i] An element X has both K and L shells completely filled with electrons. The element has atomic number 10. Identify the element X.
ii] In which group of the periodic table this element is placed? iii) Write its electronic configuration. What is its valency?.

Explanation

i] the element X is Neon (Ne) 
ii] It is placed in the group 18 of the modern periodic table iii] Electronic configuration of Neon is `{:(K,L),(2,8):}` Its valency is 0.