Question

List all the exceptions that occurs in the modern periodic table..

Answer 1

1) position of argon is before potassium although mass no of potassium is less than argon
2) hydrogen is placed in period 1 group 1 although it is gaseous & diatomic, can form anion & covalent compounds
3) rare earth elements and actinides - each of 14 elements are placed in the same group