Answer:
A = shielding.
Explanation:
The addition of electron causes the atomic size increase from top to bottom due to increase in atomic number.
As the atomic number increased one more electron is added and because of this electron on more electronic shell is added. Thus the electron become more away from the nucleus as many of other electrons are present in the way from nucleus to the outer electrons.
The hold of nucleus becomes weaker. Although nuclear charge is also increased but at the same time other electrons shield the respective electrons. So effective nuclear charge is weaker than the actual nuclear charge.
Because of this shielding it is easy to remove the electrons or we can say ionization energy decreases.
The answer is b because it could happen to you
½H2(g) + ½I2(g) → HI(g) ΔH = +6.2 kcal/mol
or...
½H2(g) + ½I2(g) + 6,2kcal/mole → HI(g)
________
21.0 kcal/mole + C(s) + 2S(s) → CS2(l)
or...
C(s) + 2S(s) → CS2(l) ΔH = +2,1 kcal/mole
_________
ΔH > 0 ----------->>> ENDOTHERMIC REACTIONS
No, don't try, it will explode close to 187 kPa
