table.a. Hf: Xenon (Xe)b. Sc: Argon (Ar)c. Fe: Argon (Ar)d. At: Xenon (Xe)e. Ac: Radon (Rn)f. Zn: Neon (Ne)

- Writing Electron Configurations

For each element, write the electron configuration starting from the identified noble gas.a. Hf: [Xe] 6s^2 4f^14 5d^2b. Sc: [Ar] 3d^1 4s^2c. Fe: [Ar] 3d^6 4s^2d. At: [Xe] 4f^14 5d^10 6s^2 6p^5e. Ac: [Rn] 6d^1 7s^2f. Zn: [Ne] 3d^10 4s^2

Key concepts

Electron Configuration

Electron configuration is the arrangement of electrons in an atom’s electron shells and subshells. Electrons fill these shells and subshells in a specific order, following Hund's rule, the Pauli Exclusion Principle, and the Aufbau Principle. The order is typically from lower to higher energy levels. For example, electrons fill the 1s subshell before the 2s subshell. This pattern helps in predicting chemical bonding and properties.

Key points to remember:

• Electrons fill the lowest available energy levels first (Aufbau Principle).
• Only two electrons can occupy the same orbital (Pauli Exclusion Principle).
• Electrons fill degenerate orbitals singly before pairing (Hund's Rule).

Noble Gas

Noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These are located in Group 18 of the periodic table. They have fully filled valence shells, making them very stable and unreactive. When writing electron configurations using noble-gas notation, the noble gas in the previous period (row) is used as a shorthand to simplify the configuration.

Noble-gas notation is convenient because:

• It simplifies long electron configurations.
• It highlights the electrons involved in chemical bonding (valence electrons).
• It helps quickly identify the core and valence electrons of an element.

For example, the electron configuration of iron (Fe) can be written in long form as 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6, but using noble-gas notation, it becomes [Ar] 4s^2 3d^6.

Periodic Table

The periodic table arranges elements in increasing atomic number and groups them based on similar chemical properties. Elements are organized into periods (rows) and groups (columns). The position of an element on the table gives crucial information about its electron configuration.
The main areas of the periodic table are:

• S-block (groups 1-2): These have their outermost electrons in s orbitals.
• P-block (groups 13-18): These elements have their outermost electrons in p orbitals.
• D-block (transition metals): These have their outermost electrons in d orbitals.
• F-block (lanthanides and actinides): These have their outermost electrons in f orbitals.

Using the periodic table, you can determine electron configurations and simplify them using noble-gas notation. For example, for hafnium (Hf), the nearest noble gas is xenon (Xe), so its configuration is written as [Xe] 6s^2 4f^14 5d^2.