<u>Answer: </u>The correct statement is X is the effective nuclear charge, and it increases across a period.
<u>Explanation:</u>
We are given that:
X = number of protons − number of core electrons
Effective nuclear charge is defined as the actual nuclear charge (Z = number of protons) minus the screening effect caused by the electrons present between nucleus and valence electrons. These electrons are the core electrons.
The formula used for the calculation of effective nuclear charge given by Slater is:

where,
= effective nuclear charge
Z = atomic number or actual nuclear charge or number of protons
= Screening constant
The effective nuclear charge increases as we go from left to right in a period because nuclear charge increases with no effective increase in screening constant.
Hence, the correct answer is X is the effective nuclear charge, and it increases across a period.
Take the molality and multiply it by the Kb
0.75 × 0.52 = 0.39 C
then add the boiling pt to the 0.39
100 + 0.39 = 100.39 C
Answer:
(a) The lewis structure for methylisocyanate is in the attached.
(b) The carbonyl carbon have an sp² hybridization
(c) The nitrogen have an sp² hybridization?
Explanation:
(a) The lewis structure for methylisocyanate has the nitrogen with one lone pair and the oxygen with two lone pairs.
(b) The carbonyl carbon form double bond with the oxygen causing to form three hybrid orbitals sp².
The Nitrogen also forms a double bond with the carbon having an sp² hybridization too.