s and p Flashcards
why are they called s block elements
valence electrons present in s block
why they called p block elements
group 3a to 8a elements except helium.
valence electrons in p block
f block elements
lanthanides and actinides. valence e in f block
Classification of elements in blocks is based on the:
A.Ease of removal of electron
B.Ease of gain electron
C.Number of electrons present in the valence shell
D.Valence orbital of the element involved in chemical bonding
D.
Classification of elements in blocks is based on the valence orbitals of the elements involved in chemical bonding. Elements are classified into four blocks: i. s-block ii. P-block iii. d-block iv. f-block
assumptiions for measuring atomic size.
- atoms assumed as spherical
2.size of atoms expressed in terms of atomic,ionic and covalent radii
Methods of measuring atomic radius
distance bw centres of adjacent atoms by
. xrays
.spectroscopy
.electron diffraction
why cant atomic radius be determined precisely
- no sharp boundary of an tom.
2.electronic probability distribution is affected by neighbouring atoms.
atomic radii trend
1.decreases from left to right in a period.
due to;
increase in nuclear charge
sheilding remains same from left to right
2.increases from top to bottom
due tp;
increase in shells
increased shielding
ionic radii (cationic and anionic)
- catonic radius smaller than parent atom.
.shell may be removed
.eff nuclear charge increases
2.anionic radii larger than parent (cl to cl-)
.atom expands its valence shell
isoelectronic species
cations of any period have similar number of electrons(are isoelectronic to each other)
similarly anions do this too(also isolelectronic to noble gases)
covalent radii trend
left to right decreaase
top to bottom increase
(almost same as atomic radi)
ionisation energy
min energy req to remove an electron from its gaseous atom to form ion
ionisation energy trends
along the group
.decreases top to bottom
along the period
increases from left to right
factors affecting ionisation energies(4)
- I.E inersely propotional to atomic radius
- I.E directly propotional to nuclear charge
- I.E inverse with sheilding
- penetration effect direct relation with I.E
sheilding effect across the period?
remains constant.
(down the group becomes stronger. along the period has same shell)
reverse of ionisation energy process is called
electron affinity
which group of elements have the highest I.E
group VIIIA or noble gases
electron affinity
energy released when an electron adds to empty or half filled orbital of a gas atom to form an anion 1- ion.
first ea always exo -
second always endo +
trends of e.a
decreases down the group
increases left to right
why fluorine’s E.A is less than that of chlorines
F2 is small and have 7 electrons in 2s and 2p subshells which have a thick electron cloud(which repels incoming electrons.)
which groups have abnormal trend of E.A(low ea) in every peroid
group 2a, 5a and 8a.(hence, halogens have highest ea)
(2a)metals love to lose e- not gain
(5a) have half filled p shell
(8a) have filled valence shell.[doesnt need.]
bond formed bw elements of low i.e and high e.a.
ionic.
low i.e=metals
high ea=non metals.
electronegativity
tendency of an atom to ATTRACT A SHARED ELECTRON PAIR to itself.
electron affinity trends with reasons
- decreases down the group
(increase in atomic size and sheilding efect)
2.increases from left to right
(decrease in atomic size and sheilding constant)
