Question

please help me to find this questions answers

Answer 1

a. horizontal rows are called periods.

there are 7 periods in modern periodic table

b. pd.1 is the shortest

elements:Hydrogen Helium

c. pd. 2 n 3 are short periods

elements of pd.2:Lithium

elements of pd.3:Sodium

d. pd.4 n 5 are long
no. of elements is 18


e.pd. 6 n 7 are very long
no. of elements is 32
pd. 7 is incomplete so pd. 6 is complete