Activity

Using a Periodic Table to Determine Valence Electrons

The group (family) in which an element is located on the Periodic Table can be used to determine the number of valence electrons.

The Periodic Table is arranged in a manner that places elements with similar chemical properties in columns (groups).

This similarity of chemical properties is due to the fact that elements in a group have the same number of electrons in the outermost energy level (called valence electrons).  An atom’s valence electrons dictate how it will react with other atoms and molecules.  This activity underscores this fact and teaches students a simple way to determine valence electrons of elements found in Groups 1,2, and 13-18.

This activity should be completed after students have been introduced to the structure of the atom,  the Periodic Table and valence electrons. It serves as a nice warm-up activity.

Related Vocabulary:

• periodic table – an arrangement of the elements in order of their atomic numbers such that elements with similar properties fall in the same column, or group
• valence electron – an electron that is found in an atom’s outermost energy level and that determines the atom’s chemical properties.
• group – a vertical column of elements in the periodic table; elements in a group share chemical properties
• period- In chemistry, a horizontal row of elements in the periodic table
• chemical bond – an interaction that holds atoms or ions together

Materials

Note: Each student should have an atom of a different element.

Procedure

1. Gather the materials.
2. Make an atom for each students from Groups 1,2,13,14,15,16,17, or 18.                                          DON’T MAKE EXAMPLES OF ELEMENTS IN GROUPS 3-12.
3. Place a periodic table and an atom at each student’s desk.
Goal 1
• Determine valence electrons:
• Each student will begin by determining the number of valence electrons in his/her atom.  Give students enough time and provide more information if necessary.  If students have forgotten that the valence electrons are on the outermost level, remind them of this fact.
• Have each student indicate how many valence electrons are on the atom he/she was given.  Discuss valence electrons briefly.
Goal 2
• Find the element on the Periodic Table
• Tell students that the atoms they are being given are neutral atoms (meaning they have the same number of electrons as protons).  Have the students find the elements on the Periodic table.  Guide them if necessary.
Goal 3
• Determine pattern for Groups on the periodic table
• After the students find their elements, have them determine which group the atom is in.
• Ask students to try to find a correlation between the number of valence electrons and the group number.

Closure

Recap what has been reviewed.

• Valence electrons are on the outermost energy level.
• Neutral atoms will have equal numbers of protons and electrons.
• Clearly explain to the students that elements in Groups 1,2, and 13-18 will have valence electrons as follows:

Group 1 and 2 – Same number of valence electrons as the group number

Group 13-18 – Same number of valence electrons as the last digit of the group number

NGSS Standards:

High School PS1.A: Structure and Properties of Matter
The Periodic Table orders elements horizontally by the number of protons in the atoms’ nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron state. (HS-PS1-1)

By Laura Hospitál