Welcome to high school chemistry! Chemistry is the study of matter and its properties. Matter is anything that has mass and takes up space. It exists in three main states: solid, liquid, and gas. In solids, particles are tightly packed and vibrate in fixed positions. In liquids, particles are close but can move around each other. In gases, particles are far apart and move freely.
Now let's explore atomic structure. Atoms are the basic building blocks of all matter. Every atom consists of three types of particles. The nucleus at the center contains protons, which have a positive charge, and neutrons, which have no charge. Electrons, which have a negative charge, orbit around the nucleus in energy levels or shells.
The periodic table is one of chemistry's most important tools. It organizes all known elements by their atomic number, which is the number of protons in the nucleus. Elements are arranged in groups, which are vertical columns, and periods, which are horizontal rows. Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
Chemical bonding explains how atoms combine to form compounds. There are three main types of bonds. Ionic bonds form when electrons transfer from one atom to another, creating charged ions that attract each other. Covalent bonds occur when atoms share electrons to achieve stability. Metallic bonds involve a sea of delocalized electrons that hold metal atoms together.
Chemical reactions are processes where substances transform into new substances by breaking and forming chemical bonds. In reactions, reactants are converted into products. The law of conservation of mass states that matter cannot be created or destroyed, so chemical equations must be balanced. Reactions also involve energy changes - they can either release energy or absorb energy from the surroundings.