Unit 3: Lewis Theory Flashcards
(32 cards)
What does Lewis theory state about why atoms bond?
Atoms bond to achieve noble gas configurations (octets or duets).
What are the two main types of chemical bonds in Lewis theory?
Ionic and covalent bonds.
What is an ionic bond?
A bond formed by the transfer of electrons from one atom to another.
What is a covalent bond?
A bond formed by the sharing of electrons between atoms.
What is a Lewis symbol?
A symbol that shows valence electrons as dots around an element’s chemical symbol.
How many electrons does hydrogen need for a full outer shell?
2 (duet rule).
What is the octet rule?
Atoms tend to bond in a way that gives them 8 electrons in their valence shell.
When are Lewis structures used?
To represent how atoms share or transfer electrons in molecules.
What types of elements are involved in covalent bonding?
Nonmetals.
What types of elements are involved in ionic bonding?
Metals and nonmetals.
What does a line between atoms in a Lewis structure represent?
A shared pair of electrons (covalent bond).
What does electronegativity measure?
An atom’s ability to attract shared electrons in a bond.
What kind of bond forms with equal sharing of electrons?
Non-polar covalent bond.
What kind of bond forms with unequal sharing of electrons?
Polar covalent bond.
How are dipole moments shown in polar molecules?
With an arrow pointing toward the more electronegative atom.
What is a resonance structure?
Alternative Lewis structures for the same molecule showing delocalized electrons.
Why do some atoms have incomplete octets?
They have fewer than 8 valence electrons (e.g. B, Be).
Why do some atoms have expanded octets?
They are in period 3 or beyond and can use d orbitals.
What is formal charge?
The charge assigned to an atom in a Lewis structure based on valence electrons.
How is formal charge calculated?
Valence electrons - (lone pair electrons + bonds).
What is the best Lewis structure for a molecule?
The one with the lowest formal charges and proper octets.
What element is always terminal in Lewis structures?
Hydrogen.
Which atom is usually central in a Lewis structure?
The least electronegative atom.
What do multiple bonds count as in Lewis structures?
One electron group.
