Unknown element W has 2 valence electrons. Unknown element X has 7 valence electrons. Which formula shows the most likely outcome when elements W and X react?
A
WX
B
WX2
C
W2X
D
W2X2
The answer is B. WX2.
Element W has 2 valence electrons, so it is likely to lose those electrons and form a positive ion with a charge of +2.
Element X has 7 valence electrons, so it is likely to gain 1 electron and form a negative ion with a charge of -1.
To achieve stability, element W will need to transfer its 2 valence electrons to element X. This will result in W losing 2 electrons and X gaining 2 electrons, forming W2+ and X2- ions.
To balance the charges, we need 2 X ions for every 1 W ion. Therefore, the most likely outcome when elements W and X react is the formula WX2.