Introduction to Biochemistry - Quiz 1.1.1

Starting this post the results are validated by EDX, so I am sure these answers are correct.

Iron and silicon are available in living organism only for trace amount (arguably - while Iron is in trace amount, it is an important element for human - we need it for hemoglobin). But we have abundant amount of iron and silicon in Earth's crust.

$sp^3$ orbitals are formed by merging the s orbital with 3 p orbitals, therefore we have 4 $sp^3$ orbitals. These 4 $sp^3$ orbital are then used to form 4 different bonds with 4 different atoms.

$sp^3$ orbitals are formed by merging the s orbital with 2 p orbitals, therefore we have 3 $sp^3$ orbitals. These 3 $sp^3$ orbital are then used to form 3 different bonds with 3 different atoms. For one particular bond, the associated $p$ orbital will also overlap and share electrons, that is a double bond.

$sp^2$ orbitals are formed by merging the s orbital with 1 p orbitals, therefore we have 2 $sp^3$ orbitals. These 2 $sp^3$ orbital are then used to form 2 different bonds with 2 different atoms. For on3 particular bond, the other two$p$ orbitals will also overlap and share electrons, that is a triple bond.

First of all $\Delta EN$ is the difference in electronegativity. The $C-C$ bond is obviously neutral. Now, we analyze the electronegativity of $C$, $N$ and $O$, obviously, $O$ is the most electronegative, therefore $O-H$ has the biggest difference in electronegativity.