« Return to AACT homepage

AACT Member-Only Content

You have to be an AACT member to access this content, but good news: anyone can join!

Need Help?

Mystery Elements Mark as Favorite (25 Favorites)

ACTIVITY in Elements, Periodic Table, Atoms, Model of the Atom, Valence Electrons, Atomic Mass, Subatomic Particles. Last updated March 08, 2019.


The students will work in cooperative groups to construct Bohr models of "mystery" elements and record missing information about each element. Students will also create a new "mystery" element card for a classmate to analyze and determine its identity.

Grade Level

Middle or High School


By the end of this activity, students should be able to:

  • Correctly construct and interpret a Bohr model for an atom.
  • Describe the structure of an atom including its mass, its electrical charge, and subatomic particles.
  • Determine the quantity of electrons, protons and neutrons in an atom, given essential information.
  • Identify that protons determine an element’s identity.

Chemistry Topics

This activity supports students’ understanding of

  • Atomic Structure
  • Subatomic particles
  • Atomic Mass
  • Atomic Number


Teacher Preparation: 30 minutes

Lesson: 40 minutes


  • Activity mysteryelements materialsMetal pizza pan with 3 orbital shells and nucleus drawn on it (1 per pair of students)
  • Metal cookie sheet divided into three sections to store magnetic beads (1 per 4 students)
  • Colored magnetic beads (three colors for the three subatomic particles)
  • Laminated “Mystery” Element cards (1 set per 2 students)
  • Laminated Periodic Table (1 per 2 students)
  • Student Page
  • Index Cards (1 per student)


  • No specific safety precautions need to be observed for this activity.

Teacher Notes

  • This activity works well with four students sitting at a group table. Each student will work with a partner. Each set of partners will have one laminated periodic table, one metal pizza pan, and access to the cookie sheet with magnetic beads (shared between two sets of partners). Each student will have a student page to record their data.
  • The metal pizza pans, cookie sheets, colored beads, and magnetic strips can be purchased at a dollar store for minimal cost. The materials can be stored and reused each school year.
  • Advance Preparation includes:
    • On each metal pizza pan, use a black sharpie marker to draw a solid black circle in the middle to represent the nucleus and draw three orbital shells.
    • On each metal cookie sheet, use a black sharpie marker to divide the cookie sheet into three sections. Label one section “protons”, one section “neutrons”, and one section “electrons”.
    • Adhere a piece of adhesive magnetic strip to each colored bead.
    • Sort the colored beads onto the metal cookie sheet with one color for each of the subatomic particles.
    • Print and laminate the “mystery” element cards (1 set per 2 students).
    • Print and laminate copies of the Periodic Table of Elements.
    • Print and copy the Student Page.
  • Teachers may use the “mystery” element cards provided with this activity and/or they may make additional “mystery” element cards.
  • Student groups will work on the same set of “mystery” element cards so the teacher may assess student understanding during the activity and correct any misconceptions.

For the Student



In this activity, you are a detective trying to figure out the identity of the Mystery Elements. You will use the clues given on the Mystery Element cards, construct Bohr models of the elements, and fill out the missing information in the data table.

Pre-lab Questions

  • Vocabulary –Define the words below to beginning the activity:
  • Answer the following questions:
  • Atom
  • Subatomic particle
  • Proton
  • Neutron
  • Electron
  • Valence electron
  • Nucleus
  • Electron cloud
  • Orbital Shell
  • Bohr model
  • Atomic Number
  • Atomic Mass
  • Period
  • Group
  • What is the structure of an atom?
  • Describe the locations and charges of the subatomic particles.
  • What determines the element’s identity?
  • How is the atomic mass calculated?
  • What do groups and periods on a periodic table indicate about the atom?


Using clues to create a Bohr model of an element, determine the element’s identity, # of protons, # of neutrons, # of electrons, # of valence electrons, atomic number, atomic mass, as well as the period and group where the element is located.


  • Choose a “Mystery” Element card.
  • Use the Periodic Table to determine the identity of the element.
  • Create a Bohr model of the element using the pan and beads.
  • Complete the data section for the mystery element.
  • Complete steps 1-4 for each of the 5 “Mystery” elements.
  • Choose a new element (atomic number 1 – 18) and create a “Mystery” Element card by writing down clues on the index card.
  • Trade your index card with your partner.
  • Complete steps 2-4 for the new “Mystery” elements.
  • Answer the analysis questions.


  • What subatomic particle identifies the element?
  • How do you know which group the element is in?
  • How do you know which period the element is in?
  • How can you calculate the atomic mass?


For your closing task, write a 3-5 sentence summary about the structure of an atom, the location and charges of the subatomic particles, and what determines the identity of the element.