Explain why naturally occurring minerals in rocks often have a visible crystalline structure.

With a definite chemical composition (every time we see the same mineral it has the same chemical composition that can be expressed by a chemical formula). and a characteristic crystalline structure (atoms are arranged within the mineral in a specific ordered manner).

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1) Answer is: A triple bond, because they overlap orbitals to share three pairs of electrons.

Nitrogen (N) is in group 15 of Periodic table of elements and his atomic number is seven, which means that nitrogen has seven electrons and electron configuration: ₇N 1s²2s²2p³.

Nitrogen is inert (low reactivity) nonmetal and has five valence electrons. Nitrogen has oxidation numbers from -3 to +5.  

Nitrogen molecule (N₂) has strong nonpolar triple covalent bond (:N:::N:), that is why it is very stable and have low reactivity.

In molecule of nitrogen (N₂), bond order is 3 , because there are three pair of electrons (6 electrons) between nitrogen atoms.

2) Answer is: It is the sharing of electrons by overlapping orbitals.

For example, in molecule of ammonia NH₃, three sp3 orbitals of nitrogen  atom overlaps with 1s of three hydrogen atoms and form three sigma covalnt bonds.

Electron configuration for nitrogen: ₇N 1s² 2s² 2p³.

Electron configuration for hydrogen: ₁H 1s¹.

The central atom in ammonia, nitrogen, is sp3 hybridized (one s and three p-orbitals will combine for a four sp3 hybridized orbitals), because sp3 orbitals have lower energy.

3) Answer is: True.

Covalent bond is bond between nonmetals.

For example, molecule carbon monoxide CO has covalnet bond.

Carbon (C) and oxygen (O) are nonmetals.

Carbon atom and oxygen atom are connected by a triple bond (six shared electrons in three bonding molecular orbitals) that is formed of two covalent bonds and one dative covalent bond.

Dative covalent bond is formed by two electrons derive from the oxygen atom.

Carbon monoxide is a colorless, odorless, toxic and tasteless gas.

4) Answer is:  Only Student A.

When determining the best Lewis structure for a molecule, the structure is chosen such that the formal charge (FC) on each of the atoms is as close to zero as possible.

Formal charge (FC) estimates the distribution of electric charge in a molecule.

The formal charge of any atom in a molecule can be calculated with the equation: FC=V-N-B/2.

V is the number of valence electrons of the neutral atom in ground state.

N is the number of non-bonding valence electrons on atom in the molecule.

B is the total number of electrons shared in bonds with other atoms in the molecule.

Oxygen atom has two non-nonding pair of electrons and two valence electrons shared in bonds.

The bond bewteen oxygen anf hydrogen is poalr sigma covalent bond.

5) Answer is: True.

In chemical compound CH₂O there is two single bonds bonds between carbon atom and hydrogen atoms and one double bond between carbon atom and oxygen atom.

Both carbon and oxygen have sp2 hybridization in this carbonyl group.

Carbon has three sigma bonds with sp2 orbitals and oxygen has one sigma bond with sp2 and two free electron pairs with sp2 orbitals.

Pi bonds are formed between two p orbitals.

6) Answer is: Compound D is covalent because both atoms are in need of electrons.

Atom is most stable when it has full filled electron shell with electromns like closest noble gas.

Atoms in combound D need electrons, first atom two and second atom three electrons, to form stable electron configuration as closest noble gas, so they share electrons.

Compound C is probably ionic compound.