Ionic Bonding

electron density maps show closed contours around each ion with a gap between them indicating discrete ions; molten NaCl conducts electricity showing the presence of mobile charged particles

Cu²⁺ ions migrate towards the cathode (negative electrode); CrO₄²⁻ ions migrate towards the anode (positive electrode); this shows the species carry opposite charges and exist as separate ions

the magnesium atom loses two electrons from its outer shell; forming a Mg²⁺ ion with the electronic configuration of neon

O + 2e⁻ → O²⁻

the brackets indicate the species is a discrete ion; the charge shows the net number of electrons lost or gained

to track the origin of each electron and show clearly that electron transfer has occurred between atoms

a regular repeating three-dimensional arrangement of positive and negative ions; held together by electrostatic attractions extending throughout the structure

each Na⁺ is surrounded by six Cl⁻ ions and each Cl⁻ is surrounded by six Na⁺ ions

the strong electrostatic attraction; between oppositely charged ions

the electrostatic attraction acts equally in all directions around each ion; so each ion attracts oppositely charged ions in every direction within the lattice

Mg²⁺ and O²⁻ carry higher charges than Na⁺ and Cl⁻; Mg²⁺ and O²⁻ have smaller ionic radii than Na⁺ and Cl⁻; both factors increase the electrostatic attraction so more energy is required to break the lattice

NaF has stronger ionic bonding; F⁻ has a smaller ionic radius than Cl⁻ so the ions are closer together and the electrostatic attraction is stronger

each successive ion has one more occupied electron shell; so the outer electrons are further from the nucleus

both ions have ten electrons (isoelectronic); Al³⁺ has 13 protons while N³⁻ has only 7 protons; the greater nuclear charge in Al³⁺ pulls the electron cloud in more tightly, reducing the radius

O²⁻ > F⁻ > Na⁺ > Mg²⁺; all four ions are isoelectronic with ten electrons; nuclear charge increases from O (8 protons) to Mg (12 protons), so the attraction on the electron cloud strengthens and the radius decreases

the distortion of the electron cloud of an anion; caused by the attractive pull of a nearby cation

Mg²⁺ has the greater polarising power; Mg²⁺ has a higher charge and a much smaller ionic radius than Cs⁺; both factors increase the electrostatic pull on the electron cloud of a neighbouring anion

I⁻ has a much larger ionic radius than F⁻; the outer electrons in I⁻ are further from the nucleus and held less tightly, so the electron cloud is more easily distorted

Mg²⁺ and O²⁻ carry larger charges than Na⁺ and Cl⁻; Mg²⁺ and O²⁻ also have smaller ionic radii than Na⁺ and Cl⁻; both factors increase the strength of the electrostatic attraction in the lattice, so more energy is needed to overcome it and the melting point is higher; in AlCl₃, the small highly-charged Al³⁺ cation has high polarising power; Al³⁺ distorts the electron cloud of the larger Cl⁻ anion, concentrating electron density between the ions; this introduces significant covalent character; in NaCl, Na⁺ has only +1 charge and a larger radius, so its polarising power is weak and the bonding remains essentially ionic