‘Write the abbreviated electron configurations of the following elements: 6) iridium 7) chlorine 8) nobelium 9) caesium 10) magnesium’
The Correct Answer and Explanation is:
Here are the abbreviated electron configurations for the given elements:
- Iridium (Ir): [Xe] 4f¹⁴ 5d⁷ 6s²
- Chlorine (Cl): [Ne] 3s² 3p⁵
- Nobelium (No): [Rn] 5f¹⁴ 7s²
- Caesium (Cs): [Xe] 6s¹
- Magnesium (Mg): [Ne] 3s²
Explanation:
Electron configurations represent the distribution of electrons among the orbitals of an atom. Abbreviated (or noble gas) electron configurations simplify this process by using the symbol of the nearest noble gas with a lower atomic number, enclosed in brackets, to represent the core electrons. This method highlights the valence electrons, which are most important in chemical reactions.
Iridium (Ir), atomic number 77: The nearest noble gas is xenon (Xe), atomic number 54. After xenon, 14 electrons fill the 4f orbitals, 9 fill the 5d and 6s orbitals. Iridium has a partially filled 5d orbital, with the configuration [Xe] 4f¹⁴ 5d⁷ 6s², consistent with transition metal behavior.
Chlorine (Cl), atomic number 17: Neon (Ne) is the nearest noble gas. After neon, seven more electrons fill the 3s and 3p orbitals. Chlorine’s configuration [Ne] 3s² 3p⁵ shows seven valence electrons, making it one electron short of a full octet, explaining its high reactivity.
Nobelium (No), atomic number 102: With radon (Rn) as the previous noble gas, the next 14 electrons occupy the 5f orbitals, completing them. The configuration [Rn] 5f¹⁴ 7s² indicates Nobelium’s placement in the actinide series with a full 5f subshell.
Caesium (Cs), atomic number 55: After xenon, one electron enters the 6s orbital. Its configuration [Xe] 6s¹ indicates a single valence electron, making caesium highly reactive and typical of alkali metals.
Magnesium (Mg), atomic number 12: Neon precedes it. Two additional electrons occupy the 3s orbital. The configuration [Ne] 3s² shows a full s orbital, explaining its relatively low reactivity among alkaline earth metals.
