Chapter 6 - Flashcards
expanding the octet?
- the bonding atoms will have more than 8 electrons in the outer shells
- this can occur in Group 15-17, period 3 downwards
Group 15 Non metals can form?
3 or 5 covalent bonds
Group 16 non metals can form?
2,4, or 6 covalent bonds
group 17 non metals can form?
1,3,5,7 covalent bonds
what is electronegativity?
the ability of an atom to attract the bonding electrons in a covalent bond
how is electronegativity measured?
on the Pauling scale
electronegativity trends ?
increases across a period, up a group
* IN ALL DIRECTIONS TOWARDS FLUORINE
why does electronegativity increase across a period ?
as the charge on the nucleus increases across a period, the number of protons in nucleus increases, therefore is increased attraction for the outer electrons , the bonded pair of electrons are attracted more strongly
why does electronegativity increase up a group?
- bc down the group, the boning pair of electrons is held increasingly further away from the nucleus bc. the no. of shells increases and so the distance of the outer electrons from the nucleus increases
- the bonded pair of electrons are attracted less strogly
Polar covalent bonds?
- if the 2 bonding atoms are different diff elec neg., ethir attraction for the shared pair of electrons is unequal
- more elctronegative atom has a a greater atttraction for the bonded pair of electrons
non polar bonds ?
- if the 2 bonding atoms are the same or have same/similar electronegativity, their attraction for the shared pair of electrons is equal
- the electrons are equally distributed between the bonding atoms
- the bond is PUREcovalent
dipoles?
- the differing attraction for the pair of electrons allows there to be a small charge difference between the atoms
delta pos, delta neg
electron density?
relates to the probability of finding electron at a particular position of space
- can be imagined as a cloud of electrons around a nucleus, like contour lines
spectrum of bonds - ionic
- the diff in electronegativity is so great that one atom effectively takes tehe electrons from another
spectrum of bonds - polar covalent?
- the diff in electronegativity is small
- the atoms share the electrons unequally
- the bond is polarised
spectrum of bonds - covalent?
- no difference in electronegativity
- the molecule is electronically similar
molecules containing polar bonds are not always polar…
the symmetry of polar bonds can cancel out the effect of any permanent dipole
non symmetrical?
- e.g. h20
- a diff in charge exists across the molecule, there is an overall dipole, molecule is polar
symmetrical?
- e.g.CO2
- the symmetry of the molecule means that the effect of any permanent dipole is cancelled out
- linear, tetrahedral or trigonal planar shape
- all atoms attached to central atom are identical
- no diff in charge exists across the molecule
non - polar bond definition?
the 2 bonding atoms are identical and the electrons are equally distributed between the bonding atoms
polar bonds definition?
the 2 bonding atoms are different and their attraction for the shared pair of electrons is unequal
intramolecuar forces ?
act WITHIN molcules
- ionic, covalent
Intermolecular forces ?
forces of attractraction BETWEEN molcules
- non bonded interactions
- don’t involve transfer of electrons
intermolecular forces are the result of?
the constant an random movement of electrons within the shells of atoms