Structure 2 - Models of bonding and structure Flashcards
Why is a metallic bond non-directional?
Electrons shared with every cation
Lattice
3D repeating structure
Properties of metals
Good thermal and electrical conductors
melleable
strength
Can two metals bond together?
Yes but most likely through an alloy (multiple metals). Brass contains copper and zinc
Ionic bond
A strong electrostatic attraction between positive and negative ions
Binary ionic compound
A binary ionic compound is composed of ions of two different elements like sodium iodide and sodium chloride. A non binary ionic bond is NaNO₃.
Monatomic ion
A monatomic ion is a ion that consists of only one atom “Monobrow”
Polyatomic ion
A polyatomic ion is an ion that consists of two or more atoms such as sulphate.
Ionic lattice
An ionic lattice is a regular repeating structure consisting of alternating cations and anions. Also 3D.
Bonding of ionic compound
Electrostatic attraction between cations and anions. Ionic bond
Characteristics of ionic bonding
Not volatile
Soluble in water
Brittle
Covalent bond
Bonds form to form a stable electron configuration and release energy. Electrons are shared
Octet rule
Tendency of atoms to prefer to have 8 electrons in the valence shell
What is the duplet rule and what elements does it apply to?
Same as octet rule except it’s a tendency to have 2 electrons in valence shell. This applies to hydrogen
Difference between lone pair and bonding pair of electrons?
Lone pair - not bonded to another element
Bonded pair - bonded to another element
Sigma bond
Caused by direct overlap of two orbitals and is stronger than pi bonds. Every covalent bond has a sigma bond.
Pi bond
Caused by sideways overlap of two orbitals and is much weaker than sigma bonds.
Coordination bond
Both electrons shared from same atom. Often shown by an arrow pointing from the atom which donates the lone pair to the atom which receives it.
Resonance
Molecule or polyatomic ion for which two possible Lewis formula’s can be drawn.
Resonance hybrid
More stable than Lewis structures and is when more than two possible Lewis structures.
Electronegativity
Ability of an atom to attract a bonding pair of electrons in a covalent bond.
Dipole moment
Measure of net polarity which is the magnitude of charge at either end of the molecular dipole times the distance between charges.
London forces
- Exist in all molecules
- May also be known as dispersion forces or instantaneous induced dipole-dipole forces
More info in revision book
What affects the magnitude of London forces?
- Number of electrons
- Size of electron cloud
- Shapes of molecules
Dipole-Dipole forces
Electrostatic attraction between positive permanent dipole on one molecule to a negative dipole on an adjacent molecule.
Created by a difference in electronegativity
Hydrogen bonding
An attractive interaction between hydrogen and another atom which has a higher electronegativity than hydrogen such as fluorine, nitrogen and oxygen.
Two types of electrostatic forces
Intramolecular - inside molecules
Intermolecular - between molecules
Strongest to weakest intermolecular bonds
Hydrogen bonding - strongest
Dipole-Dipole
London forces - weakest
Electron geometry
Shape of all electron domains
Molecular geometry
Shape formed by just the atoms in a molecule
What structure will form with just 2 electron domains?
0 lone pairs = Linear - bond angle 180 degrees
What structure will form with just 3 electron domains?
0 lone pairs = Trigonal planar - bond angle 120 degrees
1 lone pair = Bent - bond angle - bond angle 117 degrees
What structure will form with 4 electron domains?
0 lone pairs = Tetrahedral - bond angle 109.5 degrees
1 lone pair = Trigonal pyrimidal - bond angle 107 degrees
2 lone pairs = Bent - bond angle 104.5 degrees
What structure will form with 5 electron domains?
0 lone pairs = Trigonal bipyrimidal - bond angle 90 and 120 degrees
1 lone pair = sawhorse - bond angle 120 degrees
What structure will form with 6 electron domains?
0 lone pairs = Octahedral - bond angle 90 degrees
Ligand
Molecule that can donate a pair of electrons such as H2O. They attach to a transition metal.
Formal charge formula
Formal charge (No. of valence electrons) - ((No. of non-bonded electrons) + 1/2 (No. of bonded electrons))
What does the formal charge formula determine?
Used to determine the correct Lewis structure
What is hybridisation?
the process of combining two atomic orbitals to create a new type of hybridised orbitals.
sp3 - 4 hybrid orbitals - tetrahedral, 109.5 degrees
sp2 - 3 hybrid orbitals - trigonal planar, 120 degrees
sp - 2 hybrid orbitals - linear, 180 degrees
amount of hybrid orbitals = amount of electron domains
Limitations of the van arkel-ketelaar triangle
Doesn’t work for more than two elements
Doesn’t take into account differences in structure meaning for example it suggests all allotropes of carbon have the same melting point
