Option 1 says that Ionization potential decreases along a period. This is incorrect as Ionisation potential tends to increase along a period. This is because an increased nuclear charge pulls the outer most electrons closer to the nucleus, making it harder to remove them.

Option 2 claims that in a group of elements, electron affinity decreases as atomic weight increases. This is generally true. As you proceed down a group, elements have a lesser tendency to attract a bonding pair of electrons. That`s because the increased atomic weight means electrons are further from the nucleus and not attracted as strongly.

Option 3 asserts that in a given period, electronegativity decreases as atomic number increases. This is not true. Electronegativity generally increases across a period as atomic number increases due to the increased charge of the nucleus.

So, the correct answer is II only, as stated in option 2. The other two options contain at least one incorrect statement, making them false.