<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.
Answer:
calcium chloride deihydrate
Answer:
a. alkyne
b. alkane
c. alkyne
d. alkene
Explanation:
The general formula for each class of compound is given below
Alkane: 
Alkene: 
Alkyne:
(assuming single multiple bonds)
Now let us classify according to the above formulas:
a. It has two hydrogen atoms less than the two times of carbon atoms hence, it's alkyne
b. It has two hydrogen atoms more than the two times of carbon atoms hence, it's alkane
c. It has two hydrogen atoms less than the two times of carbon atoms hence, it's alkyne
d. It has hydrogen atoms two times of carbon atoms hence, it's alkene
Just like how heat moves from a region of higher
temperature to a region of lower temperature, molecules also tend to move from
a region of higher concentration to a region of lower concentration. This is
called natural diffusion and is naturally happening to reach stability.