Bonding, structure and electrons Flashcards
what are the sub shells ?
s - p - d - f
what is spin pairing ?
two electrons in an orbital with opposite ‘spins’
what shape are s orbitals ?
spherical
what shape are p orbitals ?
dumbbell shaped
what to remember with electron configuration ?
4s sub shell has lower energy level than 3d sub shell (so fills first in graph)
why can ionic compounds conduct when molten ?
ions are mobile and able to carry charge
why do ionic compounds have high melting points ?
giant ionic lattices held by strong electrostatic forces which require lots of energy to overcome
why do ionic compounds tend to dissolve in water ?
polar water molecules attract to the charged ions and pull them away from lattice
whats special about boron trifluoride ?
boron has 6 electrons in its shell
whats special about sulfur hexafluoride ?
sulfur has 12 electrons in its shell
what is dative covalent bonding ?
when both electrons in a bond come from the same atom
what to remember with VSEPR theory ?
lone pair of electrons repel more than bonding pair
define electronegativity
an atom’s ability to attract the electron pair in a covalent bond
what are the most electronegative elements ?
fluorine — oxygen, nitrogen, chlorine
what is electronegativity measured on ?
Pauling scale
what makes a bond polar ?
bonding electrons pulled closer towards more electronegative atom
what does the difference in electronegativity between two atoms create ?
permanent dipole
what determines whether the molecule will have an overall dipole (is polar) ?
the arrangement of the polar bonds
if the polar bonds are symmetrical …
dipoles cancel, so no overall dipole so non-polar
if the polar bonds are non-symmetrical …
charge is arranged unevenly, so there is an overall dipole, so is polar
what are the 3 intermolecular forces ?
London forces / permanent dipole - dipole interactions / hydrogen bonding
what are the other names for London forces ?
Van der Waals / induced dipole-dipole
where are London forces present in ?
between all atoms / molecules
simply describe what London forces are
electrons always moving in atom, one side will have
more, creates temporary dipole (which induces dipole on other atoms) - always changing
what increases strength of London forces ?
- larger no. of electrons
- greater contact area
what are permanent dipole-dipole forces ?
weak electrostatic forces of attraction between molecules caused by delta charges on polar molecules
hydrogen bonds can only form when …
covalently bonded to fluorine / nitrogen / oxygen
what is a hydrogen bond ?
weak bond between hydrogen and lone pair of electrons from N, F, O due to the bond being so polarized
why is ice less dense than water ?
water molecules held in a lattice and have more hydrogen bonds in ice
why do simple covalent compounds have low melting / boiling ?
weak intermolecular forces holding together molecules don’t require much energy to break
why are polar molecules soluble in water ?
hydrogen bonds form with water molecules, making it soluble
why don’t simple covalent compounds conduct electricity ?
no charged particles to carry the charge
what must you do to melt / boil and simple covalent compound ?
overcome intermolecular forces (not strong covalent bond)
