Question

Define
a)period b) group c)modern periodic law d)Mendeleevs periodic low​

Answer 1

Answer:

Explanation:

1.the seven horizontal rows is knowns as periods

2.the eighteen vertical columns is known as groups

3.the periodic law is changed from atomic weight concept to atomic number concept is called he modern periodic law

4.the law states that  the physical and chemical properties of the element and periodic functions of their atomic weights is called mendeleevs periodic law