Define ' element ' according ot boyle .

Who classified elements according the their atomic numbers ?

Define element and compound. Give examples.

Electronegativity of an element is the average of its ionisation energy and electron affinity according to

Assertion: According to Mendeleeff, periodic properties of elements is a function of their atomic masses. Reason : Atomic number is equal to number of protons

Different elements exist in different physical states. However only gaseous state is taken into consideration for all elements for defining IP (or) EA. Give reason.

Assertion (A) : It is a better way of arranging the elements in the periodic table is according to the increasing atomic number. Reason (R) : This arrangement. according to increasing atomic number eliminated the problem of anomalous series.

Define transition elements. Name the different transition series.

Guess the atomic weight of middle element if the atomic weights of first and last elements are 7 and 39 respectively according to Law to triaids.