1A3 Bonding and Structure Flashcards
What is lattice?
Regular 3-dimensional arrangement
What is factor affecting ionic bond strenght?
The strenght increase as:
The charge on the ion gets larger
Radius of the ion gets smaller
What are the properties of ionic compounds and reason?
Solid at room temperature - particles held together in a fixed lattice
High melting point - force holding the particles together are strong ionic attraction
Usually soluble in water - H2O particles are polar so form bond with ionic
Insoluble in organic solvents - very weakly polar so cannot form bond
Does not conduct electricity when solid - particles are charged but cannot from their fixed position to carry electricity
Conducts electricity in molten or solution state - particles can move freely so cam move and carry electricity
What is definition of covalent bonding?
Shared pair of electrons is the covalent bond
Is covalent bond held atoms called molecules, particles or dots?
Molecules
What is co-ordinate bonding?
Same as covalent bond but both electron in the shared pair come from one of the atoms in a bond
If a coordinate bond forms it is identical to normal covalent bonding
What is properties of simple molecular substances and why?
Often gaseous or volatile liquid at room temperature and low melting point - not strongly attracted to each other as weak intermolecular forces
Does not conduct electricity at all - no charged particles to move and carry electricity in electric field
Insoluble in water but soluble in organic solvent - forces between H2O too strong while organic solvents has same strenght
What is properties of metallic bond and why?
Solid at room temperature and high melting point - held in fixed position in lattice so strong
Conduct electricity well - delocalised e- can move freely in an electrical field
Strong, malleable and ductile - layers of metal atoms can slide over each other under pressure but remain attached
Define electronegativity?
Power of an atom to attract the electron in covalent bond
How does increase electronegativity in periodic table?
Across a period
Up a group
Why does electronegativity increse?
Increase in nuclear charge and decrease in radius and shielding
What is non-polar covalent bond?
Between 2 atoms of same type, en is same so electron density is shared equally and symetrical
What is polar covalent bond?
When 2 atoms with different en foms bond, the atom with more en will have greater attraction for shared pair e-
So density is pulled to it and asymmetric distribution of e-
So polar bond
So it is thought to have ionic character
The bigger difference in en, the more polar
When this gets big enough it becomes ionic
What is types of different ionic and covalent bodns?
Perfect ionic bond - spherical
Ionic bond with colavent chatacter - small cation(+), big anion(-) polarised so not spherical
Polar covalent bond - difference in en, permanent dipole but e- pair shared
Perfect covalent bond - no difference in en, shared pair of e- and electron density evenly distributed
State intermolecular forces in order of increasing strenght?
London forces
Permanent dipole-dipole forces
Hydrogen bonds
What is london force?
Attraction of one atoms nucleus to another atoms e-, causing an atom in one molecule can stick to an atom
Its strenght depends on:
-size of molecule with increasing Mr
-surface area i.e. as molecule gets less spherical
What is permanent dipole-dipole?
Attract opposite charges on other molecules
What is hydrogen bonds?
Special case of dipole-dipole forces
There has to be covalent bonds between and hydogen and eithr of N,O or F
State 4 types of crystal?
Ionic
Metallic
Molecular
Macromolecular
What is ionic crystal?
Consist of giant lattice of + and - ions
+ ions is surrounded by - ions vice versa
Electrostatic force of attraction happens in between
Number of ions surrounding one opposite ion depends on specific compounds
What is metallic crystal?
Lattice of cations which are held in place by a cloud of e-
e- are free to move throughout the lattice in a delocalised orbital
+ ions are very closely packed layers
What is molecular crystal?
Covalent molecules held by london forces, permanent dipole dipole and hydrogen bonds
Low metling and boiling point
Process which solid goes directly to vapour is called sublimation
What is macromolecular crystal?
Giant molecular structures in which all the atoms are joined by covalent bonds
Allotropes of carbon called graphite and diamond is examples
What is diamond arrangement called?
Tetrahedral
What is graphite?
C is covalently bonded to 3 other C in hexagonal arrangement
Layers of hexagon is arranged by london forces
As only uses 3 e- to form bonds the remaining e- delocalised between the layers
State all shapes name, angles involved and number of sets of e- of molecules?
Linear, 180, 2bp
Trigonal planar, 120, 3bp
Tetrahedral, 109.5, 4bp
Trigonal bipyramidal, 90 and 120, 5bp
Octahedral, 90, 6bp
Pyramidal, 107, 3bp and 1lp
V-shaped, 104.5, 2bp and 2lp
T-shaped, 87.5, 3bp and 2lp
Square planar, 90, 4bp and 2lp
