General Chemistry

General Questions

The electron configuration of an atom describes the distribution of electrons in atomic orbitals. For gold (Au), which is a transition metal with atomic number 79, we will determine its electron configuration by following the Aufbau principle, Hund's rule, and the Pauli exclusion principle. These rules help us fill the atomic orbitals with electrons in the correct order. Step 1: Identify the Atomic Number The atomic number of gold (Au) is 79, which means a neutral gold atom has 79 electrons. Step 2: Use the Aufbau Principle The Aufbau principle states that electrons fill atomic orbitals starting with the lowest energy level before filling higher levels. The order in which orbitals are filled is based on their increasing energy and is often remembered using the "n + l rule" or by referring to an Aufbau diagram. Step 3: Follow the Orbital Filling Sequence The sequence in which orbitals are filled is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. For gold, we will fill up to the 6s and 5d orbitals. Step 4: Apply Hund's Rule and the Pauli Exclusion Principle Hund's rule states that electrons will fill an unoccupied orbital before they pair up in an occupied one. The Pauli exclusion principle states that no two electrons can have the same set of four quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins. Step 5: Fill the Orbitals with Electrons Starting with the 1s orbital, we fill each orbital with the maximum number of electrons it can hold (2 for s orbitals, 6 for p orbitals, 10 for d orbitals, and 14 for f orbitals) until we have used all 79 electrons. The electron configuration for gold (Au) is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹ 4f¹⁴ 5d¹⁰ Step 6: Consider Electron Configuration Shorthand To write the electron configuration in shorthand, we use the noble gas preceding gold in the periodic table to represent the filled orbitals up to that point. The noble gas before gold is xenon (Xe), which has an atomic number of 54. The shorthand electron configuration for gold (Au) starts with [Xe], then we add the remaining orbitals that are filled after xenon: [Xe] 6s¹ 4f¹⁴ 5d¹⁰ This shorthand notation shows that gold has the same electron configuration as xenon plus the electrons in the 6s, 4f, and 5d orbitals. In summary, the electron configuration of gold (Au) is [Xe] 6s¹ 4f¹⁴ 5d¹⁰, which reflects the distribution of 79 electrons in the atomic orbitals.

Question

What is the electron configuration of gold (Au)?

Solution

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