Problem 115 - Chemistry The Molecular Science

Question

Suppose a new clement, unbinilium, has recently becn discovered. Its atomic number is 120 . (a) Write the electron configuration of the element. (b) Name another element you would expect to find in the same periodic table group as unhinilium. (c) Write the formulas for the compounds of unbinilium with \(\mathrm{O}\) and \(\mathrm{Cl}\). Use \(\mathrm{X}\) for the chemical symbol.

Step-by-Step Solution

Answer

(a) [Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{6} 8s^{2}; (b) Barium (Ba); (c) XO and XCl₂.

Step 1: Understand the Element's Atomic Number

Unbinilium has an atomic number of 120, which means it has 120 protons and, in a neutral state, 120 electrons.

Step 2: Determine the Electron Configuration

Remember that the electron configuration follows the order of filling orbitals: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. For atomic number 120: - The first 118 electrons fill up to 7p6 (with the electron configuration: \([Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{6}\)).- We then need to continue with: \(8s^2\) to account for electrons 119 and 120. Thus, the electron configuration of unbinilium is \([Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{6} 8s^{2}\).

Step 3: Identify the Element's Group

Elements with similar electron configurations in their outermost shells are placed in the same group. Unbinilium's outermost electrons are in the 8s orbital, indicating it belongs to Group 2 (alkaline earth metals) of the periodic table.

Step 4: Select a Similar Element

Based on its group, an element in the same group as Unbinilium (Group 2) is Barium (Ba), which shares similar outer electron configurations.

Step 5: Formulate Compound with Oxygen

Group 2 elements typically form +2 oxidation states, combining with oxygen (which typically forms a -2 oxidation state) to create the simplest compound in the ratio of 1:1. Therefore, the formula for X with oxygen (O) is XO.

Step 6: Formulate Compound with Chlorine

Similar to oxygen, chlorides of Group 2 elements typically reflect the +2 oxidation state of unbinilium. Chlorine generally forms a -1 oxidation state, requiring two chloride ions to neutralize one X ion. Thus, the compound formed is XCl₂.

Key Concepts

Electron Configuration

Electron configuration is the arrangement of electrons in an atom's orbitals. For elements, it follows a specific order, known as the Aufbau principle, which states that electrons fill orbitals starting at the lowest energy level before filling higher levels. For unbinilium, with an atomic number of 120, this means it has 120 electrons when neutral, which fill the orbitals in a specific sequence. The completed electron configuration up to element 118 (oganesson) is \[\text{[Rn]} 5f^{14} 6d^{10} 7s^{2} 7p^{6}\].When considering unbinilium, we continue with two more electrons, filling the next orbital in sequence, the 8s orbital, thus resulting in \[\text{[Rn]} 5f^{14} 6d^{10} 7s^{2} 7p^{6} 8s^{2}.\] This configuration highlights that unbinilium's outermost electrons reside in the 8s orbital.

Periodic Table Groups

Periodic table groups are columns on the periodic table, and they represent elements with similar properties and electron configurations in their outermost shells. There are 18 groups in total, and elements in each group exhibit similar chemical behaviors. Unbinilium's electron configuration suggests its outer electrons are in the 8s orbital. This characteristic places it in Group 2, known as the alkaline earth metals. Group 2 elements typically have two electrons in their outer shell, leading to similar reactivity and properties among them. An element like barium (Ba) is also found in Group 2. It shares a similar electron arrangement, with its outer electrons residing in the 6s orbital. Therefore, such elements are expected to exhibit similar chemical properties and reactivity, particularly in forming compounds.

Compound Formulas

Formulating compounds involves understanding the oxidation states of elements and how they combine to form neutral molecules. For alkaline earth metals, such as those in Group 2, the typical oxidation state is +2. This means these elements will lose two electrons when forming compounds, often resulting in very predictable compound formulas.For instance, when combining unbinilium (X) with oxygen (O), which typically has a -2 oxidation state, they form a compound in a 1:1 ratio since +2 from unbinilium balances with -2 from oxygen. This leads to the chemical formula being simply \[ XO. \] On the other hand, unbinilium with chlorine (Cl), which has a -1 oxidation state, requires two chloride ions to balance out unbinilium's +2 charge, resulting in the formula \[ XCl_2. \] This method of balancing charges to achieve neutral compounds is a fundamental aspect of understanding compound formulas in chemistry.