Study Portal 8 – Chapter 8

Chemical Reactivity


Q1.      What do you mean by chemical reactivity?

Ans.    The reactivity of a substance is due to the tendency of donating or accepting or sharing the electrons, determined by the electropositive or electronegative characters.

The chemical reactions on the basis of their speed are divided into three categories.

  • Slow reaction:- rusting of iron
  • Moderate reaction:- the reactions of organic
  • Very fast: – the reaction between ionic compounds.

Q2.      Define metallic elements.

Ans.    Metals are the elements which are electropositive and form cations by losing their valance shell easily. Elements of group I to group 13 are all metals except hydrogen and boron, bottom elements of group 14 to 16 are also metals. Metals are good at conducting electricity and heat. They can be transformed in any desire shape. The metals are shiny. The metals are electropositive in nature. Hence the reactivity of the metals is also increases down the group and decreases along the periods.

Q3.   Compare reactivity between alkali metals and alkaline earth metals.

The alkali metals are the group-I, and the alkaline earth metals are the group-II of the periodic table. The alkaline metals are soft, very reactive having a high value of electropositivity. They do not occur in Free State. The alkali metals react vigorously with water to form the product hydroxides while the alkaline earth metals react comparatively slowly.

Q4.      What are noble metals?

Ans.    The noble metals are the metals that are resistant to corrosion and oxidation in moist air. They are usually precious and rare in the earth’s crust palladium, silver, osmium, and iridium, platinum and gold are the common examples of the noble metals. Most of the noble metals are used in the jewelry making. The noble metals tend to be inert toward the common reagents. The important reason for the inertness of the noble metals is their electronic arrangement.

Q5.   Define non-metals, their occurrence and characteristic of electronegative.

Ans.    There is no rigorous definition for the term non-metal, it covers general spectrum of behavior the common properties considered characteristic of a non-metal include.

  • Poor conductors of heat and electricity when compared to metals.
  • They form acidic oxides.
  • In solid form, they are dull and brittle.
  • Usually have lower densities than metals.
  • They have significantly lower melting and boiling points than metals.
  • They have high electronegativity.


Top elements of group 15, 16 and 17 are non-metals. i.e. only seventeen elements in the periodic table are generally considered non-metals. Non-metals make up most of the crust atmosphere and oceans of the earth.

Electronegative character

The element having high electron affinity or high electronegativity have high tendency to gain electrons and form negative ion. The electronegative character increases along the period and decreases down the group.

Q6.   What are halogens? Describe comparison of reactivity of halogens.

Ans.    Elements of group 17 i.e. F2, Cl2, Br2, and I2 are called halogens.

  • Fluorine is a yellow gas.
  • Chlorine is a greenish yellow gas.
  • Bromine is a reddish brown liquid.
  • Iodine is a deep violet solid.

Comparison of the reactivity of halogens

As we know, the chemical reactivity of halogens decreases down the group i.e. from top to bottom therefore fluorine is the most reactive as compared to Cl2, Br2 and I2. Halogens are slightly soluble in water, their solubilities decreases from top to bottom in a group. F2 can not be dissolved in water because it decomposes water.

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