Question

Name or state the following with reference to the elements of the first three periods of the periodic table.
(a)noble gas with duplet arrangement of electrons.
(b)metalloid in period 3.
(c)valency of elements in group 14 and 15.
(d)noble gas having electronic con figuration : 2,8,8.
(e)group whose elements have zero valency.
(f)a covalent compound formed by an element in period 2 and a halogen.
(g)non-metallic element present in period 3 of groups 15 and 16.
(h)an electrovalent compound formed by an adult alkaline earth metal and a halogen.
(i)bridge elements of period 3 of group 1,2 and 3.
(j)alkali metal in period 3 that dissolves in water giving a strong alkali.
(k)typical elements of group 14 and 15.
(l)alkaline earth metal in period 3.

Answer 1

(a) Helium

(b) Metalloid is Silicon

(c) Group 14 = 8 - 4 = 4
Group 15 = 8 - 5 = 3

(d) Argon

(e) Group 18 (Noble gases)

(f) NCl3 or Nitrogen Trichloride

(g) Group 15 is phosphorus
Group 16 is sulphur

(h) Magnesium Chloride

(I) Na, Ca (Diagonal relationship)

(j) Sodium (but it reacts violently with water, causing fire)

(k) Group 14: C, Si, Ge, Sn, Pb
Group 15: N, P, As, Sb, Bi

(l) Magnesium




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Answer 2

a) Helium He
b) Silicon Si
c)In group14 there are 6elements -C
d)Argon Ar has the electronic configuration 2,8,8
e)Group18 has zero valency because their outer most shell is filled.
f)BF3
g)Arsenic As and Selenium Se.
h)MgCl2
i)Mg
j)NaOH
k)Carbon group and Nitrogen group
l)Calcium Ca.
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