The image is a Bohr model of a sodium atom and a chlorine atom.
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:

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
Goal 2
Goal 3

Closure

Recap what has been reviewed.  

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

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