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Question:
I can't get this question. It doesn't make any sense.
In Elmo’s world, the study of chemistry is just beginning.  It is a much simpler world with only a few elements.  The Journal of the Elmo Chemical Society reports the following compounds have been created: Q2E; QP; WX; WP2; Z2D; AV; and SX.  Elmo has been unable to make any compounds with element T or with element G.  Elmo has also determined the atomic masses of all the known elements.

Element
A
B
X
D
E
G
Q
P
S
T
V
W
Z
Atomic Mass
6.7
16.8
14.6
9.0
3.4
11.2
1.1
4.5
7.9
5.6
15.7
2.2
12.4

Elmo and his friends now need your help in building a Periodic Table and suggesting new areas of research.

First, consider the data on atomic masses and on the compounds which have been made.  (Since they are just beginning, some elements may not have been discovered yet.)  Make a Periodic Table for Elmo’s world. Leave gaps where necessary for elements which are not yet discovered.

Second, explain to Elmo how the table you made is arranged.

Third, suggest the formula for compounds made from A and X, from S and E, from A and P, and from B and Z.



ANSWER


Elements could be arranged on the basis of 1) similar chemical property
Here elements having similar combining capacity (or valency ) have similar properties,they must be grouped together.
Also,1) periodicity in arranging elements in the order of increasing atomic masses could be considered to arrange the elements
T,G=noble element (forms no compound)
Q2E and QP shows valency  of Q=+1 ,E=-2,P=-1
WX,WP2 suggests W=+2 (P=-1) ,X=-2
SX suggests S=+2 (since X=-2)
Z2D , Z=+1 ,D=-2
AV= A=+3, V=-3 (as they are not shown in combination with any other element)
Groups
period
1(+1 valency)
2(+2 valency)
3 (+3)
4(0)
5(-3)
6(-2 valency)
7(-1)
8(noble)

Q (1.1)
W(2.2)



E(3.4)
P(4.5)
T(5.6)

A (6.7)
S(7.9)
Not discovered
-
Not discovered
D(9.0)
-
G(11.2)

Z(12.4)
-
-
-
-
X(14.6)
V(15.7)
B(16.8)



















c) A and X
A(+1)   X(-2)=A2X
 S (+2) and E(-2)= SE
A(+1) and P(-1)=AP
B and Z= no compound (0) noble


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