Ionic Bonds - Structure and Properties

Sodium (Na) is in Group 1, so it has 1 electron in its outer shell. Chlorine (Cl) is in Group 17, so it has 7 electrons in its outer shell.

Metals lose electrons to achieve a full outer shell; non-metals gain electrons. Na needs to lose 1 electron (leaving a full shell of 8), and Cl needs to gain 1 electron (completing its outer shell to 8).

When Na loses 1 electron, it has more protons than electrons, giving it a charge of 1+ → Na⁺. When Cl gains 1 electron, it has more electrons than protons, giving it a charge of 1− → Cl⁻.

The correct description is: Sodium loses 1 electron to become Na⁺ and chlorine gains 1 electron to become Cl⁻.

The question asks which option correctly describes the direction of electron transfer and the resulting ion charges when NaCl forms.

Sodium gains 1 electron to become Na⁻ is incorrect. Sodium is a metal in Group 1 — metals lose electrons, they do not gain them. This option has the direction of transfer backwards.

Sharing electrons describes covalent bonding, not ionic bonding. Ionic bonding involves a complete transfer of electrons from metal to non-metal, not sharing.

Sodium loses 7 electrons is incorrect. Na only has 1 electron in its outer shell; it is energetically favourable to lose just 1, not 7. Losing 7 would be extremely unfavourable.

The remaining option — Sodium loses 1 electron to become Na⁺ and chlorine gains 1 electron to become Cl⁻ — correctly describes the transfer and resulting charges.

For a substance to conduct electricity, it must contain charged particles that are free to move. Simply having charges is not enough — the ions must be mobile.

In the solid state, K⁺ and Br⁻ ions are locked in fixed positions within the giant ionic lattice. They can vibrate but cannot travel through the substance, so no conduction occurs.

When melted or dissolved in water, the lattice breaks down and ions become free to move. Free-moving charged ions can carry an electric current, so both states conduct electricity.

The correct result is: Solid: does not conduct; Molten: conducts; Dissolved: conducts.

The question tests whether ions can move freely in each physical state of an ionic compound, which determines electrical conductivity.

Any option where solid conducts is incorrect. In a solid ionic lattice, ions are fixed in position and cannot move to carry charge, so solid KBr does not conduct electricity.

Any option where molten does not conduct is incorrect. When an ionic compound melts, the lattice structure breaks down and ions become free to move, enabling conduction.

Any option where dissolved does not conduct is incorrect. Dissolving KBr in water releases free K⁺ and Br⁻ ions, which can carry charge through the solution.

Only Solid: does not conduct; Molten: conducts; Dissolved: conducts is consistent with all three principles.