Question

What is a periodic property? How the following properties vary in a group and in

period?

(a) Atomic radius (b) Electron gain enthalpy​

Answer 1

Explanation:

The periodic table arranges the elements by periodic properties, which are recurring trends in physical and chemical characteristics. ... These trends explain the periodicity observed in the elemental properties of atomic radius, ionization energy, electron affinity, and electronegativity.

a)The atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons.

b)Electron gain enthalpy is the energy required to add an electron in a neutral atom. Because, in most of the cases atom releases energy, the electron gain enthalpies are negative. As we move from left to right in the periodic table the electron gain enthalpy (its negative value), in the same period, increases.

Answer 2

The electronic configuration of the valence shell of any two elements in a given period is not the same. This is called periodic property.

Explanation:

• The physical and chemical properties of elements are related to their electronic configuration particularly the outer shell configurations.

    A) Atomic radius:

• Atomic radius is determined as the distance between the nuclei of two identical atoms bonded together.
• The atomic radius of atoms generally decreases from left to right across a period.
• The atomic radius of atoms generally increases from top to bottom within a group.

    B) Electron gain enthalpy:

• The enthalpy change accompanying the addition of an electron to a neutral gaseous atom is called electron gain enthalpy.
• Electron gain enthalpy becomes more negative along the period.
• Electron gain enthalpy becomes less negative down the group.