periodicity Flashcards
atomic radius trends
INCREASE DOWN the group
DECREASE ACROSS a period
atomic radius trend in a group & explain
radius INCREASE down the group
electrons occupied another energy level
valence electrons further from nucleus
[make specific]
atomic radius trend across the period & explain
radius DECREASE across the period
nuclear charge increase (with increasing number of proton)
all valence electrons in the same energy level
similar screening/shielding effect (same number of inner shell electrons)
valence electron experience stronger attractive force from the nucleus and gets pulled in
decrease atomic size
ionic radius: cations
predict whether Na or Na+ is larger in size
Na
what is effective nuclear charge
inner electron SHIELDS outer electrons from the nucleus
outer electron does not feel the full nuclear charge
attractions reduced by electron-electron repulsion
net nuclear charge felt → effective nuclear charge (Z eff)
(nuclear charge - number of inner shell electrons)
ionic radius trend in group & explain (both anion and cation)
INCREASE down the group
(has more occupied electron shells)
valence electrons are further from nucleus
ionic radius trends
INCREASE DOWN the group
ionic radius: cations
predict whether S or S2- is larger in size
S2-
ionic radius trends: size of cations & reason
cations are smaller than original neutral atom
main reason [1]: cation has one less occupied electron shell
has greater net positive charge/same number of protons pulling smaller number of electrons
smaller shielding effect
electron held more tightly
ionic radius trends: size of anions & reason
anions are bigger than original neutral atom
has greater net negative charge/same number of protons
electron held less tightly
TREND: increase down the group; has more occupied electron shells
ionic radius trends: across the period
CATIONS
decrease from group 1-14
isoelectronic (identical configuration), but increase in nuclear charge
ANIONS
decreased from group 14-17
isoelectronic, but increase in nuclear charge
is cation smaller or larger than anions & why?
SMALLLER
cation: 1 occupied electron shell
anion: 2 occupied electron shell
difference in size, bc cation have one less occupied electron shell
ionization energy (1st IE)
energy required to remove one mole of electron from one mole of gaseous atoms
X (g) → X+ (g) + e-
Is (1st) IE endothermic or exothermic
endothermic, bc IE is positive
bond breaking
bond between valence electron and nucleus is broken
ionization energy trends: in a group & explain
DECREASE DOWN a group
increase in the number of occupied electron shell
valence electron further away from nucleus
less attraction to the nucleus
ionization energy trends: across period & explain
INCREASE ACROSS period
increasing number of protons (nuclear charge)
electrons are added to the same shell
SIMILAR SHIELDING effect from inner electons
stronger attraction
[shielding = repulsion]
why is there a drop in ionization energy from Be to B?
**GROUP 2 & 13
p orbital (2p?) is a higher orbital so electron is further from nucleus
weaker attraction
less energy needed to break the interaction
why is there a drop in ionization energy from N to O?
**GROUP 15 & 16
N: electrons fill up p sub-levels and are unpaired
O: paired electrons in p sub-level
more electron-electron repulsion
easier to remove valence
lower IE
is electron affinity (1st) endothermic or exothermic?
exothermic
bond forming
when a metal forms an anion
electron affinity
energy change when one mole of electron is attached to one mole of natural atoms in gaseous state
X (g) + e- → X- (g)
electron affinity trends
DECREASES DOWN a group
INCREASES ACROSS a period
electron affinity trends: in a group & explain
DECREASES DOWN a group
increase in the number of occupied electron shell
valence electron further away from nucleus
less attraction to the nucleus
[most 1st EA values are negative]
become less negative down the group
electron affinity trends: across period & explain
INCREASE across period [values become more negative]
increasing umber of protons/increasing nuclear charge
electrons are added to the same shell
similar shielding effect from inner electrons
stronger attraction
does Si or P have a more negative EA?
P (group 15): less negative than expected
[Ne] 3s2 3p3
electron gained will be paired up in 3p sub level, more electron-electron repulsion
Si
electron config
if add 1 electron to P, it becomes 3p4, have paired electrons = more repulsion
in Si – remain 3p3 singlely filled
does Li or Be have a more negative EA?
Be (group 2) less negative than expected
[He] 2s2
electron gained will be put into 2p sub level
2p sub level further away from nucleus
reduced attraction to nucleus with increased shielding
???
supposedly Be
(beryllium has a lower electron affinity compared to lithium)
Be: add into new sublevel?, further from nucleus
Li: 1s2 2s1
Be: 1s2 2s2
is 1st EA positive or negative?
negative
electron is added to the outermost shell
the attraction between the nucleus and the electron leads to a decrease in energy of the system
is 2nd EA positive or negative?
positive
there is repulsive force between the anion and the negatively charged electron
electronegativity
ability of an atom to attract shared pairs of electrons (do not accept singular) in a covalent bond
what does high electronegativity mean?
pulls the electron pair towards it
electronegativity trends
DECREASES DOWN the group
electronegativity trends: in a group
DECREASES down the group
going down the group:
increasing atomic radii (down the group)
shared pair of electrons (must specify which electron) is further away from nucleus
increase shielding effect
less attraction for the shared pair of electrons
electronegativity decreases
electronegativity trends: across period
INCREASES across period
going across the period:
increasing number of protons/increased nuclear charge
similar shielding effect from inner electrons
stronger attraction
electronegativity increases
which of the following properties of the halogens increase from F to I?
a. atomic radius
b. melting point (& boiling point)
c. electronegativity
A and B (mp and bp increase)
- state and explain the trends in the atomic radius and ionization energy
for the period 3 elements Na to Cl [4]
atomic radius decreases [1]
because nuclear charge increases AND electrons are added to the same main (outer) energy level [1]
ionization energy increases [1]
bc nuclear charge increases AND the electron removed is closer to the nucleus/is in the same energy level [1]
melting point trends: metal
DECREASE DOWN group
atomic/ionic radius increases
smaller charge density OR force of attraction between metal ions and delocalised electrons decreases
weaker metallic bonds
melting point trends: non-metal
INCREASE DOWN group
molecular mass increase (van der waal force increase)
**except group 14 (carbon is giant covalent structure)
metal trends: ionic radius across period
metal ionic radius decrease across period
metallic bond more strong
smaller ionic radius
more delocalised electron
non-metal trends: ionic radius across period
no obv trend
depends on structure & size of molecule
structure: some form polyatomic instead of diatomic
size: bigger more van der waal force
metallic/non metallic behaviour:
why does metal conduct electricity?
low ionization energy / more electronegativity
valence electron can become delocalised
metallic/non metallic behaviour:
why metal forms cation?
low ionization energy
metallic/non metallic behaviour:
why non-metals form anions?
negative electron affinity
exothermic reaction
energy released in bond forming is more than energy needed in bond breaking
reactivity of alkali metals
what ions do they form when they react?
form 1+ ions
reactivity increases down the group
IE decrease down group
valence electrons further from nucleus
easier to remove valence electrons
displacement of halides
a solution of more reactive halogen, X2, reacts with a solution of halide ions, X-, formed by a less reactive halogen
how can the color from displacement of halides be differentiated?
by adding in organic solvent
across period 3: bonding w oxygen
bonding: ionic to covalent across
difference in electronegativity decreases
metal oxides are either
basic or amphoteric
non-metal oxides are either
acidic or neutral
give than Na2O can react with H2SO4 (aq), what can be deduced?
it is basic
need to do 2 experiments: carry out another experiment to show it cannot react with a base
across period 3: acidity of oxides
group 1 & 2: hydroxides considered strong
aq hydrogen involved with acidity
is SiO2 soluble in water?
no, insoluble
acidic, reacts with alkali
SiO2 + 2NaOH –> Na2SiO3 + H2O
is Al2O3 soluble in water?
no, insoluble
how to test amphoteric substance?
react with acid and base + suggest reagent (SPECIFIC)
amphoteric
behaves as an acid or a base depending upon the reaction it is involved with
react with acids AND bases
is aluminium oxide amphoteric?
yes
give the equation of the reaction between aluminium oxide and hydrochloric acid
Al2O3 (s) + 6HCl (aq) –> 2AlCl3 (aq) + 3H2O (l)
reacts with a strong acid to make a salt with water
give the equation of the reaction between aluminium oxide and sodium hydroxide
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) –> 2NaAl(OH)4 (aq)
reacts with a strong base to form sodium aluminate