Ch.2 - Atoms, Molecules, and Ions

Brown - Chemistry: The Central Science 14th Edition

Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook

Brown 14th Edition

Ch.2 - Atoms, Molecules, and Ions

Problem 6

Chapter 2, Problem 6

The most common charge associated with selenium is 2-. Indicate the chemical formulas you would expect for compounds formed between selenium and (a) barium (b) aluminum.

Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780134414232

Verified step by step guidance

Step 1: Identify the charge of selenium. Selenium typically forms a 2- charge as an anion (Se^{2-}).

Step 2: Determine the charge of barium. Barium is an alkaline earth metal and typically forms a 2+ charge as a cation (Ba^{2+}).

Step 3: Write the chemical formula for the compound formed between selenium and barium. Since both ions have charges of equal magnitude but opposite signs, they will combine in a 1:1 ratio to form BaSe.

Step 4: Determine the charge of aluminum. Aluminum is a group 13 element and typically forms a 3+ charge as a cation (Al^{3+}).

Step 5: Write the chemical formula for the compound formed between selenium and aluminum. To balance the charges, two Al^{3+} ions will combine with three Se^{2-} ions, resulting in the formula Al_2Se_3.

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. Typically, a metal donates electrons to become a positively charged cation, while a non-metal accepts electrons to become a negatively charged anion. In this case, barium (Ba) will form a Ba²⁺ cation, and selenium (Se) will form a Se²⁻ anion, leading to the compound BaSe.

Charge Balance

In ionic compounds, the total positive charge must balance the total negative charge to achieve electrical neutrality. For barium and selenium, the Ba²⁺ cation has a +2 charge, which perfectly balances the -2 charge of the Se²⁻ anion. However, aluminum (Al) typically forms a +3 cation (Al³⁺), requiring two selenium anions to balance the charge, resulting in the formula Al2Se3.

Chemical Formulas

Chemical formulas represent the composition of a compound, indicating the types and numbers of atoms involved. The subscripts in a formula denote the ratio of each element in the compound. For the compounds formed with selenium, BaSe indicates a 1:1 ratio of barium to selenium, while Al2Se3 indicates a 2:3 ratio of aluminum to selenium, reflecting the charge balance needed for neutrality.

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