1. Lesson 24:Electron Configurations ChemCatalyst:
These drawings show two different ways to represent the arrangement of the electrons in atoms of the element calcium, Ca.
1. Name at least two differences in the drawings.
2. Name at least two similarities in the drawings.

2. Key Question
What does the periodic table indicate about the arrangements of electrons?

3. Objectives: describe electron shells and subshells in an atom
write electron configurations
explain how the periodic table shows subshells

4. Lesson 24 Notes:
a.) Electron shells (levels) are divided into subshells
Main levels are numbered (n = 1,2,3…)
The # of subshells = # of the level

5. b.) The subshells are called s, p, d, and f
s = 2 max electrons
p = 6 max electrons
d = 10 max electrons
f = 14 max electrons
c.) each subshell gets a number AND letter

6. d.) electron configuration: a shorthand way to show how electrons are arranged in atoms
The # of electrons in each subshell is written as a superscript

7. e.) first 10 elements:
If you add up the superscripts, you should get the atomic number

8. f.) The periodic table is organized in subshell blocks.

9. g. READ) To write out electron configurations, just “” from left to right, row after row
Arsenic = 1s22s22p63s23p64s23d104p3

10. Check-in 24
Identify the element with this electron configuration:
1s22s22p63s23p64s23d104p6
2. What is the electron configuration for tin (Sn)?