Q.No 1. What do you mean by periodicity of properties?
Ans. The term periodicity of properties indicates that the elements with similar properties reappear at certain regular intervals of atomic number in the periodic table.
Q.No 2.Why do the elements placed in the same group have similar properties.
Ans. If we examine the valence shell configuration of various elements, we shall find that in any group,similar valence -shell configuration of the elements reoccur after certain intervals of atomic number. This reoccurrence of similar valence-shell configuration of the elements at certain regular intervals of atomic number is the cause of periodicity of properties.
Q.No 3. What is shielding effect?
Ans. In a multi-electron atomic,the valance shell electrons are attracted by the nucleus and also at the same time repelled by the electrons present between the nucleus and the valence shell electrons.The combined effect of these two forces is that the actual force exerted by the nucleus on the valence shell electrons is partially decreased by the presence of repulsive force exerted by the inner-shell electrons. This decrease in the attractive force by the nucleus on the valence-shell electrons is called screening effect or shielding effect.
Q.No 4.Define group trend.
Ans. Group trend is the tendency of the properties of elements in a group to vary in a regular way.
Q.No 5. What is effective nuclear charge?
Ans. It is due to the shielding effect of the inner electrons on the outer electrons that the valence-electrons experience less attractive pull from the nucleus.The decrease in the attractive force reduces the nuclear charge, Z represented by the atomic number of the element.This decrease nuclear charge is called effective nuclear charge.
Q.No 6.Define atomic volume.
Ans. Atomic volume is defined as the volume in cm3 occupied by the one gram atom of the element in the solid state.It is obtained by dividing the atomic weight of element by its density.
Q.No 7. What do you know about atomic radius?
Ans. We know that an atom is composed of a compact nucleus sorrounded by an electron cloud which does not have sharply defined boundary because of its diffused nature.The diffused nature of the electron cloud make it difficult for us to give an exact definition of atomic size or atomic radius. Thus the atomic radius is an arbitrary, concept and is influenced by the nature of neighbouring atoms. However, it is usually considered as the distance from the center of the nucleus to the point where the electron density is effectively zero.
Q.No 8. What are isoelectronic species?
Ans. Iso-electronic species are the atoms or ions which have the same number of electrons and the electronic configuration,but different magnitude of electronic charge. For example C4-, N3-,O2-, F- etc.
Q.No 9. Define bond order.
Ans. Bond order is defined as the number of covalent bonds between the two bonded atoms. The bond length decreases with the increase of multiplicity.
Q.No 10. What is ionization energy?
Ans. It is defined as the amount of energy required to remove the most loosely bound electron from the isolated neutral gaseous atom in its lowest energy state to form unipositive ion.It is also called ionization potential.
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