Question

What is the periodic property? How will the following properties in options increases in left to right in:
A. Electron gain enthalpy
B. Ionization Enthalpy $\left( {I.E.} \right)$
C. Electronegativity $\left( {E.N.} \right)$
D. Atomic radius

Answer 1

Hint: All the chemical elements which exist on the earth are present in the modern periodic table . The vertical rows are termed as groups , there are a total 18 groups and the horizontal rows are termed as periods , there are a total of seven periods .

Complete step by step answer: The physical and chemical properties of an element or a periodic function of their atomic number these properties are termed as periodic properties.
-Electron gain enthalpy: The amount of energy released when an isolated neutral gaseous atom adds up an electron to form an anion is known as the electron gain enthalpy .
 When we move across a period in the periodic table from left to right the electron gain enthalpy becomes more negative due to the decrease in atomic size and increase in nuclear charge .
-Ionization Enthalpy: The amount of energy required to remove the most loosely bound electron from a neutral gaseous atom is known as the ionisation enthalpy.
When we move in a Periodic table from left to right the ionisation enthalpy increases because the atomic size decreases.
-Electronegativity: The tendency of an atom to attract or pull the shared pair of electrons of a covalent bond towards itself is known as the electronegativity.
 When we move from left to right in a period the electronegativity increases as the size of the atom decreases.
-Atomic Radius: The distance from the centre of the nucleus to the outermost shell or to the point where the nucleus exerts influence is known as the atomic radius .
When we move from left to right across a period the atomic size decreases because the electrostatic forces of attraction increase .
Thus , the electron gains enthalpy , ionization enthalpy and electronegativity increases as we move from left to right in a period.
Hence option A , B and C are correct.

Note: This principle was first discovered by Russian chemist DMitri Mendeleev in $1871$ after a number of investigations by scientists in the ${19^{th}}$ century. After that Mendeleev also proposed a periodic system of elements which were based not only on the chemical and physical properties of the elements and their compounds.