What is the structure of Basic beryllium Nitrate (BBN)?

Basic Beryllium nitrate is a Covalent compound and has as unique structure like [Be4O(NO3)], containg six nitrate group. The more interesting structure of Basic Beryllium nitrate because the nitrate group act as indented ligand in forming a bridge  between two Be atoms.

How to basic beryllium nitrate is obtained from beryllium nitrates?

Their is a unique feature of Beryllium nitrate , on heating at low temperature (125℃) it give Basic Beryllium nitrate , nitrogen gas and oxygen gas but at high temperature (above 1000℃) it give same products like other bivalent nitrate salts.

Why are the properties of CO2 and SiO2 different?

Their properties are very different because CO₂ is a chain-like three-atom  molecule and SiO₂ is a solid compound with the three dimensional bridges between silicon and oxygen atoms.

Why trimethylamine amine ( N(CH3)3) is tetrahedral while trisilyl amine (N(SiH3)3) planner.?

Nitrogen (N) atom in trimethylamine [N(CH3)3] is sp3 hybridised and tetrahedral due to non bonding electron pair of N is localised (more basic). On the other hand N atom of trisilylamine [N(SiH3)3] is sp2 hybridised and trigonal planner.This is due to the participatlon of non-bondlng pair of N into pπ-dπ back banding. Due to this delocalization of non-bonding electron pair of N in trisilylamine it is also less basic.

What is the Si–N–C bond angle in Silyl isothiocyanate and methyl isothiocyanate (H3CNCS)?

The hybridization of Nitrogen in Methyl isothiocyanate (H₃CNCS) is Sp2. Thus bond angle (< C-N-C) is expected to be 120°. But it is slightly greater than 120° due to resonating structure. The resonating structure has N as Sp hybridized. Hence bond angle of the overall structure is found to be about 142°

But in case Silyl isothiocyanate (SiH₃NCO), the structure is found to be (sp hybridized)