Chapter 6 Flashcards
Ionic bond
A chemical bond that results from the electrical attraction between anions and cations
What is a chemical bond?
A mutual electrical attraction between the nuclei and the valence electrons of different atoms that binds the atoms together.
Covalent Bonds
A chemical bond that results from sharing of electron pairs between two atoms
Nonpolar covalent Bond
Covalent Bond, where electrons are shared equally because their electronegativities are equal
Polar Covalent Bond
A covalent bond in which the bonded atoms have an unequal attraction b/c one atom had a greater electronegativity
When is it nonpolar covalent
<0.4
When is it polar covalent?
0.4-1.7
When is it ionic?
1.7<
What is a molecule
A neutral group of atoms that are held together by covalent bonds
Molecular compound
A chemical compound whose simplest units are molecules
What is a chemical formula?
Indicates the relative numbers of atoms of each kind w/subscripts and elemental symbols
Molecular Formula
Shows the types and numbers of atoms combined in a single molecule of a molecular compound (C6H126)
Diatomic Molecule
A molecule containing only two atoms
As two atoms come near one another, the nuclei of each atoms are attracted to the electrons of the other atoms…
This causes a decrease in the potential energy of the atoms
What is bond length?
Average distance between two bonded atoms
Bond energy
The energy required to break a chemical bond and form neutral, isolated atoms
What is an ionic compound?
Composed of positive and negative ions that are combine so that the number of positive and negative charges are equal
What is a formula unit?
The simplest collection of atoms from which an ionic compound’s formula can be established: NaCl
How do ionic bonds form?
An atom of an element w/ low electronegativity approaches another w/ high electronegativity; high transfers an electron from the atom w/ low. Anion and cation are formed
Polyatomic Ions
A covalently bonded group of atoms with a positive or a negative charge
Intramolecular
Inside the molecule
Intermolecular
Between 2 molecules
Which is stronger: intramolecular or intermolecular
Intramolecular
What properties reflect intermolecular forces?
Boiling points, melting points, viscosity, surface tension, and capillary action
Intermolecular force: weakest to strongest
Dispersion Forces (or London dispersion forces) -> Dipole-Dipole forces-> Hydrogen bonding (a special dipole-dipole force)->ion-Dipole forces
Dispersion Forces
Nonpolar particle can temporarily be polarized to allow dispersion force to form
What factors affect amount of dispersion force in a molecule?
- # of electrons in an atoms (inc. electrons, inc. dispersion force)
- size
- shape of molecules w/similar masses (more compact, dec. dispersion force)
If something is easy to polarize…
It has a lower boiling point
What is a dipole
Partial charge: s+ means partially positive; s- means partially negative
What are the strongest intermolecular forces between?
Polar molecules
What can bond polarity create?
A net polarity for whole molecule or individual bonds can cancel each other
Dipole-Dipole Interactions
Polar molecules have a more positive and a more negative end a dipole; opposite ends attract each other
In Dipole-Dipole Interactions, for molecules of almost equal mass…
the more polar the molecule, the higher its boiling point
When will the Dipole-Dipole Interactions or Dispersion Forces have a greater effect?
If two molecules are of comparable size and shape, dipole-dipole interactions will likely be the dominating force; if one molecule is much, larger, dispersion forces will likely determine its physical properties
What is hydrogen bonding?
The dipole-dipole interactions experienced when H is bonded to N, O, or F are unusually strong; an attraction between a hydrogen atom attached to a highly electronegative atoms and a nearby small electron negative atom in another molecule or chemical group
Ion-Dipole Interactions are found…
in solutions of ions; the strength of these forces is what makes it possible for ionic substances to dissolve in polar solvents
