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Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory
Chapter 6, Problem 101

Heating elemental cesium and platinum together for two days at 973 K gives a dark red ionic compound that is 57.67% Cs and 42.33% Pt. (c) What are the charge and electron configuration of the platinum ion?

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1. First, we need to determine the empirical formula of the compound. The empirical formula is the simplest, most reduced ratio of elements in a compound. To do this, we assume we have 100 g of the compound. This means we have 57.67 g of Cs and 42.33 g of Pt. We then convert these masses to moles using the atomic masses of Cs and Pt.
2. After converting to moles, we find the ratio of moles of Cs to Pt by dividing each by the smallest number of moles calculated. This gives us the empirical formula.
3. The empirical formula tells us the ratio of Cs to Pt in the compound. Since Cs is in group 1 and always forms +1 ions, the charge on the Pt ion must be such that the overall charge of the compound is zero. For example, if the empirical formula is Cs2Pt, then the charge on Pt must be -2 to balance the +2 charge from the two Cs+ ions.
4. Once we know the charge on the Pt ion, we can determine its electron configuration. The electron configuration of a neutral Pt atom is [Xe] 4f14 5d9 6s1. When Pt loses electrons to form a cation, it loses them from the highest energy level first. In this case, that would be the 6s orbital, then the 5d orbital.
5. Subtract the number of electrons equal to the charge on the Pt ion from the electron configuration to get the electron configuration of the Pt ion.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons, resulting in the formation of charged ions. In this case, cesium (Cs) donates an electron to platinum (Pt), leading to the creation of a positively charged cesium ion (Cs+) and a negatively charged platinum ion (Pt2+). Understanding the formation of ionic compounds is crucial for determining the charge of the ions involved.
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Oxidation States

The oxidation state of an element in a compound indicates the degree of oxidation (loss of electrons) or reduction (gain of electrons) it has undergone. In this scenario, platinum typically exhibits a +2 oxidation state when forming ionic compounds, which is essential for identifying the charge of the platinum ion in the compound formed with cesium.
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Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For platinum, the electron configuration is [Xe] 4f14 5d9 6s1. When platinum loses two electrons to form the Pt2+ ion, its electron configuration changes to [Xe] 4f14 5d8, reflecting the removal of electrons from the outermost orbitals, which is important for understanding its chemical behavior and properties.
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