1.4 Bonding Flashcards
List the different types of chemical bonds.
ionic
covalent (incl. coordinate)
metallic
What is an ionic bond?
A bond formed by the electrical attraction between positive and negative ions (cations and anions)
What is a covalent bond?
A pair of electrons with opposed spin shared between two atoms with each atom giving one electron.
What is a coordinate bond?
A covalent bond in which both shared electrons come from one of the atoms.
Show the ionic bonding in sodium chloride.
Show the ionic bonding in magnesium fluoride
Show covalent bonding in chlorine
Show coordinate bonding in ammonia boron trifluoride
What does bonding result from?
Electrical attractions and repulsions between protons and electrons with attractions outweighing repulsions.
What does the degree of covalent and ionic character depend on?
The difference in electronegativity between the bonded atoms.
Define electronegativity.
A measure of the electron-attracting power if an atom in a covalent bond
What is the most electronegative element?
Fluorine
State the relationship between electronegativity and bonding.
The higher the electronegativity value, the better the element can attract bonding electrons
What is a polar bond?
A polar bond is one that has one end of the bond with a slightly positive charge and the other end with a slightly negative charge (i.e. dipole). The molecule is neutral overall.
What does it mean when a molecule is non polar?
If two atoms are the same, the atoms have equal electronegativities, so the electrons are equally shared and the bond is said to be non polar.
What is the electronegativity difference for a non-polar bond?
less than 0.4
What is the electronegativity difference for a polar covalent bond?
between 0.4 and 1.9
What is the electronegativity difference for an ionic bond?
2.0 or more.
Define intermolecular forces.
weak bonding holding molecules together
Define intramolecular forces.
strong bonding between the atoms in the molecules and governs its chemistry.
What are the 3 types of intermolecular forces?
- Dipole-dipole forces
- Induced dipole-induced dipole forces
- Hydrogen bonds
What molecules have dipole-dipole forces?
Polar molecules.
How does induced dipole forces occur?
Even molecules with no dipoles show intermolecular bonding.
Electrons are in constant motion so at any particular moment the distribution of the electron cloud around he nuclei will not be symmetrical. So at any particular moment, the molecule will have a temporary dipole.
The partial positive end can pull the electron cloud of a neighbouring molecule towards it giving a partially negative charge.
This induces a temporary dipole in the neighbouring molecule
What is Van der Waals forces?
Induced dipole-induced dipole forces and permanent dipole forces
