MCAT General Chemistry - Bonding and Chemical Interactions

Chemical bonds

strong attractive forces that hold molecules together

Octet Rule

Atom tends to bond with other atoms so that it has eight electrons in its outermost shell

Incomplete Octet

These elements are stable with fewer eight electrons in valence shell

Expanded Octet

Any element in period three and greater can hold more than eight electrons,

Odd number electron

Any molecule with an odd number of valence electron cannot distribute those electron equally to give eight to each atom

Ionic Bond

One or more electron from an atom with low ionization energy are transferred to an atom with high electron affinity

Covalent Bonding

electron pair i shared between two atoms that have relatively simular values of electronegativity

Coordinate Covalent

If both the shared electron are contributed by only one of the two

Ionic bond

form between atoms that have significantly different EN

bond order

The number of shared eelctrons between two atoms

Bond length

average distance between two nuclei of atoms in a bond

Relationship between bond order and length

As bond order increases, bond length decreases

Characteristic of ionic bond

high melting and boiling point, dissolve readily in water/polar solvent, good conductor of electricity,

Bond energy

energy required to break a bond by separating its components into their isolated, gaseous atomic states

Relationship between bond order and energy

greater bond order, greater bond energy

Polar Covalent Bonds

Atoms that differ moderately in their electronegativity will share electrons unevenly

Dipole moment

Vector quantity given by equation

Debye Units

measure dipole moments

Bonding electrons

electrons involved in covalent bond are in the valence shell

Nonbonding electrons

electron in valence shell not involved in covalent bonds

Lewis Dot Diagram

Chemical symbol of an element surrounded by dots, each representing one of the S or P valence electron of the atom

Formal Charge

Difference between the numnber of electron assigned to an atom in a Lewis Structure and number of electorn normally found in that atom valence shell

Resonance Structures

Two or more Lewis structures that demonstrate same arrangement of atoms but differ specific displacement of electron

Valence Shell Electron Pair Repulsion

A system that reflects the geometric arrangement of a molecule based on lewis dot structure, the 3D structure is determined by repulsion between bonding and nonbonding electron pairs in the valence shell of atoms

Electronic geometry

Spatial arrangement of all pairs of electron aroudn the central atom, including bonding and lone pairs

Molecular geometry

Spatial arrangement of only bonding pairs of electrons

Coordination Number

Number of atoms that surround and are bonded to central atom

Bonding Orbital

signs of two atomic orbtials are the same

Antibonding orbital

Signs of two atomic orbitals are different

Sigma Bond

Orbitals ovrlap head to head

Pi Bond

Orbitals overlap such way two parallel electron cloud densities

Intramolecular Forces

The attractive forces between atoms within a single molecule

Dispersion Forces

IM forces arising from interactions between temporary dipoles in molecules

Dipole Dipole Interactions

The attractive force between two dipole, magnitude dependent on both dipole moments and distance between two species

Hydrogen Bonds

Specific, unusually strong form of dipole dipole interaction that may be intra or intermolecular