Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Let's start by counting the total number of valence electrons in the molecule we need to draw. Can anyone tell me how to determine the number of valence electrons for an atom?
Isn't it based on the group number of the elements in the periodic table?
Exactly! Elements in Group 1 have 1 valence electron, Group 2 have 2, and so forth. Now, if we take water (H2O) as an example, how many valence electrons does it have?
Oxygen has 6, and each hydrogen has 1, so 6 plus 2 equals 8!
Right! We start with 8 total valence electrons. Excellent job!
Next, we need to determine the central atom of H2O. What do you think?
It should be oxygen since it can form more bonds than hydrogen.
Correct! Oxygen is less electronegative and can form two bonds. Remember, hydrogen can only bond once and will never be the central atom in a structure. Now, what do we do next?
We draw the single bonds from the central atom to the surrounding atoms!
Exactly! Each bond uses 2 valence electrons.
We have drawn our bonds. Now, how do we ensure that the outer atoms have complete octets?
We add lone pairs to them until they have 8 electrons. But hydrogen only needs 2.
Great point! So now, we’ll put 4 electrons on oxygen and 2 for each hydrogen. What if we had leftover electrons?
Those go on the central atom!
Exactly right! In H2O, oxygen ends up with 2 lone pairs, fulfilling its octet rule.
Sometimes the central atom doesn’t have a complete octet after placing all available electrons. What do we do then?
We can make double or triple bonds by sharing electrons!
Correct! If we had a molecule like carbon dioxide (CO2), which has two oxygen atoms bonded to a central carbon, how would we adjust that structure?
We would convert lone pairs of oxygen into double bonds to give carbon its octet.
Well done! Carbon dioxide indeed has two double bonds, ensuring all atoms achieve a stable electron configuration.
Essential step to begin drawing Lewis structures by tallying available valence electrons from each atom.
The central atom is typically the least electronegative atom that forms multiple bonds.
Most atoms aim for a stable configuration of eight electrons in their valence shell.
Atoms can share more than one pair of electrons to satisfy the octet rule.
To create a Lewis, first count up the shells, then bond up the atoms, and octets you’ll tell.
Imagine a floating family of fish looking for their home (the central atom) in a vast ocean (the valence electrons) where they share their treasures (electrons) to become stable and cozy.
C-C-C-O-L-P: Count, Central atom, Connect, Complete octet, Lone pairs, Possible bonds.
When drawing Lewis, remember CCL-C: Count, Choose, Link, Complete, and Loop back for multiple bonds.
Term
What is the central atom?
Click to flip
Term
What is the octet rule?
Click to flip
A diagram representing the arrangement of valence electrons in a molecule, illustrating bonds and lone pairs.
Electrons located in the outermost shell of an atom that are involved in bonding.
The atom in a Lewis structure typically bonding with multiple atoms, usually the least electronegative.
A principle stating that atoms tend to form bonds in such a way that they have eight electrons in their valence shell.
Bonds formed by sharing more than one pair of electrons between atoms, such as double or triple bonds.
This section outlines the essential steps to draw Lewis structures, which represent the arrangement of valence electrons in a molecule.
The steps for drawing Lewis structures include counting valence electrons, identifying the central atom, connecting atoms with single bonds, completing octets, placing lone pairs, and forming multiple bonds if needed, which collectively provide insight into molecular bonding.
Lewis structures, also known as electron dot structures, are schematic diagrams that depict the distribution of valence electrons within atoms in a molecule or polyatomic ion. Drawing a Lewis structure is critical for comprehending molecular bonding and geometry, which is foundational for more advanced topics in chemistry. The step-by-step methodology involves the following:
This structured approach not only helps in accurately drawing Lewis structures but also lays the groundwork for understanding molecular geometries and reactivity.