Without your notes: write the electron arrangement, then the number of core and valence electrons.
L02.1 Build & Discover
Lithium · Z = 3 · neutral
Lesson 3 · Building the Bohr model
No notes — answer from memory, even if you have to guess. Retrieving is what makes it stick.
Without your notes: write the electron arrangement, then the number of core and valence electrons.
L02.1 Build & Discover
For the first 20 elements: maximum electrons on each energy level.
L02.1 Why different energy levels?