# 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

 Element Atomic Mass Stable Compound Be 9 BeCl2 S 32 H2S F 19 F2 Ca 40 CaCl2 Li 7 LiCl Si 28 SiH4 Cl 35.4 Cl2 B 10.8 BH3 Ge 72.6 GeH4 N 14 NF3 O 16 H2O Ga 69.7 GaH3 As 75 AsF3 C 12 CH4 K 39 KCl Mg 24.3 MgCl2 Se 79 H2Se Al 27 AlH3 Br 80 Br2 Na 23 NaCl

.

What stable compound might the missing element form?

a) XF4

b) XF3

c) X2F3

d) XF