Bonding And Structure Flashcards
Giant ionic lattices have high or low melting and boiling point? Explain your answer.
They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds.
In what type of solvents do ionic lattices dissolve?
Polar solvents
Why are ionic compounds soluble in water?
Water has a polar bond. Hydrogen atoms have a + charge and oxygen atoms have a - charge. These charges are able to attract charged ions.
What is average bond enthalpy?
Measure of average energy needed to break the bond.
What is a dative covalent bond?
A bond where both of the shared electrons are supplied by one atom.
How are oxonium ions formed?
Formed when acid is added to water, H30+
What does expansion of the octet mean?
When a bonded atom has more that 8 electrons in the outer shell
What are the types of covalent structure?
- simple molecular lattice
- giant covalent lattice
Describe the bonding in simple molecular structures.
Atoms within the same molecule are held together by strong covalent bonds and different molecules are held by weak intermolecular forces.
Simple molecular structures dissolve in what type of solvent?
Non polar solvents
Give examples of giant covalent structures
- diamond
- graphite
- silicon dioxide
List some properties of giant covalent structures? (3)
- high melting point and boiling point
- non conductors of electricity except graphite
- insoluble in polar and non polar solvents
Draw and describe the structure of a diamond.
3D tetrahedral structure of C atoms, with each C atom bonded to four others.
What does the shape of a molecule depend on?
NO. Electron pairs in outer shell
NO, bonded pairs and lone pairs
What is the shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs?
Trigonal bipyramid
90 degrees and 120 degrees
What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs?
Octahedral
90
By how many degrees does each lone pair reduce the bond angle?
2.5 degrees
Define electronegativity
The ability of an atom to attract the pair of electrons in a covalent bond
What is the most electronegative element?
Fluorine
Why is H2O polar, whereas CO2 is non polar?
CO2 is a symmetrical molecule, so there is no overall dipole
What is meant by intermolecular force?
Attractive force between neighbouring molecules
Describe london forces.
- london forces are caused by random movements of electrons
- this leads to instantaneous dipoles
- instantaneous dipole induces a dipole in nearby molecules
- induced dipoles attract one another
Does boiling point increase or decrease down the noble gas group? Why?
Boiling point increases because the no. electrons increases and therefore the strength of london forces also increases
Why is ice less dense that liquid water?
In ice the water molecules are arranged in an orderly pattern. It has an open lattice with hydrogen bonds
In water, the lattice is collapsed and the molecules are closer together
Why does water have a high melting/boiling point that expected?
Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces.
