Forces of Attraction
The forces of attraction are literally the powers that keep the world together. The atoms attracted to each other become molecules, while aggregated molecules form our bodies and most things around us. The investigation of the forces of attraction explains how material substances keep their shapes without falling to pieces.
The forces of attraction on the micro-level influence atoms, molecules, and appositively charged ions. They arise when the electrons of one particle come into the electric field of another particle’s nucleus. Intramolecular forces of attraction exist between atoms within a molecule or ions within a lattice, while intermolecular forces hold molecules together.
Intramolecular forces can form three kinds of bonds – ionic (electrovalent), covalent, and metallic – these determine the properties of a resulting substance. Ionic bonds arise between atoms with large differences in electronegativity. The materials formed by aggregated ions are hard, rigid, and brittle. They have high melting and boiling points, conduct electricity in their molten state, and dissolve in water. Covalent bonds appear between atoms with similar electronegativity, when their atomic orbitals overlap and electrons become shared between their nuclei. Covalent compounds exist as gases or liquids at room temperature. They boil at relatively low points, do not conduct electricity, and can only be dissolved in non-polar solvents. Metallic bonds are formed by powerful attractions between positive ions and delocalized electrons. Metals are the hardest and strongest substances, and are the best electricity conductors. The differences between these three kinds of compounds result not only from the different nature of fundamental particles (ions or atoms), but also from the peculiarities of their interactions.
Intermolecular forces are subdivided into the forces of attraction and repulsion. For example, two molecules of water will be driven together by a force of attraction, while each of them will be repulsed from a molecule of grease. Intermolecular forces of attraction are generally much weaker than those between atoms and ions, so molecular compounds are usually softer than metals with their atomic lattice. Intermolecular attractions can exist between molecules in the same substance, between molecules of different substances (e. g. when two liquids mix), between atoms of noble gases (helium, radon), and between molecules of one substance and ions of another.
The various types of forces of attraction create ionic, covalent, metallic, and molecular structures; all with their own distinctive features. The understanding of these forces is crucial in both understanding the properties of substances and creating new materials with pre-determined features.