A covalent bond is defined by the sharing of electron pairs between atoms. A single bond involves the sharing of one pair (two electrons). Consequently, a double covalent bond involves the sharing of two pairs of electrons, totaling four electrons shared between the two bonded atoms to achieve stability.

Electrovalent or ionic compounds consist of ions held together by strong electrostatic forces. In the solid state, these ions are fixed in a lattice and cannot conduct electricity. However, when melted (fused) or dissolved in water, the ions become mobile, allowing the substance to conduct an electric current.

Ionic compounds are generally insoluble in non-polar solvents like alcohol due to their high lattice energy. In the solid state, ions are locked in a rigid crystal lattice and cannot move, making them poor conductors of electricity. They only conduct when molten or dissolved in water, where ions become mobile. Thus, statement 1 is correct, and statement 2 is incorrect.

In a chloropropane molecule (C3H7Cl), there are two C-C single bonds, seven C-H single bonds, and one C-Cl single bond. Summing these (2 + 7 + 1) results in a total of 10 covalent bonds. Note: The source formula C3H2Cl is chemically impossible for a saturated alkane derivative, so the calculation assumes the standard propyl chloride structure.

Element X has a valency of 4 (X4+), and element Y has a valency of 2 (Y2-). To form a neutral compound, the total positive and negative charges must balance. One atom of X (+4) requires two atoms of Y (-2 each, totaling -4) to neutralize the charge. Therefore, the resulting chemical formula is XY2.

Covalent compounds are held together by relatively weak intermolecular forces rather than strong ionic bonds. Consequently, they typically exhibit low melting and boiling points, are poor conductors of electricity, and are generally more soluble in non-polar organic solvents than in water.

Ionic compounds are held together by strong electrostatic forces between oppositely charged ions in a crystal lattice. These strong forces require significant thermal energy to overcome, resulting in high melting and boiling points. They are generally brittle, non-conductive in solid form, and soluble in polar solvents like water, rather than non-polar organic solvents.

An element with an atomic number of 8 is Oxygen, which has an electronic configuration of 2, 6. To achieve a stable octet (8 electrons in the valence shell), it needs to gain two electrons. When reacting with sodium (which loses one electron), oxygen gains two electrons to form an oxide ion (O2-).

As the size of atoms increases, the distance between the nuclei and the shared bonding electrons increases. This greater distance leads to weaker orbital overlap and reduced electrostatic attraction, resulting in a weaker chemical bond compared to smaller atoms.

Ionic compounds are formed through the complete transfer of electrons from a metal to a non-metal, resulting in the formation of positively charged cations and negatively charged anions. These oppositely charged ions are held together in a crystal lattice by strong electrostatic forces of attraction, which are governed by Coulomb's Law.