Question

Using only the periodic table, write the symbol of the ion most typically formed by each of the following elements: a. K d. Cl b. Ca e. Ba c. S f. Br

Short answer

K -> K^+, Ca -> Ca^{2+}, S -> S^{2-}, Cl -> Cl^-, Ba -> Ba^{2+}, Br -> Br^-

Step-by-step solution

Identify the Element

Locate the element on the periodic table to determine its group number and valence electrons.

Determine Tendency to Gain or Lose Electrons

Based on the group number, determine if the element tends to lose or gain electrons to achieve a stable, noble gas electron configuration.

Write the Ion Symbol for Each Element

Using the information from Step 2, write the symbol for the ion formed. Include the charge as a superscript.

Key concepts

Element Ion Formation

Elements form ions to achieve a stable electron configuration. This usually means having the same number of electrons as the nearest noble gas. When they lose or gain electrons, they form ions.

For example:

• Potassium (K) loses one electron to form a K⁺ ion.
• Calcium (Ca) loses two electrons to form a Ca²⁺ ion.
• Chlorine (Cl) gains one electron to form a Cl^- ion.

The periodic table helps predict these changes. Elements on the left (metals) tend to lose electrons, while elements on the right (nonmetals) tend to gain them.

Valence Electrons

Valence electrons are the outermost electrons of an atom. They are crucial in determining how an element reacts chemically. For example, potassium (K) is in group 1 and has one valence electron.

• Elements in Group 1 have 1 valence electron.
• Elements in Group 2 have 2 valence electrons.
• Elements in Group 17 have 7 valence electrons and tend to gain one to complete their outer shell.

By knowing the number of valence electrons, you can predict an element's chemical behavior and the type of ion it will form.

Noble Gas Electron Configuration

Noble gases have a complete outer electron shell, making them very stable. This is the electron configuration that other elements strive to achieve when they form ions.

• For example, potassium (K) will lose one electron to match the electron configuration of argon (Ar).
• Calcium (Ca) loses two electrons to achieve the same configuration.
• Chlorine (Cl) gains one electron to achieve the electron configuration of argon (Ar).

The goal for atoms in forming ions is to achieve this stable, noble gas-like electron configuration.