Question

An element X has atomic number 19. What will be the formula of its oxide?
A. ${{X}_{2}}O$
B. $XO$
C. $X{{O}_{2}}$
D. ${{X}_{2}}{{O}_{3}}$

Answer 1

Hint: Atoms of elements have specific valency which gives them a tendency to gain or lose electrons into or from their outermost shells respectively full stop atoms after addition or removal of electrons from ions.
The correct answer is (A).

Complete answer:
All the elements which are present in the universe tend to acquire stability. The stability of the elements can be achieved by them by having stable configuration such as half-filled or fulfilled shells. The atoms of these elements lose or gain the electrons to attend is half filled or fully filled stable configuration.
The atoms after loss or gain of electrons acquire some charge (positive charge if the electrons are lost and negative charge if the electrons are gained) and are called as ions. Positively charged ions are portrayed as cations and negatively charged ions are anions.
The loss or gain of electrons makes the elements carrying the opposite charges (cations and anions) susceptible to come in contact with each other and join together chemically. This joining of two elements form compounds. The elements tend to join with the counterpart which can most probably help them to achieve stability and neutralize their charges.
In the above X element, if we write its electronic configuration it would be having one electron in its outermost shell full stop oxygen has 6 electrons in its outermost shell.
The x element can gain stability while using one electron and oxygen can gain stability if it gains two electrons. So, for oxygen to have two electrons 2 X atoms must join with one oxygen and the resulting compound will be ${{X}_{2}}O$.

Note: The elements, after the compound is formed, do not retain their own individual properties. The chemical properties of the compound are different from its constituent elements.