Electronic Configurations Flashcards

All 5 cards in this deck

How many electrons fill the first, second and third shells for the first 20 elements?

First shell 2, second shell 8, third shell 8 (then the fourth shell starts).

What are the steps to write the electronic configuration of one of the first 20 elements?
e.g. sodium, atomic number 11

1. Number of electrons = atomic number: 11
2. Fill the first shell with 2: 2
3. Fill the next shells (8, then 8) until all electrons are used: 2.8.1

What are the steps to draw the electronic configuration of an atom as a shell diagram?
e.g. oxygen, atomic number 8

1. Draw the nucleus and label it with the symbol: O
2. Add a circle (shell) and put 2 electrons on it: 2
3. Add further shells, up to 8 electrons each, until all are drawn: 6 on the second shell (2.6)

True or false? An atom with the electronic configuration 2.8.3 is in group 3 and period 3.

True. 3 outer electrons gives group 3; 3 occupied shells gives period 3.

True or false? Group 0 elements have no electrons in their outer shell.

False. They have a full outer shell — 8 electrons (helium has 2).