3. Periodicity Flashcards
which oxides are basic and which are acidic?
Ionic acids are BASIC
covalent oxides are ACIDIC
Aluminium oxide is … (what kind of oxide is it)
Ionic with covalent character —> AMPHOTERIC
what does the period number correspond with?
the principal quantum number, n
of the highest occupied energy level in the elements
which groups are part of the s-block?
group 1 - 2
which groups are part of the d-block
transition metal groups area idk
which groups are part of the p block
3-8
whcih groups are part of the f block
the 2 rows below
what determines which block an element is placed in?
which orbital it ends on
eg
1s
2s 2s … (d) … 2p 2p 2p 2p 2p 2p
definition of atomic radius
half the distance between the nuclei of neighbouring atoms in the pure element
atomic radius calculation
distance between 2 nuclei / 2
what atomic radius is for :
- noble gas
- non metal
- metal
- van der waal’s radius
- covalent radius
- metallic radius
factors affecting atomic radius 2
- nuclear charge : incr protons, incr electrostatic attraction, pulls electrons towards nucleus
- shielding effect (by inner electrons) : e in inner shells repel valence electrons – incr no. of e in inner shells, incr shielding effect, decr electrostatic attraction, incr dist
how does atomic radius change in elements in terms of periods and groups?
- across period: decr
nuclear charge incr, but shielding effect pretty constant - down group: incr
valence electrons enter new energy level, further from nucleus
what is the difference in ionic radius of cations and anions
cations – SMALLER than parent
- proton number same but fewer electrons – valence more strongly attracted
anions – LARGER than parent
- add electron – incr in repulsion
- have one more occupied shell than cations
anionic radius affected by charge
More negative charge: more elections, repulsion higher = larger
in the spot along the period where it hops from cation to anion the ionic radius JUMPS. why?
anions have one more occupied quantum shell of electrons
DEFINITION of ionisation energy
first ionisation energy:
minimum energy required in REMOVING one mole of VALENCE electrons from one mole of GASEOUS atoms to form one mole of SINGLY POSITIVELY CHARGED gaseous ion
periodic trends in ionisation energy
- incr across period
effective nuclear charge – incr, shielding same, valence closer to nucleus – incr elecstat attraction - decr down group
atomic radii – no. of filled shells incr, atom size incr – incr dist = decr elecstat attraction
whats special about first ionisation energy in periods 2 and 3
grp 13 lower FIE than grp 2
grp 16 lower FIE than grp 15
(Examples on notes pg 14)
electronegativity definition
relative attraction that an atom has for the shared pair of electrons in a covalent bond
what is the Pauling scale
method of calculating electronegativity
electronogativeity of elements
most electroneg is Fluorine (4.0)
top right corner of p.table then in all directions decr
general periodic trends in electronegativity
- incr across period
atoms smaller, nuclear charge incr, shielding same, effective nuclear charge incr – elecstat att incr - decr down group
atoms larger, incr dist betw bonding e and nuclei – decr elecstat att – decr electroneg
definition of electron affinity
first electron affinity is the enthalpy change when 1 mol of gaseous atoms acquires 1 mol of electrons to form 1 mol of singly neg charged gaseous ions
first electron affinity is exo/endo? why?
exothermic for most elements
- electron added, elecstat att between photons in nucleus and electron
- energy released when nucleus attracts electron (similar to bond forming)
electron affinity down a group
less exothermic
- atomic radius incr
- decr att betw nucleus and added electron (brought to a shell further from nucleus)
electron affinity across a period + exceptions
more exothermic (more negative)
- incr effective nuclear charge
- decr atomic radius
- added e more strongly attracted by nucleus
nitrogen (E.A. >0)
- has 3 unpaired e in the 2p sublevel
- incoming e pairs with one in the p-orbital = extra repulsion component
- energy needs to be supplied ti overcoem the inter-e.nic repulsion between the paired
second electron affinity definition
when 1 mole of singly negatively charged gaseous ions aquires 1 mol of electrons to form 1 mol of doubly neg charged gaseous ions
melting involves….
overcoming the forces of attraction betw ions, atoms or molecules
melting depends on… 2
- structure (packing)
- electrostatic forces of attraction betw particles
structure of Li, Be, Na, Mg, Al
giant metallic
- metallic bonds between cations and sea of delocalised electrons
strcutre of B, C, Si
giant molecular
- covalent bonds throughout the entire giant 3-D network structure
across period melting points
rises thru metals and metalloids, drops abruptly for non-metals
melting point in Na to Al (metal) 4
- due to giant metallic structure
- MP incr from Na to Al (metallic bond strength incr – decr in metallic radius, incr in no of e donated)
- elecstat att betw cations and delocalised e INCR
- more e req to break
melting point in Si (metalloid) 3
- higher than na, mg, al
- due to giant molecular structure / giant 3-D network
- high MP due to e req to overcome many strong covalent bonds (structure)
melting point in P to Ar (non metals)
- low melting pt, decr across
- simple molecular strucutre
- attracted by instantaneous dipole - induced dipole forces (less thermal e req to overcome)
- relative molc mass incr = ID-IDF incr
- incr strength of ID-IDF down grp
melting points in noble gases
very low
- instantaneous dipole-induced dipole forces are weak
- down grp, m,bp incr bc more e that are easily polarised
mp and bp down group 1 (alkali metals)
down grp 1
- mp DECR
- strength of metallic bond DECR
- decr in charge density of cations – elecstat att betw cations and deloc e DECR
- less e req to break the weaker metallic bond
mp and bp down grp 17 (halogens)
down grp 17
- mp and bp incr
- incr in electron cloud size – incr polarizability – incr strength of ID-IDF
- more energy req to overcome the incr strength of the forces
alkali metals (1) down the grp:
- atomic, ionic rad
- first ionisation e
- electroneg
- reactivity
- INCR atomic and ionic rad
- DECR first ionisation energy
- DECR electroneg
- INCR reactivity
good reducing agents, low mp, highly reactive
reaction of alkali metal with water and halogens (MEMORISE EQNS)
water –> form alkaline solution + H2 gas
2K (s) + H2O (l) –> 2 KOH (aq) + H2
non metals eg halogens –> ionic compounds
Na (s) + Cl2 (g) –> 2NaCl (s)
halogens (17) down the grp:
- atomic, ionic rad
- first ionisation e
- electroneg
- reactivity
- oxidising strength
- INCR atomic and ionic radius
- DECR first ionisation energy
- DECR electroneg
- DECR reactivity
- DECR oxidising strength
reaction of halogens with alkali metals
Ag+ (aq) + X- (aq) –> AgX
eg
AgCl white, AgBr cream, AgI yellow
displacement reactions of cholrine, bromine and iodine
oxidising strength decr down grp
(chlorine strongest)
eg
Cl2 + 2I- –> I2 (brown ppt) + 2Cl-
