Chemical Bonding Flashcards
What is an ionic bond?
Electrostatic forces of attraction between oppositely-charged ions
Ionic bonds are non-directional.
What is a covalent bond?
Electrostatic forces of attraction between a shared pair of electrons and positively charged nuclei.
What is a metallic bond?
Electrostatic forces of attraction between a lattice of positive ions and a sea of delocalised electrons.
Metallic bonds are non-directional.
What determines the strength of an ionic bond?
Charge density, which affects Lattice energy
What determines the strength of a metallic bond?
Charge density of cations
What determines the strength of a covalent bond?
4 factors
1) Effectiveness of atomic orbital overlap (how diffuse orbital is)
2) Number of bonds
3) Polarity
4) Presence of neighbouring lone pairs
What is a coordinate/dative bond? What are the requirements for one to form?
A bond where the shared pair of electrons is only provided by one of the bonding atoms.
The donating atom must have a lone pair of electrons, and the receiving atom must have a vacant, low-lying orbital to accept the electrons.
Determine and explain the shape of SF4
State its bond angle.
Since SF4 has four bond pairs of ELECTRONS and one lone pair OF ELECTRONS, it has
Trigonal bipyrimidal
See-saw, since it has one lone pair.
107 degrees.
Determine and explain the shape of PCl5
State its bond angle.
Trigonal bipyrimidal, since it has five regions of electron density and no lone pairs.
120 degrees on equatorial plane, 90 degrees from axial to equatorial.
Determine and explain the shape of SF6
State its bond angle.
Octahedral, since it has six regions of electron density and no lone pairs.
90 degrees.
Bond angle of tetrahedral
109.5 degrees
Draw IF2-
Linear with two lone pairs and a -1 charge.
Bond angle of trigonal planar
120 degrees
Determine and explain the shape of H2O
State its bond angle.
Tetrahedral, four regions of electron density.
Bent, two lone pairs.
105 degrees.
Draw SO3
Trigonal planar shape with every bond being S=O
Draw BH4
Tetrahedral, all B-H bonds.
VSEPR is used to predict the molecular geometry of a species where electron pairs around the central atom of a molecule are arranged as far apart as possible in space so as to minimise their repulsion.
just know that ig
Why does PCl5 exist and not NCl5?
P is an element in Period 3 with vacant, low-lying 3d orbitals that can accept more electrons and expand octet, while N in Period 2 has no such available orbitals and can only accommodate a maximum of 8 valence electrons.
Compare bond angles of tetrahedral, trigonal pyrimidal and bent
In tetrahedral the bond angle is the greatest at 109.5 degrees because it has 4 bond pairs and exhibits only bond pair-bond pair repulsion.
In trigonal pyrimidal it has 3 bond pairs and 1 lone pair. Lone pair-bond pair repulsion is greater than bond pair-bond pair repulsion, so the bond angle decreases to 107 degrees.
In bent, it has 2 bond pairs and 2 lone pairs. Lone pair-lone pair repulsion is greater than lone pair-bond pair and bond pair-bond pair repulsion, so the 2 lone pairs repel the bond pairs even more to 105 degrees.
A molecule is said to be polar when…
A molecule is polar when its overall net dipole is zero.
Why is there an unpaired electron in NO and NO2?
They are radicals
Name and rank the three types of intermolecular forces by strength.
Instantaneous dipole-induced dipole (weakest)
Permanent dipole-permanent dipole
Hydrogen bonding (actually a stronger form of pdpd)
How do idid interactions arise?
Idid interactions are caused by momentary movements of electron charge in atoms. They are present between all particles, including non-polar molecules.
Factors affecting strength of idid interactions
1) Electron cloud size (Polarisability)
2) Surface of area for molecular interaction
