An element X (atomic number \[17\] ) reacts with an element Y (atomic number\[20\]) to form a divalent halide.
The element x is:
A. a Metal
B. a Non Metal
C. a Metalloid
D. None of these

Hint: A metal is an element that creates positive ions (cations) readily and it has a metallic bond and Non-metals are the elements which form negative ions by accepting or gaining electrons. Non-metals usually have \[4,{\text{ }}5,{\text{ }}6\] or \[7\] or electrons in their outermost shell.

Complete Step by step answer: The electronic configuration of element 'X' with atomic number \[17\] is \[2,8,7,\] it has \[7\] valence electrons. Ground state electronic configuration is\[1{s^2}2{s^2}2{p^6}3{s^2}3{p^5}\]. Therefore, it lies in the group\[17{\text{ }}\left( {10{\text{ }} + {\text{ }}7} \right)\] . Since in element X, the third shell is being filled, it lies in the third period. X is chlorine.
 It is a Non metal.

The electronic configuration of element 'Y' with atomic number \[20\] is \[2,8,8,2.\]The ground state electron configuration is 20Ca:\[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}\], it has \[2\] valence electrons, It lies in group \[2\] and element Y, fourth shell is being filled, It lies in \[4th\] period, Y is calcium.
Since, element X is (Chlorine) has seven electrons in the valence shell and needs one more electron to complete its octet. Therefore it is non-metal. Element Y has two electrons in the valence shell which it can easily lose to achieve the stable electronic configuration of the nearest inert gas, therefore, it is a metal.
Element X and element Y react to form a divalent halide, i.e ${CaC{l_2}}$ in divalent halide.

Hence the correct option is B.

Note: Nonmetals have high electronegative. This means that the atoms of nonmetals have a strong tendency to attract more electrons and A metalloid is an element that has properties that are intermediate between metals and nonmetals.