Which of the following properties decrease down a column in the periodic table?
-effective nuclear charge
-ionization energy
-atomic radii
-ionic radii

Effective nuclear charge and ionization energy decreased down in the column.

Explanation:

Along Group:

As we move from top to bottom in group the atomic size increases with increase of atomic number. The electron is added into the next shell hence the valance electrons farther away from the nucleus and hold of nucleus become weaker on the valance electrons. The addition of electrons also increase the shielding and protect the outer electrons from the hold of nucleus. Thus it becomes easier to remove the electron from an atom and less energy is required that's why ionization energy decreases from top to bottom and effective nuclear charge also decrease because of shielding effect.

Along period:

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 and shielding remain constant due to addition of electron in same shell. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases and ionization energy increases.

i think its 100.

hope this !