What is atom?
An atom is the smallest unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across. A human hair is about a million carbon atoms wide.
Atoms are composed of a central nucleus that is surrounded by a cloud of electrons. The nucleus is made up of protons and neutrons, which are particles that are much heavier than electrons. The number of protons in the nucleus determines the atomic number of the atom, which is what identifies the element. The number of neutrons in the nucleus determines the isotope of the atom.
Electrons are held in place around the nucleus by the electrostatic attraction between the negatively charged electrons and the positively charged protons. Electrons can only exist in certain energy levels or orbitals. When an electron absorbs energy, it can jump to a higher energy level. When an electron loses energy, it can jump to a lower energy level. This movement of electrons is responsible for the emission of light.
Atoms can combine with other atoms to form molecules. Molecules are held together by chemical bonds, which are the forces that attract atoms to each other. There are three main types of chemical bonds: ionic bonds, covalent bonds, and metallic bonds.
Ionic bonds are formed between atoms that have different electronegativities. Electronegativity is a measure of an atom's ability to attract electrons. When an atom with a high electronegativity attracts electrons from an atom with a low electronegativity, the two atoms become oppositely charged and are attracted to each other.
Covalent bonds are formed between atoms that share electrons. When two atoms share electrons, they create a strong attraction between each other.
Metallic bonds are formed between atoms that are arranged in a regular lattice structure. The electrons in a metallic bond are free to move throughout the lattice, which allows the metal to conduct electricity and heat.
Atoms are the building blocks of all matter. They are incredibly small, but they are the basis for all of the chemistry that we see around us
