Question

Use the periodic table, but not Table \(2.2,\) to write the symbols for ions of (a) barium, (b) oxygen, (c) fluorine, (d) strontium, and (e) rubidium.

Short answer

The symbols for the ions of the elements are: (a) Ba^2+, (b) O^2-, (c) F^-, (d) Sr^2+, (e) Rb^+.

Step-by-step solution

Determine the Number of Valence Electrons for Each Element

Look up each element on the periodic table to find the number of valence electrons. Barium (Ba) is in Group 2 and has 2 valence electrons. Oxygen (O) is in Group 16 and has 6 valence electrons. Fluorine (F) is in Group 17 and has 7 valence electrons. Strontium (Sr) is also in Group 2 and has 2 valence electrons. Rubidium (Rb) is in Group 1 and has 1 valence electron.

Determine the Charge of the Ions

Based on their positions in the periodic table: Barium will lose 2 electrons to form a Ba^2+ ion. Oxygen will gain 2 electrons to become O^2-. Fluorine will gain 1 electron to become F^-. Strontium loses 2 electrons to become Sr^2+. Rubidium loses 1 electron to form Rb^+.

Write the Symbols for the Ions

Now write the symbols for each ion with the correct charge. Barium ion would be represented as Ba^2+, oxygen ion as O^2-, fluorine ion as F^-, strontium ion as Sr^2+, and rubidium ion as Rb^+.

Key concepts

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom. These electrons play a critical role in chemical reactions because they can be lost, gained, or shared to form chemical bonds. For example, barium (Ba) has two valence electrons, which it can lose to become more stable, forming a Ba²⁺ ion. Similarly, oxygen with six valence electrons tends to gain two electrons to achieve a stable electron configuration akin to the noble gases. The number of valence electrons is typically determined by an element's group number in the periodic table; for Groups 1 and 2, the group number equals the number of valence electrons, while for Groups 13 to 18, the number of valence electrons is the group number minus 10.

Understanding valence electrons is fundamental in predicting how atoms will interact and what ions they will form. These outer electrons dictate not only the charge of the resulting ion, but also the nature of the bonds an element will prefer, whether ionic or covalent.

Ion Charge

An ion's charge is a fundamental property that arises when an atom gains or loses electrons. Atoms seek to either fill or empty their outer electron shell to achieve a stable electron configuration, and in doing so, they become ions. For instance, rubidium (Rb) loses one electron and becomes a positively charged ion, Rb⁺. On the other hand, fluorine (F) tends to gain one electron to achieve stability, resulting in a fluoride ion, F^-.

The charge of an ion is often predictable based on its position in the periodic table. Elements in Group 1 typically form +1 ions, while those in Group 17 usually form -1 ions. Ion charge is critical for understanding chemical formulas and reactions because it determines how ions will combine to create compounds. The balance between positive and negative charges in ionic compounds is essential for their stability. When writing chemical symbols for ions, it's important to include the ion charge to accurately convey the ionic species.

Chemical Symbols

Chemical symbols are shorthand representations of elements and ions using letters and numbers. Each element has a unique one- or two-letter symbol, such as Ba for barium or O for oxygen. Ions are represented by their element's symbol with a subscript indicating the charge, for example, Ba²⁺ and O^2-. These symbols provide a universal language for scientists around the world to communicate chemical information succinctly and accurately.

Knowing how to write chemical symbols for ions requires an understanding of the ion's charge. The charge is indicated as a superscript following the element symbol. For example, strontium forms an ion with a 2+ charge, denoted as Sr²⁺. These symbolic notations are crucial for writing chemical equations and understanding how ions interact to form ionic compounds. The precision in chemical symbols allows for clear and concise communication within the scientific community and is foundational in the study and practice of chemistry.