Drawing Lewis Structures Worksheet (Page 2 of 2) in pdf

Drawing Lewis Structures Worksheet Page 2

LEWIS STRUCTURES

Steps for Drawing:

Count up the total number of valence electrons in the structure.

NOTE: For A-Group elements, the number of valence electrons is equal to the Group

number.

Decide on a skeletal structure (what’ s bonded to what).

The central atom is generally written first in the chemical formula.

Hydrogen is never the central atom but is usually written first in acids.

Place two electrons in each bond.

Surround each of the non-central atoms with an octet of electrons.

NOTE: Hydrogen is an exception and is only surrounded by two electrons.

Determine how many electrons are left. Place any remaining electrons on the central atom

in pairs.

If the central atom does not have an octet of electrons, form double or triple bonds to give

it an octet of electrons.

NOTE: H, B, Be, F and metals do not generally form multiple bonds.

If the central atom in Step #6 does not form multiple bonds, leave it short of electrons.

NOTE: H is generally surrounded by 2 electrons; Be, by 4 electrons and B, by 6

electrons.

Valence:

Number of bonds that an atom of an element likes to form in covalent compounds.

This is also equal to the number of e- needed to complete the octet. Use valences

to easily and quickly draw Lewis structures for organic substances.

Common Valences:

Non-metals in Groups:

IVA

VIA

VIIA

Example:

Carbon in Group IVA has a valence of 4 and consequently likes to form 4

bonds. These four bonds can consist of:

four single bonds

one double and two single bonds

one triple and one single bond

two double bonds

Drawing Lewis Structures Worksheet Page 2