Physical - 1.3 Bonding Flashcards
Define coordinate bond
A coordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom.
Define covalent bond
A shared pair of electrons between two non-metals.
Define dipole
Difference in charge between the two atoms of a covalent bond caused by shift in electron density in the bond due to the electronegativity difference between elements participating in bonding
Define electron pair repulsion
Repulsion that exists between electron repairs due to negatively charged electrons.
Repulsion means electron pairs position themselves as far apart from each other as possible around the central metal at
Define electronegativity
The power of an atom to attract the electron density in a covalent bond towards itself
Define electrostatic forces
The strong forces of attraction between oppositely charged ions
Define hydrogen bonding
An interaction between a hydrogen atom and an electronegative atom, commonly nitrogen, fluorine or oxygen. The slightly positive hydrogen is attracted to the lone pair on the electronegative atom. Hydrogen bonds are stronger than van der waals and dipole dipole forces but weaker than ionic and covalent bonds.
Define intermolecular forces
The forces which exist between molecules. The strength of the intermolecular forces impact physical properties like boiling and melting point.
Define ion
An atom molecule with an electric charge due to the loss or gain of electrons
Define ionic bond
A metal atom loses electrons to form a positively charged ion and a non-metal atom gains these electrons to form a negatively charged ion. An ionic bond is formed between charged ions.
Define ionic compound
Chemical compound formed of ions, held together strong acid forces.
Define lattice structure
Repeating regular arrangement of atom/ion/molecules. This arrangement occurs in crystal structures.
Define macromolecular crystal structure
Giant covalent structures. Macro molecules have very high melting points because many strong covalent bonds have to be broken. Examples include diamond and graphite.
Define metallic bond
The bond present in metals between the positive metal ions and negative recharge electrons
Define permanent dipole dipole forces
When molecules with polar covalent bonds interact with dipoles in other molecules dipole dipole intermolecular forces are produced between the molecules. These intermolecular forces are generally stronger than van der waals forces but weaker than hydrogen bonding.
Define polar bond
Covalent bond between two atoms in which the electrons in the bond are evenly distributed. This causes a slight difference, inducing a dipole in the molecule.
Define simple molecular crystal structure
Structures in which the atoms are joined by strong covalent bonds. Weak intermolecular forces mean simple molecules have low melting and boiling points.
Define van der waals forces
Also known as induced dipole dipole, dispersion and London forces, van der Waals forces exist between all molecules. They rise due to fluctuations of electron density within a nonpolar molecule. These fluctuations may temporarily cause an uneven electron distribution, producing an instantaneous dipole. This dipole can induce the dipole in another molecule, and so on.
What is the VSEPR theory?
Valence shell electron repulsion theory is used to deduce the geometry of molecules. Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion. Loan pair-loan pair repulsion is greater than lone pair-bond pair repulsion, which is greater than bond pair-bond pair repulsion.
What is an iconic bond between?
Metals and non-metals with a large difference in electronegativity
What is an example of a molecule with ionic bonding?
NaCl
Sodium chloride
What are the properties of giant ionic lattices?
- High mp due to a strong attraction between oppositely charged ions
- Electrical conductance when molten/in solution as ions are free to move and therefore carry charge
What are the two types of covalent structure?
Macromolecular
Molecular
What is a covalent bond between?
Non-metals
What is a covalent bond?
A shared pair of electrons
What is an example of a macro molecular structure?
Diamonds/silicon
Graphite
What is an example of a molecular covalent structure?
Iodine
What are the properties of macro molecular structures?
- High mp due to lots of strong covalent bonds (diamond)
- Dry lubricant due to weak VDW between layers (graphite)
- Conduct electricity (graphite)
What are the properties of molecular covalent structures?
Low bp due to weak VDW forces between molecules.
What is a metallic bond between?
Only metals
What is a metallic bond?
Attraction between positive ions and negative delocalised electrons.
An example of a metallic bond is…
Magnesium
What are the properties of a metallic substance?
- High mp due to the strong attraction between positive ions and negative delocalised elections.
- Electrical conductance due to delocalised electrons that can carry charge.
- Malleable/ductile
2 pairs
2 bonding
0 lone
Linear shape
180
3 pairs
3 bonding
0 lone
Trigonal planar
120
4 pairs
4 bonding
0 lone
Tetrahedral
109.5
5 pairs
5 bonding
0 lone
Trigonal bipyramidal
90 and 120
6 pairs
6 bonding
0 lone
Octahedral
90
4 pairs
3 bonding
1 lone
Pyramidal
107
4 pairs
2 bonded
2 lone
Bent
104.5
5 pairs
3 bonded
2 lone
T-Shaped
86
5 pairs
2 bonded
3 lone
Linear
180
6 pairs
4 bonded
2 lone
Square Planar
90
