Question

Which solid has a simple molecular lattice?
A calcium fluoride
B nickel
C silicon(IV) oxide
D sulfur
Okay so i thought lattices need cation and anions so i cancelled out B and D but D is the correct answer how?

Answer 1

Well, let's start by looking at the definition of lattice. Basically, a lattice is an infinite 1,2, or 3-D regular arrangement of points, each of which has identical surroundings. So basically, simple molecular lattices means that the atoms are bonded with very few covalent bonds. Giant molecular lattices, which is the opposite, are made of atoms bonded together with many many strong covalent bonds.

Answer 2

Now, it takes alot of energy to break a giant molecular lattice, because there are so many strong bonds to break. This causes the boiling and melting points to be extremely high. However, in a simple molecular lattice, the boiling and melting points are very low, because not much energy is required to break the few bonds.

With this being said, lets look at the boiling and melting points of each substance, and that should give us our answer.

Answer 3

Here's a little table of them.

Melting Boiling
2,584°F 4,591°F calcium fluoride
2,651°F 4,046°F °F nickel
2,912°F 4,046°F silicon (IV) oxide
239.4°F 832.4°F sulfur

Notice how sulfur's melting and boiling points are WAY lower than the rest? This shows that sulfur, is indeed, a simple molecular lattice.

Answer 4

Wow nice explanation but i won't get table for my exam so is there any other way to tackle this type of mcq?

Answer 5

Is this right if i say Sulphur is a nonmetal so it has low melting point while Ni being a transition metal will have high melting point? So sulphur will have a simple molecular lattice ?

Answer 6

Phosphorus, sulfur, chlorine and argon are the only elements which only have one force of attraction between them, so these four are the only simple molecular elements. Just memorize these and you'll be set.

Answer 7

Thanks so much.

Answer 8

So what structures are A and C anyway?

Answer 9

Anytime :) But I believe they are giant molecular compounds

Answer 10

Ohkay!

Answer 11

My bad! Silicone, graphite, diamond and silicone oxide are the only four giant molecular compounds! I believe calcium fluoride is just a regular old ionic compound.

Answer 12

No problem. I always believed only ionic compounds have lattices so i got confused when i saw the answer.