Question

Draw a Lewis electron-dot symbol for each atom: (a) \(\mathrm{Rb}\) (b) Si (c) I

Short answer

(a) Rb · (b) Si: (c) I:

Step-by-step solution

Determine the number of valence electrons

Look up the position of each element on the periodic table to find the number of valence electrons. (a) \(\text{Rb}\) - Rb (Rubidium) is in Group 1. Thus, it has 1 valence electron. (b) \(\text{Si}\) - Si (Silicon) is in Group 14. Hence, it has 4 valence electrons. (c) \(\text{I}\) - I (Iodine) is in Group 17. Consequently, it has 7 valence electrons.

Draw the Lewis electron-dot symbol for each element

Using the number of valence electrons determined in Step 1, draw the Lewis dot symbols: (a) \(\text{Rb}\): Write the symbol for Rubidium (Rb) and place one dot around it to represent its 1 valence electron. \(\text{Rb}\) ·(b) Si: Write the symbol for Silicon (Si) and place four dots around it to represent its 4 valence electrons, typically arranged one dot on each side. \(\text{Si}\) : (c) I: Write the symbol for Iodine (I) and place seven dots around it to represent its 7 valence electrons. Three sides will have two dots, and one side will have one dot. \(\text{I}\) :

Key concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom. They play a crucial role in chemical bonding.
To find the number of valence electrons, you can look at the element's group number in the periodic table.
For example:

• Rubidium (Rb) is in Group 1, so it has 1 valence electron.


• Silicon (Si) is in Group 14, thus it has 4 valence electrons.


• Iodine (I) is in Group 17, giving it 7 valence electrons.

The number of valence electrons determines how an element will react and bond with others.
Understanding valence electrons helps us predict the chemical behavior of elements.

Periodic Table

The periodic table is a chart that organizes all known elements by increasing atomic number. Elements are arranged in rows (called periods) and columns (called groups or families).
Each group has elements with similar chemical properties because they have the same number of valence electrons. For instance:

• Group 1 elements all have 1 valence electron.


• Group 14 elements have 4 valence electrons.


• Group 17 elements possess 7 valence electrons.

Recognizing an element's position on the periodic table allows you to determine its valence electrons. This info is crucial for drawing Lewis dot structures and predicting chemical reactivity.

Chemical Bonding

Chemical bonding is the process by which atoms combine to form new substances. The primary types of chemical bonds are ionic and covalent bonds.

• Ionic Bonds: Formed when atoms transfer electrons. Usually occurs between metals and non-metals. For example, Rb might transfer its one valence electron to I.


• Covalent Bonds: Formed when atoms share electrons. Typically happens between non-metals, like Si and I forming bonds by sharing their valence electrons.

Understanding valence electrons and an element’s position in the periodic table helps us predict how atoms will bond chemically.
Lewis electron-dot symbols are a helpful way to visualize the valence electrons involved in chemical bonding.
These symbols show the arrangement of electrons around an element’s symbol and help us understand the basic format of molecules.