defination of periodic properties
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Answer:
Periodic property : The physical and chemical properties of elements are related to their electronic configuration particularly the outershell configurations. The electronic configuration of valence shell of any two elements in a given period is not same. Due to this reason elements along a period possess different chemical properties with regular gradation in their physical properties from left to right. This is called periodic property.
a) Atomic radius: The distance between the nucleus and outermost orbitals called as atomic radius.
Group : Atomic radii increases from top to bottom in a group, the atomic number of the element increases.
Period : Atomic radii of elements decrease across period from left to right. As electrons enter into the same main shell.
b) Ionisation energy: The energy required to remove electron from the outer¬most orbit or shell of a neutral gaseous atom is called ionization energy. Group : Ionization energy decreases as we go down in a group.
Period : IE increases from left to right in a period.
c) Electron affinity : Electron affinity of an element is defined as the energy liberated when an electron is added to its neutral gaseous atom.
Group : Electron affinity decreases as we go down in a group.
Period : Electron affinity increase along a period from left to right.
d) Electronegativity : The electronegativity of an element is defined as the relative tendency of its atom to attract electrons towards it when it is bounded to the atom of another element.
Group : Electronegativity values of elements decreases as we go down in a group.
Period : Electronegativity increases along a period from left to right.
Ionization energy increases from left to right in a period. Ionization energy decreases from top to bottom in a group.
a) Na, Al, Cl: All these three elements are in the same period atomic sizes are in the order of Na > Al > Cl. Ionization energy is in the order of Cl > Al > Na.
b) Li, Be, B : All these three elements belong to same period.
Electronic configuration of Li: 1${{s}^{2}}$2${{s}^{1}}$
Be :1${{s}^{2}}$2${{s}^{2}}$
B : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{1}}$
.-. Ionization energy is in the order of Be > B > Li
c) C, N, O : All these three elements belong to same period.
Electronic configuration of C : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{2}}$
N : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{3}}$ (half filled)
O : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{4}}$
.-. Ionization energy is in the order of C > N > O
d) F, Ne, Na :
Electronic configuration of F : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{5}}$
Ne : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{6}}$ (Inert gas)
Na : 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{6}}$3${{s}^{1}}$
.-. Ionization energy is in the order of Ne >F > Na
e) Be, Mg, Ca : All these elements belong to same group. Atomic size of these elements are in the order of Ca > Mg > Be.
Answer:
The properties which repeate themselves at regular intervals are called periodic properties