How to Draw Lewis Structures

Lewis Structures Find your element on the periodic table. Determine the number of valence electrons. This is how many electrons you will draw.

Lewis Structures Find out which group (column) your element is in. This will tell you the number of valence electrons your element has. You will only draw the valence electrons.

Groups - Review Group 8 = 8 electrons Group 1 = 1 electron Except for He, it has 2 electrons Group 2 = 2 electrons Each column is called a “group” 3, 4, 5, 6, 7 Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. The electrons in the outer shell are called “valence electrons”

C Lewis Structures Write the element symbol. Carbon is in the 4th group, so it has 4 valence electrons. Starting on one side, rotate around giving an electron on each side If you have more than 4 electrons, then double up C

C Lewis Structures Check your work. Using your periodic table, check that Carbon is in the 4th group. You should have 4 total electrons, or dots, drawn in for Carbon. C

C Lewis Structures On your whiteboard, try these elements: Rb P Ca Ar Al B As F C

Forming Ions What is an ion? An electrically charged particle formed when an atom gains or looses an electron Loosing electrons form positively charged ions called cations Gaining electrons form negatively charged ions called anions

Forming ions

Forming Ions The octet rule Atoms are most stable when they have full valence shells Gain or loose electrons to have 8 or 0 valence electrons Will gain or loose …. Which ever involves the fewest electrons moving

Forming ions Remember gaining electrons makes you negative! Loosing electrons makes you positive!

Cl Mg Forming ions For example, Chlorine Magnesium Group 7A 7 valence electrons Wants to gain 1 more Ends with a -1 charge Magnesium Group 2A 2 valence electrons Wants to loose 2 Ends with a +2 charge Cl Mg

Forming ions On your whiteboard, try these elements: Rb P Ca Ar Cl Al As F