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24 ICSE Chemistry – 10
Q 27. )KXG C TGCUQP HQT GCEJ QH VJG HQNNQYKPI [ICSE 2018]
K +QPKUCVKQP RQVGPVKCN KPETGCUGU CETQUU C RGTKQF HTQO NGHV VQ TKIJV
KK #NMCNK OGVCNU CTG IQQF TGFWEKPI CIGPVU
Q 28. +P 2GTKQF QH VJG 2GTKQFKE VCDNG GNGOGPV $ KU RNCEGF VQ VJG NGHV QH GNGOGPV # [ICSE 2018]
On the basis of this information, choose the correct word from the brackets to complete the following statements:
K 6JG GNGOGPV $ YQWNF JCXG NQYGT JKIJGT OGVCNNKE EJCTCEVGT VJCP #
KK 6JG GNGOGPV # YQWNF RTQDCDN[ JCXG NGUUGT JKIJGT GNGEVTQP CHſPKV[ VJCP $
KKK 6JG GNGOGPV # YQWNF JCXG ITGCVGT UOCNNGT CVQOKE UK\G VJCP $
Let us say it Again
Dobereiner’s triads. The atomic mass of the middle element of a Dobereiner's triad is equal to the arithmetic mean of
the other two elements.
Newlands’ law of octaves. The properties of each element resembled those of the eighth element before it and of the
eighth element following it. or
The properties of the elements were or repeated at every eighth element like the eighth note of an octave in music.
Mendeleev’s periodic law. Mendeleev’s periodic law states that “the properties of the elements are a periodic function
of their atomic masses.”
Moseley found that the atomic number is a more fundamental property than atomic mass.
Modern periodic law. The modern periodic law states that “the properties of the elements are the periodic function of
atomic number.”
Long form periodic table. The original long form periodic table was designed by Böhr in 1920.
Periods. The horizontal rows of elements in the periodic table are called periods.
Groups. The vertical columns of elements in the periodic table are called groups.
Elements belonging to the same group have the same number of valence electrons, show the same valency, and show
similar chemical behaviour.
In the long form periodic table as modified by IUPAC the groups are numbered from 1 to 18.
The number of elements in each period of the long form of the periodic table is equal to the number of electrons in the
corresponding electron shell.
Periodicity in a group. In a group, the atomic size or atomic radius, and metallic character increase, while the
electronegativity, and ionisation energy decrease in going from top to bottom of the group.
Periodicity in a period. In a period, the number of valence electrons, electronegativity and ionisation energy increase,
while atomic radius (or size), metallic character, and the basic nature of the oxides, decrease in going from left to right.
Variation in the properties of elements in a group and in a period of the periodic table are summarized as follows:
In a Period
Ŗ #VQOKE PWODGT Increases
Ŗ #VQOKE UK\G QT TCFKWU Decreases In a Group
Ŗ 0Q QH XCNGPEG GNGEVTQPU Increases Ŗ #VQOKE PWODGT Increases
Ŗ 8CNGPE[ Increases Ŗ #VQOKE UK\G QT TCFKWU Increases
then decreases Ŗ 0Q QH XCNGPEG GNGEVTQPU Remains same
Ŗ 6GPFGPE[ VQ NQUG GNGEVTQPU Decreases Ŗ 8CNGPE[ Remains same
Ŗ 6GPFGPE[ VQ ICKP GNGEVTQPU Increases Ŗ 6GPFGPE[ VQ NQUG GNGEVTQPU QT Increases
Ŗ /GVCNNKE EJCTCEVGT Decreases metallic character
Ŗ 0QPOGVCNNKE EJCTCEVGT Increases Ŗ 6GPFGPE[ VQ ICKP GNGEVTQPU QT Decreases
Ŗ 0CVWTG QH QZKFGU Basic to acidic nonmetallic character
Ŗ %JGOKECN TGCEVKXKV[
of metals Increases
of nonmetals Decreases
