What is a periodic property?

CBSE Class 10 CBSE Class 10 Science
,
1
  1. What is a periodic property ? How do the following properties change in a
    group and period ? Explain.
    a) Atomic radius b) Ionization energy c) Electron affinity d) Electronegativity.
  2. Explain the Ionization energy order in the following sets of elements :

a) Na, Al, Cl, b) Li, Be, B c) C, N, O d) F, Ne, Na e) Be, Mg, Ca.

2
  1. 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.
  2. 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.