Valence Electrons and Trends in the Periodic Table
This instructor led activity will produce a partially filled periodic table that contains electron-dot models for the first twenty elements in the appropriate boxes. It will be used as a visual tool for students to connect concepts such as valence electrons and group properties, atomic radius trends, ionic and covalent bonding regions and others.
Students should see relationships between numbers of valence electrons and properties of elements.
When placing electrons around the element symbols students will notice that all p-sublevels are being half-filled before any one p-sublevel is completely filled.
Using the concept of proton-electron attractions students will see trends of atomic radius across rows (series) of the periodic table.
Students will discover trends of ion charges with relation to the periodic table.
Students should be familiar with the following terms: valence electrons, electron-dot model, physical properties, chemical properties, columns, rows, periods, series, atom and ion.
Students use models to visualize atoms.
The periodic table displays several trends that helps understand concepts in chemistry.
Electron-dot models are one type of model used to help understand atoms.
Context for Use
Resource Type: Activities:Classroom Activity
Grade Level: High School (9-12)
Description and Teaching Materials
In this short activity (20-25 minutes) students will be provided a blank periodic table and will fill in the electron-dot model for the first twenty elements. It maybe helpful to have students number the boxes one through twenty (atomic numbers) in the lower left corner first to avoid confusion. Adding the atomic numbers in the lower corner allows for the addition of mass numbers or atomic weights later if desired.
It is very helpful to model a couple of electron-dot examples to get students started. Use the generic model:
Where X is the symbol of the element and accounts for the nucleus and all the filled inner shell electrons. The valence electrons are symbolized as a dot and placed in increasing number around the symbol.
Even though the numbering scheme is no longer widely used it will be helpful later when introducing the idea of half-filled S and P sub-orbital's.
Have students keep their tables for a reference tool.
Teaching Notes and Tips
This activity has students place the electron-dot model in each appropriate box, but if boxes are large enough other information maybe added throughout the year. Information that could be included, but is not limited to, are element name, atomic numbers, mass numbers or weights, common oxidation numbers.
At some point the columns could be lightly shaded and a legend could be added. This works best when either all the information is on the table or when discussing properties.
Have students reference their tables when introducing concepts like atomic and ionic radius trends, ionic and covalent bonding regions.
Have students add information to the back of their tables like polyatomic ions, equations, key concepts, exceptions to rules. It helps them learn it better than reading it off another chart and it gives them ownership so they keep them longer.
This activity can stand alone or be used with the attached worksheet and/or create other worksheets when discussing atom radius or ion radius...
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