module 3 periodicity Flashcards
periodicity
repeating trend in properties across each period
ionisation energy state
gaseous
first ionisation energy
energy needed required to remove one e- from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
first ionisation energy equation
Mg(g) -> Mg+(g) + e-
value of each successive ionisation energy
increases
e- drawn slightly closer to nucleus
successive ionisation energies provide evidence for
shells
a large difference in ionisation number shows
change in energy level
new shell closer to nucleus
therefore harder to remove
trends in first ionisation energy down group
atomic radius increases
shielding increases
attraction decreases
trends in first ionisation energy across period
nuclear charge increases
atomic radius decreases ( contraction)
shielding constant
falls across periods (ionisation energy) group 2 and 3
group 3: 3p subshell, higher energy
group 2: 3s
3p lost more easily than 3s
falls across periods (ionisation energy) group 5 and 6
group 5: unpaired
group 6: e- lost from orbital containing paired e-
paired e- repel more, lost more easily
metal structure
giant lattice
metallic bonding
+ve metal ions
-ve delocalised e-
electrostatic forces
why conduct?
moving charged particles (mcps)
why do ionic compounds not conduct when solid?
ions fixed in lattice
diamond structure
tetrahedral
graphite structure
planar
weakly held together
diamond and silicon
do not conduct
graphite and graphene
conduct
melting points
*increase for metals in same period
as you go across more highly charged ions and more delocalised e-
*giant covalent structures (B,C,Si) highest mp due to strong covalent bonds
*for simple molecules mp depends on London forces so no of e-
