Is boron trichloride a Giant covalent or Simple molecular substance

Simple.

BCl3 doesn't involve the element boron in its elemental state.

Compounds are different to their elements.

I don't get what the bit underlined means as boron is in the compound. Thanks

A compound containing an element often bares little resemblance to the pure element itself.

So how do I identify what structure compounds have? In my textbook, it states that element such as carbon, boron and silicon can form giant covalent lattice. But this doesn't apply to co2 and BF3 in this case? Or do I only need to know only diamond, graphite and graphene and SiO4 can ?

Thanks

SiO₂