Chemistry Topic
Electronic Configuration
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- Flashcards
- Quiz
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Study focus - 3 things
- Electronic configuration shows how electrons are arranged in shells
- For the first 20 elements, shells fill in a simple 2, 8, 8 pattern for Grade 9 work
- Outer-shell electrons help explain groups and bonding
Section 1What it means
Electronic configuration is a way to show where electrons are placed around an atom. The electrons go into shells. In plain words, it is the atom's electron address.
Section 2Simple shell filling
For early Grade 9 chemistry, the first shell holds up to 2 electrons. The second and third shells are commonly treated as holding up to 8 for the first 20 elements. Always follow the pattern your teacher uses in class.
Section 3Outer shell
The outer shell is the last shell with electrons in it. These electrons are called valence electrons. They matter because they help decide how atoms bond.
Section 4Groups link to outer electrons
For many main-group elements, the group number helps show how many outer-shell electrons the atom has. Watch out: helium is a special case with a full first shell of 2.
Examples
Magnesium has 12 electrons. Write its simple electronic configuration.
Fill shells as 2, then 8, then the remaining 2. Magnesium is 2,8,2.
Chlorine has electronic configuration 2,8,7. How many outer-shell electrons does it have?
It has 7 outer-shell electrons. The last number in the configuration shows the electrons in the outer shell.
Now let's water it
Session runs notes to flashcards to quiz back-to-back.