Pressure can have a significant impact on the melting point of ionic compounds, although the effect varies depending on the specific compound and its structure. Generally, increasing pressure tends to increase the melting point of ionic compounds. This is because applying pressure reduces the volume of the compound, making the ions more closely packed. The closer proximity of ions enhances the electrostatic attractions between them, thereby requiring more energy (in the form of heat) to overcome these attractions and melt the compound. However, the extent of the effect of pressure on melting point is influenced by the compound's compressibility and the nature of its lattice structure. Some ionic compounds with more compressible structures may show a more pronounced increase in melting point with increased pressure. It's also worth noting that extreme pressures can lead to phase transitions in some ionic compounds, where the compound changes to a different crystalline structure with different properties.

Ionic compounds can exhibit magnetic properties, but this is less common and depends on the specific ions they contain. The magnetic properties in ionic compounds arise primarily from the presence of transition metal ions or rare earth metal ions. These ions have unpaired electrons in their d or f orbitals, which contribute to magnetic moments. For instance, compounds containing iron(II) or iron(III) ions can exhibit magnetic properties due to the unpaired electrons in these ions. The magnetic behavior of an ionic compound also depends on the arrangement of these magnetic ions within the lattice. In some cases, the magnetic moments of adjacent ions can align in the same direction (ferromagnetism), in opposite directions (antiferromagnetism), or in a more complex manner (ferrimagnetism). The temperature can also influence the magnetic properties of ionic compounds. For example, above a certain temperature known as the Curie temperature, ferromagnetic materials lose their permanent magnetic properties and behave as paramagnets.

The color of ionic compounds is primarily influenced by the presence of transition metal ions. These ions have partially filled d-orbitals, which allow for the absorption of certain wavelengths of light, resulting in the compound exhibiting color. The specific color observed depends on the electronic transitions that occur between different energy levels within the d-orbitals. These transitions are influenced by the crystal field - the arrangement of ions around the transition metal ion. The strength of the crystal field, determined by the nature of the surrounding ions and their distance from the transition metal ion, alters the energy gap between d-orbital levels. For example, copper(II) sulfate (CuSO₄) appears blue due to the specific electronic transitions in the copper ion. Additionally, the oxidation state of the transition metal ion also plays a role in determining the color of the compound. Changes in the oxidation state can alter the electronic structure of the ion, leading to different absorption spectra and hence different colors.

Ionic compounds generally exhibit higher densities than covalent compounds due to the close packing of ions in their lattice structures. In ionic compounds, ions are densely packed in a regular, repeating pattern, minimizing empty space and maximizing the number of ions per unit volume. This dense arrangement is a result of the strong electrostatic forces of attraction between oppositely charged ions. For instance, in sodium chloride, each sodium ion is surrounded by six chloride ions in a cubic arrangement, leading to a high packing efficiency. In contrast, covalent compounds are composed of molecules that are not as tightly packed and often have lower mass per unit volume. The intermolecular forces in covalent compounds are generally weaker than the ionic bonds in ionic compounds, resulting in less dense structures. Furthermore, covalent compounds may have large molecules with complex structures that occupy more space, contributing to their lower density compared to the compact ionic structures.

The size of ions significantly influences the structure and properties of ionic compounds. Larger ions tend to form structures where each ion has a larger coordination number, meaning that it is surrounded by more oppositely charged ions. This is due to the larger ion's ability to accommodate more ions around it. For example, cesium chloride (CsCl) has a body-centred cubic structure due to the large size of Cs⁺ ions. Smaller ions, conversely, form structures with fewer coordination numbers. The size of ions also affects the melting and boiling points of ionic compounds. Larger ions have lower charge density, which leads to weaker electrostatic forces between ions. Consequently, compounds with larger ions generally have lower melting and boiling points compared to those with smaller ions. Additionally, the size of ions can influence the solubility of ionic compounds in water; smaller ions usually form more soluble compounds due to stronger hydration, which helps overcome the lattice energy more effectively.