Question

B. Ionization enthalpy of Li is 520 kJ mol
while that of Fis 1681 kJ mol. Explain.​

Answer 1

Answer:

Variation in valencies.

Explanation:

Li is an alkali metal with an atomic no. of 3. To obtain a stable orbit, it must form a duplet, i.e., lose 1 electron to form Li+ atom having 2 electrons, so its ionization enthalpy is less.

F on the other hand is an electronegative atom with an atomic no. of 9. To obtain a stable orbit, it must gain 1 electron, thus completing its octet and forming F- ion.

Now, if you try to remove an electron from F atom instead, that would disturb its octet even more and a large amount of energy will be required to achieve this, hence the larger value of ionization enthalpy.

Answer 2

Answer:

Explanation:

Li and F both are across the period 2. In a period the screening is the same but the effective nuclear charge increases . As a result the outer most electron is held more tightly. The 1st ionization enthalpy , therefore, increases across a period