The periodic table is a systematic arrangement of elements based on their atomic number and electron configuration. It is used to organize and understand the properties and trends of elements.

Periodic properties are properties of elements that change in a predictable way as you move across or down the periodic table. These properties help in understanding the behavior and characteristics of elements.

Option 1: Atomic size is a periodic property. Atomic size generally decreases from left to right across a period and increases from top to bottom in a group.

Option 2: Valency is a periodic property. Valency refers to the number of electrons an atom can gain, lose, or share in a chemical reaction. It depends on the number of valence electrons an atom has, which varies across the periodic table.

Option 3: Radioactivity is not a periodic property. It does not show any trend or pattern as you move across or down the periodic table. The radioactivity of an element depends on the specific isotopes of that element, which can vary independently of the element`s position in the periodic table.

Option 4: Electronegativity is a periodic property. Electronegativity indicates the ability of an atom to attract electrons in a chemical bond. It generally increases from left to right across a period and