Middle School Physical Science: Chemical Bonding - Introduction to Chemical Bonds — Flashcards

Elements form compounds when they combine chemically. This is called chemical bonding. Atoms of different elements join together to form molecules, crystals, or other structures. The atoms are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions. It occurs when they share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom.   

Consider water as an example. A water molecule consists of two atoms of hydrogen and one atom of oxygen. A hydrogen atom has just one electron, and an oxygen atom has six valence electrons. In a water molecule, each hydrogen atom shares a pair of valence electrons with the oxygen atom. One electron in the pair comes from hydrogen and one comes from oxygen. By sharing electrons, each atom has electrons available to fill its sole or outer energy level. This gives it a more stable arrangement of electrons that takes less energy to maintain.