The mass number of two atoms X and Y is the same (40 each) but their atomic numbers are different (being 20 and 18 respectively). X and Y are examples of:

Define valency of an element. What valency will be shown by an element having atomic number 14?

What is the relation between the valency of an element and the number of valence electrons in its atoms? Explain with examples.

Which of the following statement is correct about the atom of and element?

There are two species represented as ³⁵Cl and ³⁷Cl. Which of the following statement is correct regarding these species?