Problem: The table shown here includes data similar to those used by Mendeleev when he created the periodic table. On a small card, write the symbol, atomic mass, and a stable compound formed by each element. Without consulting a periodic table, arrange the cards so that atomic mass increases from left to right and elements with similar properties are above and below each other. Copy the periodic table you have invented onto a piece of paper. There is one element missingElementAtomic MassStable CompoundBe9BeCl2S32H2SF19F2Ca40CaCl2Li7LiClSi28SiH4Cl35.4Cl2B10.8BH3Ge72.6GeH4N14NF3O16H2OGa69.7GaH3As75AsF3C12CH4K39KClMg24.3MgCl2Se79H2SeAl27AlH3Br80Br2Na23NaCl.What stable compound might the missing element form?a) XF4 b) XF3c) X2F3 d) XF

FREE Expert Solution

Recall that group number = number of valence electrons

  • N has 3 valence electrons → missing element has same characteristics as N (same column) 


--------------Metals---------- -----------------------------nonmetals--------------------------------------- 

Li 7

      Be  9

B 10 .8

C 12

N 14

O 16

F 19

Na 23

Mg 24.3

Al  27

Si 28

X

S 32

Cl 35.4

K 39

Ca 40


Ge 72.6

As 75

Se 79

Br 80


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Problem Details
The table shown here includes data similar to those used by Mendeleev when he created the periodic table. On a small card, write the symbol, atomic mass, and a stable compound formed by each element. Without consulting a periodic table, arrange the cards so that atomic mass increases from left to right and elements with similar properties are above and below each other. Copy the periodic table you have invented onto a piece of paper. There is one element missing


ElementAtomic MassStable Compound
Be9BeCl2
S32H2S
F19F2
Ca40CaCl2
Li7LiCl
Si28SiH4
Cl35.4Cl2
B10.8BH3
Ge72.6GeH4
N14NF3
O16H2O
Ga69.7GaH3
As75AsF3
C12CH4
K39KCl
Mg24.3MgCl2
Se79H2Se
Al27AlH3
Br80Br2
Na23NaCl

.

What stable compound might the missing element form?

a) XF4 

b) XF3

c) X2F3 

d) XF

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