Question

An element X(Atomic number 12) reacts with another element Y(atomic number 17) to form a compound Z. Which of the following statements are true regarding this compound?
I. Molecular formula of Z is ${\text{X}}{{\text{Y}}_{\text{2}}}$.
II. It is soluble in water.
III. X and Y are joined by the sharing of electrons.
IV. It would conduct electricity in the molten state
A) (II) and (III)
B) (I) and (III)
C) (I),(III) and (IV)
D) (I),(II) and (IV)

Answer 1

The oxidation number is also called oxidation state; it is defined as the numbers of the electrons shared, lost, or gained by an atom when it is forming a chemical bond with different atoms. The oxidation state of the alkaline earth metals is always taken as +2 and the Oxidation state of the halogen is -1.

Complete step-by-step answer:
Here, an atomic number of the X is 12 indicates it is magnesium represented by the atomic symbol Mg while element Y has an atomic number 17 hence it is chlorine. When these X and Y combine leads to form compound Z with formula ${\text{X}}{{\text{Y}}_{\text{2}}}$. As magnesium is alkaline earth metal loses two electrons and attains the stable configuration of the neon and carries +2 charge. Chlorine is a halogen it accepts one electron and attains a stable configuration of the argon and carries -1 charge.

To balance the charge on the magnesium two chlorine atoms are required.
${\text{M}}{{\text{g}}^{2 + }}\, + {\text{C}}{{\text{l}}^ - } \to {\text{MgC}}{{\text{l}}_{\text{2}}}$
Thus, the compound formed Z has molecular formula is ${\text{MgC}}{{\text{l}}_{\text{2}}}$ that is ${\text{X}}{{\text{Y}}_{\text{2}}}$. Therefore, the statement (I) is correct.
Here, the compound formed ${\text{MgC}}{{\text{l}}_{\text{2}}}$ is ionic and polar therefore it is dissolved in water. Therefore, statement(II) is correct.
Here, the formation of the ${\text{MgC}}{{\text{l}}_{\text{2}}}$ is takes place by the electron donation and electron gain by the elements. Here, magnesium metal gives its two-valence electron to two chlorine atoms and there is the formation of the ionic bond which is not formed by the sharing of electrons. Therefore, statement(III) is incorrect.

As ${\text{MgC}}{{\text{l}}_{\text{2}}}$in the molten state that is dissolved in water the solution formed contains the magnesium and chloride ions which are responsible to conduct the electricity. Therefore, statement(IV) is correct.
Now, option(D) I, II, and IV is correct because all statement I, II, III are correct.

Note: Substance or compound which dissolved in water and form ions. These freely moving ions conduct the electricity hence, such a substance or compound is the conductor. Ionic solids are dissolved in water and dissociated in respective ions hence, their molten solution acts as conductors.