Ch.7 - Covalent Bonding and Electron-Dot Structures

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.7 - Covalent Bonding and Electron-Dot Structures

Problem 80

Chapter 7, Problem 80

Calculate the energy change in kilojoules per mole when lithium atoms lose an electron to bromine atoms to form isolated Li+ and Br-ions. [The Ei for Li1g2 is 520 kJ/mol; the Eea for Br1g2 is -325 kJ/mol.] Will a lithium atom transfer an elec-tron to a bromine atom to form isolated Li+ 1g2 and Br-1g2 ions? Explain.

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Identify the given values: Ionization energy (Ei) for Li is 520 kJ/mol and electron affinity (Eea) for Br is -325 kJ/mol.

Understand that the ionization energy is the energy required to remove an electron from a neutral atom, while electron affinity is the energy change when an electron is added to a neutral atom.

Calculate the total energy change for the process by adding the ionization energy of lithium and the electron affinity of bromine: Total energy change = Ei (Li) + Eea (Br).

Substitute the given values into the equation: Total energy change = 520 kJ/mol + (-325 kJ/mol).

Determine if the process is energetically favorable: If the total energy change is negative, the process is favorable, indicating that a lithium atom will transfer an electron to a bromine atom to form isolated ions.

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Key Concepts

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

Ionization Energy (Ei)

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. For lithium, the given ionization energy of 520 kJ/mol indicates the energy needed to convert a neutral lithium atom into a lithium ion (Li+). This process is endothermic, meaning it absorbs energy, which is crucial for understanding the energy dynamics when lithium loses an electron.

Electron Affinity (Eea)

Electron affinity refers to the energy change that occurs when an electron is added to a neutral atom in the gaseous state. For bromine, the electron affinity of -325 kJ/mol signifies that energy is released when a bromine atom gains an electron to form a bromide ion (Br-). This exothermic process is important for evaluating the overall energy change when lithium and bromine interact.

Energy Change Calculation

To determine whether lithium will transfer an electron to bromine, we calculate the total energy change by combining the ionization energy of lithium and the electron affinity of bromine. The overall energy change is given by ΔE = Ei + Eea. If this value is negative, it indicates that the process is energetically favorable, suggesting that lithium will indeed transfer an electron to bromine to form Li+ and Br- ions.

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