Periodic Table Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Periodic Table.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A systematic arrangement of all known chemical elements organized by increasing atomic number into rows (periods) and columns (groups), where elements in the same group.

A map of all elements organized so similar ones are in the same column.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Elements in the same group have the same number of valence electrons.

Common stuck point: Rows (periods) = number of electron shells. Columns (groups) = valence electrons.

Sense of Study hint: When using the periodic table, read both rows and columns. First note that rows (periods) indicate the number of electron shells. Then note that columns (groups) indicate the number of valence electrons for main-group elements. Finally, use position to predict properties: metals on the left, nonmetals on the right, metalloids along the staircase.

Worked Examples

Example 1

easy
Using the periodic table, predict whether silicon (Si) is a metal, nonmetal, or metalloid. Justify your answer.

Solution

  1. 1
    Silicon is in Group 14, Period 3, located along the staircase line (zigzag) dividing metals from nonmetals.
  2. 2
    Elements along this boundary are typically metalloids.
  3. 3
    Silicon exhibits properties of both metals and nonmetals: it has a metallic luster but is a poor conductor (semiconductor).

Answer

\text{Silicon is a metalloid.}
The periodic table's organization allows us to predict properties based on an element's position. Metalloids lie along the metal-nonmetal boundary and have intermediate properties.

Example 2

medium
Arrange the following elements in order of increasing atomic radius: \text{Na}, \text{Mg}, \text{K}, \text{Al}.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Which group of the periodic table contains the noble gases? Why are they chemically inert?

Example 2

medium
An element is in Group 17 and Period 3 of the periodic table. What do the group and period tell you about its electrons?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

elementvalence electron