Problem: The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound. (A) HS (B) HS2 (C) H2S (D) H3S2

FREE Expert Solution

We are being asked to determine the molecular formula for hydrogen sulfide based on the valence electrons of sulfur

Sulfur is in Group 6A and has 6 valence electrons and would only need two electron groups/atoms to satisfy an octet.

Hydrogen on the other hand has 1 valence electron and would need to bond with a single atom to satisfy the octet.

Recall that the octet rule states that an element is surrounded by eight electrons in the Lewis structure. 


Exceptions to this rule occur when:

• there is an odd number of electrons, like in radicals

• there are less than 8 electrons or incomplete octet

• there are more than 8 electrons or expanded octet. This occurs to nonmetals from Period 3 to 7.


For this problem, we are dealing with charged species that form ionic compounds.

Elements have common charges based on what group they belong to in the periodic table.

Elements gain and lose electrons so that they have the same number of electrons as the noble gases (Octet Rule).


Metals → lose electrons and gain positive (+) charge to become more like their closest noble gas


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Problem Details

The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound. 

(A) HS 

(B) HS2 

(C) H2

(D) H3S2

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Ionic and Covalent Bonds concept. If you need more Ionic and Covalent Bonds practice, you can also practice Ionic and Covalent Bonds practice problems.