Chemical Bonds Ionic and Covalent Bonding
Jan 21, 2016
Chemical Bonds
Ionic and Covalent Bonding
Chemical Bonds– Ionic: Metals + Nonmetals
– Covalent: Nonmetals + Nonmetals• Sharing of electrons• Mostly gases, some liquids and
amorphous solids
– Metallic: • Metal atoms bonded to several other metal atoms
Ionic Compounds *
Properties of Ionic Compounds
• At room temperature, most are cystalline solids
• Very attractive forces
Ionic Compounds (Salts):• Composed of a Metal ion (cation, M+) combined with an Non-
Metal ion (anion, N-); atoms exchange transfer electrons.• Are Crystalline Solids. • Have high melting points• Smallest component particle is called a formula unit, not a
molecule.
Cations
Anions
Types of Ions
• Monoatomic ion has only one atom examples are chloride, Cl-, fluoride, F-, sodium Na+
• Polyatomic ion has more than one, ex. sulfate (SO4
2-), nitrate (NO3-)
What is the octet rule???
• Octet Rule says that atoms tend to gain, lose or share electrons so as to have eight electrons in their outer electron shell
• Composed of a Non-Metal combined with another Non-Metal.
• Are mostly gases, liquids, and sometimes amorphous solids.
• Have low melting points• Bonded atoms share electrons.
Covalent (Molecular) Compounds:
H2O(s)
*
H2O(l)
H2O(g)
Covalent Bonding• Equal & Unequal sharing of electrons:
Electronegativity, Polarity and Miscibility
• Representation of covalent bonding using
Lewis Structures
• Energetics
Polar vs. Non-Polar
• Polar:– A type of covalent bond
in which the electrons are NOT shared equally.
– When atoms of different electronegativities form a bond, the electrons tend to be more controlled by the atom with the higher electronegativity.
Non-Polar
• A non-polar bond is one in which the electrons are shared equally.
• Covalent bond that has no positive or negative 'ends'.
What are single, double, and triple bonds??
• ONLY refers to covalent bonds• A single bond is a bond in which two atoms
share a pair of electrons.• A double bond is a bond that involves two
shared pairs of electrons.• A triple bond is a bond that involves three
shared pairs of electrons
Bonding Theories
(1) Valence Shell Electron Pair Repulsion (VSEPR) Theory: considers only the valence electrons and their geometry when they repel each other when they form bonds.
“The best arrangement of a given number of electron domains is the one that minimizes the repulsions among
them.”
VSEPR Theory• Based on Lewis structures we can know the
shape or “geometry” of molecules
• VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion
• Electrons around the central nucleus repel each other. Thus, resulting structures have atoms maximally spread out