Periodic table trends based on the properties of elements

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05 Periodic table

  • The physical and chemical properties of elements show a regular variation in the oeriods and groups of the periodic table.
  • The properties of an element are a periodic function of their atomic number according to the modern periodic table, are related to the electronic configuration of the elements.
  • There is a common trend in properties as one moves across a period from left to right or down the group.
  • This trend in properties is known as periodic properties, the most significant among which are atomic size, metallic character, non-metallic character, ionization potential, electron affinity, and electronegativity.

VALENCY:

  • On moving from left to right in each short period, the valency of elements increases from 1 to 4 and then decreases to zero.
  • Elements in the same period have different valencies.
  • Valency of an element is determined by the number of valence electrons present in the atom of the element.
  • The number of electrons lost or gained by one atom of an element to achieve the nearest inert gas configuration, gives the valency of the element.

ATOMIC SIZE TRENDS:

  • Atomic radius is the distance between the center of the nucleus and the outermost shell of an atom.
  • The atomic size increases in a group due to the addition of shells as one move from one period to another.
  • The atomic size decreases across a period as the number of shells remain the same but nuclear charge increases.
  • So, electrons are pulled from the outermost shell towards the nucleus and their size reduces.

METALLIC CHARACTER TRENDS:

  • Metals are the elements which lose electrons to form cations.
  • Metallic character increases as we move down the group.
  • This is because the atomic size increases so that electrons are lost easily.
  • The atomic size decreases across a period as we move from left to right because there is an increase in nuclear charge.
  • So it is difficult for an atom to lose electrons.

NON-METALLIC CHARACTER TRENDS:

  • Non-metals are the elements which have a tendency to gain electrons.
  • The non-metallic character increases as one move across a period.
  • This is due to an increase in the nuclear charge and decrease in the atomic size.
  • But as we move down the group the non-metallic character decreases due to increase in the atomic size.

CHEMICAL REACTIVITY:

  • On moving from left to right in a period, the chemical reactivity of elements first decreases and then increases.
  • All the elements of a group show similar chemical properties.
  • The chemical reactivity of metals increases on going down in a group of the periodic table.
  • The chemical reactivity of non-metals decreases on going down in a group of the periodic table.

NATURE OF OXIDES:

  • On moving from left to right in a period, the basic nature of oxides decreases and the acidic nature of oxides increases.
  • Ongoing down in a group of the periodic table, there is no change in the nature of oxides of element.

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