 # An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound

An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound. Answer the following questions giving reason:
(i) Write the position of P and Q in the modem periodic tables and the molecular formula of the compound formed when P reacts with Q.

Write the names given to the vertical columns and horizontal rows in the modern periodic table. How does the metallic character of elements vary on moving down a vertical column? How does the size of atomic radius vary on moving left to right in a horizontal row ? Give reason in support of your answer in the above two cases.

Configuration is: P (20): 2, 8, 8, 2.
(i) Position of P in modern periodic table:

1. Period = No. of shells = 4
2. Group = Valence electrons = 2.

(ii) Configuration of Q is Q (17) : 2, 8, 7

1. Period = No. of shells = 3
2. Group = Valence electrons = 10 + 7 = 17.

(iii) Formula of the compound is PQ2.