Valence Electrons in Lewis Structures: Roman Numerals & Electron Configurations, Study notes of Chemistry

Download Valence Electrons in Lewis Structures: Roman Numerals & Electron Configurations and more Study notes Chemistry in PDF only on Docsity!

Lewis Structures

• Valence electrons – the electron(s) in the atom’s highest

energy level.

• Remember your electron configurations! IN YOUR FOLDER LOOK AT YOUR ELECTRON CONFIGURATION PERIODIC TABLE.
• What is the electron configuration for Lithium?

1s^2 2s^1

• The highest energy level for Lithium is 2 and there is a single electron in this energy level. Therefore, Lithium has ONE valence electron.
• How many valence electrons does Beryllium have?

1s^2 2s^2 , So Beryllium has TWO valence electrons.

• Boron?
• 1s^2 2s^2 2p^1 , So Boron has THREE valence electrons.

HINT: The highest energy level’s (s + p) = # valence electrons

• Everybody have a periodic table?
• Across the top you will see Roman numerals followed by either an A or B. Look only at the groups with Roman numerals followed by an A. This trick does not work with transition elements!!!
• The Roman numeral tells the number of valence electrons for every element in that group/column.

I A = 1 valence electron II A = 2 valence electrons III A = 3 valence electrons IV A = 4 valence electrons V A = 5 valence electrons VI A = 6 valence electrons VII A = 7 valence electrons VIII A = 8 valence electrons.

Exception to the Roman

numeral short cut!!!!

Does Helium have 8 electrons?

How many protons? As a neutral element it has

same number of electrons!!

Also Helium is 1s^2

ONLY TWO VALENCE ELECTRONS – ONLY

TWO ELECTRONS PERIOD!!!!

• Lewis structures – dots representing valence

electrons

• The dots are placed one at a time on the four

sides of the symbol and then paired up until all

are used.

• Example: Boron – 1s^2 2s^2 2p^1 or III A – either

way you want to think about it, Boron has

THREE valence electrons.

Lewis Structure

B