Matter around us is found in the form of elements, compounds and mixtures

Matter around us is found in the form of elements, compounds and mixtures. The elements contain atoms of only one type. Around the year 1800, only 30 elements showing different properties were known.

Scientists of that age discovered a pattern in their properties and based on that pattern, several attempts were made to classify elements. The earliest attempt was to classify the elements as metals and non-metals. The latest is the ‘Modern Periodic Table’. This table consists of 7 periods and 18 groups. Each element of a group in the periodic table has the identical outer shell electronic configuration. In other words, the groups in the periodic table signify an identical outer shell electronic configuration. As we go down the group in the periodic table, the number of shells increases. 

 a. Write the need to classify elements.

 b. How many groups are there in the ‘Modern Periodic Table’ ?

 c. Which one of the following statements is not correct about the ‘Modern Periodic Table’ ? 

1. It is based on atomic masses.
2. The position of isotopes is not disputed.
3. The position of isotopes is easily assigned.
4. It separates metals from non-metals. 

 d. The cause of periodicity of properties of elements is 

1. Increasing atomic radius
2. Increasing atomic mass
3. Increasing nuclear charge
4. The recurrence of similar outer electronic configuration

Answer

1.  to make the study of the elements easier
2. 18 groups
3. (A) - It is based on atomic masses
4. (D) - The recurrence of similar outer electronic configuration