5. Chemical Bonding Flashcards
Compund
A substance made of two or more elements chemicals combined
Octet rule
When bonding occurs, atoms tend to reach an electron arrangement with 8 electrons in the outermost energy level.
What are the exceptions to the octet rule?
Transition metals
Hydrogen, Lithium & Beryllium (2)
Ion
A charged atom or group of atoms.
Cations
Positive ions
Anions
Negative ions
Ionic bond , eg
The force of attraction between oppositely charged ions in a compound. Ionic bonds are always formed by the complete transfer of electrons from one atom to another.
Eg NaCl
What is the name of the three dimensional structure in which ions are encased?
Crystal lattice
3 characteristics of transition metals
- variable valency
- coloured compounds
- catalysts
VCC
What elements included in the d block are not actually transition metals?
Scandium and Zinc
Transition metal
One that forms at least one ion with a partially filled d sublevel.
Molecule
A group of atoms joined together. It is the smallest particle of an element or compound that can exist independently.
Valency
Valency of an element is defined as the no. of atoms of hydrogen or any other monovalent element with which each atom of the element combines.
Sigma bond
A sigma bond is formed by the head on overlap of two orbitals.
(Single bonds) eg H2
Pi bond
Pi bonds are formed by the sideways overlap of p orbitals.
Eg O2
What type of bonds make up a single bond?
1 sigma bond
What type of bonds make up a double bond?
1 sigma
1 pi bond
What type of bonds make up triple bonds?
1 sigma
2 pi
Which are stronger, sigma or pi bonds?
Sigma ; as there is more overlapping of orbitals in sigma bonds
Therefore O=O is not twice as strong as O-O.
VSEPR
Valence Shell Electron Pair Repulsion
Electron pairs repel each other and arrange themselves in space so they can be as far apart as possible
Angle of Triangular Planar
120
Angle of linear
180
Angle of pyramidal
107
Angle of V shaped
104.5
Angle of Tetrahedral
109.5
Electronegativity
The relative attraction that an atom in a molecule has for the shared pair(s) of electrons in a covalent bond.
Polar covalent bond
A bond in which there is unequal sharing of the pair(s) of electrons. This causes one end of the bond to be slightly negative and the other end slightly positive.
Pure covalent
Equal sharing
Exception to polar covalent bonds
Symmetrical molecules eg CO2 where the center of the negative charges coincide with that of the positive charges .
Demonstrate polarity of water molecule
A charged plastic rod will always attract the water stream, whether negative or positive charged. Bc water molecules spin so that the neg/pod charge are attracted to rod.
Predicting type of bonding based one electronegativity values
0- non polar (pure covalent)
0-0.4 negligible polar covalent
0.4-1.7 polar covalent
1.7+ ionic
Intramolecular bonding
Bonding that takes place within the molecule ie it holds the atoms together. Eg Covalent, polar covalent
Intermolecular forces
The forces of attraction that exist between molecules. Eg Van der Waals, dipole-dipole, hydrogen bonds.
Van der Waals forces
Weak attractive forces between molecules resulting from the formation of temporary dipoles. They are the only forces of attraction between non-polar molecules
Eg. H2
Dipole-dipole forces
The forces of attraction between the negative pole of one polar molecule and the positive pole of another polar molecule. Eg HCl
Hydrogen Bonds
Particular types of dipole-dipole attractions between molecules in which hydrogen atoms are bonded with nitrogen, oxygen or fluorine.
NOF
