Answer:
AS we move from bottom to top on periodic table shielding decreased.
Explanation:
As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction.
As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.
As we move from bottom to top the energy level decreased because of decreased in electron thus shielding decreased and atomic size also decreased.
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Molar mass of 
<u>As we know</u>–
1 mol =
formula units
1 mol = 143.092 g = formula units
Henceforth –
formula units –
<span>There's a trend in electronegativity. The bottom left of periodic table is the lowest (0.7) and the upper right is the highest (4.0). The most polar is the greatest difference in electronegavity.
hbr- 1~ , hi- 0.5~ ,hcl - 1.3~ , hf-1.8 so,hf is the answer</span>
It would decrease because they will be using less of their AC now that they've improved insulation.
