3.2.1 Periodicity Flashcards
Structure of the periodic table
Group = vertical
Period = horizontal
Periodicity definition
Study of repeated trends in a period
pattern in properties of an element across a period
Atomic radius trends on the periodic table
Atomic radius decreases along a period
As nuclear charge increases and shielding remains constant
Atomic radius increases down a group
As shielding increases which reduces the attraction
Ionisation energy trends on the periodic table
Ionisation energy along a period increases
As the ar is is decreasing and the nuclear charge is increasing
So are held strongly together so more energy is needed to separate
Down a group it decreases
As nuclear attraction decreases as shielding increases less energy needed
Melting point is period 3
increases till si
then drops down for p
then increases up to s
then decreases to cl and ar
cl and p lower than na
s higher than na
Reasons for the different melting points in group 3
Na,mg.al = metal sso have metallic bonding. Increase across as greater positively charged ions. More e released - so electrostatic forces increase
Si - giant covalent - string covalent bonding
P,s,cl - simple covalent - weak van der waals
Ar - very stable as is a full outer shell has weak van der waals
periodic table
list of all known elements in order of increasing atomic mass
lanthandides and actinides
lanthadides - top
are metals which are not often enocountered
acetinindes radiactove metals found in trace quantities
make up f block
trend period 3 react to form
group 1,2,3 - giant ionic compounds - loose there outer electrons to form ionic compound
group 4-si
4 electrons in outer shell meaning 4 covalent bonds - giant covalent
group5,6,7
covalent compounds or ionic compounds
group 0 - full outer shell - uncreative
non metals melting point
vander walls - for molecular
vander walls effected by the number of electrons and how closely they pack together
bonding period 3
na,mg - meatalic bonding
si - macromolecular
p,s,cl - simple molecular
ar - nobal gas
metals melting point
effected by the strength of the metallic bonding
- depends on the sea of delocalized electrons
- charge of the ion
- meaning stronger attraction in lattice
how to measure atomic radius
can only be measured by 2 atoms -has no clear point the electron density drops to 0
ionisation elegy anomalies
AL looses from a higher energy level 3p not 3s
s - outer most electron is paired in p orbital meaning easily removed
why sulfur has a higher melting point than phosphorus
becuase s8 bigger than p4 - larger molecule
meaning more vnader vaal
period 3 highest second ionisation energy
na
Electron (removed) from the 2nd shell / 2p (orbital)
why ionisation energy is endothermic
energy needed to overcome the attraction
between the (negative) electron and the (positive)
nucleus or protons
why second ionization energy is higher than first
(More energy to) remove an electron from a (more)
positive ion / cation
