Question

Write the number of periods and groups in the modern periodic table. How does the metallic character of elements vary on moving from (i) left to right across the period and (ii) down a group? Give a reason to justify your answer.

Answer 1

Hint: As we know the horizontal rows on the periodic table are called periods whereas the vertical columns on the periodic table are called groups or families because of having the same chemical properties. We also know that elements can either be metals or non- metal or metalloid. Metallic character refers to the ease with which an atom can lose electrons.

Complete answer step by step:
All the members of a family of elements have the same number of valence electrons and similar chemical properties.
1-When the new principal energy begins filling with electrons then-new periods begin. Only two elements that are Hydrogen and Helium are present in period 1 while eight elements are present in periods two and three whereas periods four and five have a total of eighteen elements. Similarly, periods six and seven have 32 elements.

2-There are a total of eighteen groups present in a modern periodic table.
As the name suggests, metallic character indicates the level of reactivity of metal in which metals tend to lose electrons during the chemical reaction with low ionization energy.

3-Now let us discuss ionization energy in brief: Ionization energy denoted as I E is the minimum amount of energy required to remove most loosely bound electrons the valence electrons of an isolated gaseous atom in its ground state.

4-Now we will see, how the metallic character of elements vary on moving from left to right across the period: As we know along the period, from left to right, the effective nuclear charge increases due to increase in many protons, due to which force of attraction between nucleus and valence electrons increases and ability to lose electrons that is the metallic character decreases when we move from left to right across the period of the periodic table.

Similarly, metallic character increases as we move down a group and this is because atomic size increases down a group, the force of attraction between nucleus and valence electrons decreases and electrons losing tendency increases. Therefore, metallic character increases.

Note: Remember, not to confuse among ionization energy and electron gain enthalpy because ionization energy is the amount of energy required to remove an electron from the outermost shell in the gaseous state whereas electron gain enthalpy is the energy released when an electron added to an isolated gaseous atom.