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14 ICSE Chemistry – 10
Thus, the value of electronegativity of an element describes the
ability of its atom to compete for electrons with another atom to which
KV KU DQPFGF (QT GZCORNG KP *%N OQNGEWNG VJG UJCTGF RCKT QH GNGEVTQPU
NKG OQTG VQYCTFU %N 6JGTGHQTG EJNQTKPG KU OQTG GNGEVTQPGICVKXG VJCP
J[FTQIGP
6JG GNGEVTQPGICVKXKV[ ECP DG GZRTGUUGF QP C PWODGT QH UECNGU 6JG
most commonly used scales are due to Pauling (1932) and Mulliken
2CWNKPI CUUKIPGF C XCNWG QH VQ VJG GNGEVTQPGICVKXKV[ QH ƀWQTKPG (
CPF ECNEWNCVGF VJG XCNWGU HQT QVJGT GNGOGPVU 2CWNKPI U GNGEVTQPGICVKXKV[
XCNWGU HQT UQOG GNGOGPVU CTG RTGUGPVGF KP 6CDNG
Table 1.2 Pauling’s electronegativity values for some s and p block elements
Element H Li Na K Rb Cs
Electronegativity
Element Li Be B C N O F
Electronegativity
Factors Affecting Electronegativity
The electronegativity values are affected by the following factors:
Atomic size. The tendency to attract the bonding electrons towards
KVUGNH KPETGCUGU YKVJ C FGETGCUG KP VJG UK\G QH VJG CVQO 6JGTGHQTG
smaller atoms have higher electronegativity values than the larger
atoms +V KU HQT VJKU TGCUQP VJCV VJG GNGEVTQPGICVKXKV[ FGETGCUGU KP IQKPI
from lithium (atomic radius: 152 pm), to cesium, (atomic radius:
RO
Number of inner shells. The atom with larger number of inner shells
has lower value of electronegativity than the atom with lesser number
QH KPPGT UJGNNU
This is because the atom with more inner shells will be bigger than
VJG CVQO JCXKPI NGUUGT PWODGT QH KPPGT UJGNNU 6JG bigger atom
exhibits lower GNGEVTQPGICVKXKV[
+QPKUCVKQP GPGTI[ CPF GNGEVTQP CHſPKV[ Higher ionisation energy
CPF JKIJGT GNGEVTQP CHſPKV[ NGCF VQ JKIJGT GNGEVTQPGICVKXKV[ +V KU FWG
to this reason that the elements of halogen family have the highest
XCNWGU QH GNGEVTQPGICVKXKVKGU
Nuclear charge. )TGCVGT VJG PWENGCT EJCTIG JKIJGT KU VJG
GNGEVTQPGICVKXKV[ 6JKU KU DGECWUG JKIJGT PWENGCT EJCTIG ECP CVVTCEV
GNGEVTQP OQTG UVTQPIN[
Periodic Variation of Electronegativity
8CTKCVKQP QH GNGEVTQPGICVKXKV[ CETQUU VJG RGTKQFKE VCDNG KU FGUETKDGF DGNQY
How does electronegativity vary in a group
Electronegativity of elements decreases down the group.
Explanation: The increase in atomic size reduces the tendency
VQ CVVTCEV VJG UJCTGF RCKT QH GNGEVTQPU 6JGTGHQTG VJG GNGEVTQPGICVKXKV[
FGETGCUGU FQYP VJG ITQWR 6JG GNGEVTQPGICVKXKVKGU QH CNMCNK OGVCNU CPF
halogens are given below:
