Atoms, Isotopes, Ions, and Molecules: The Building Blocks
The Structure of the Atom
Atoms are made up of protons, neutrons, and electrons, which are responsible for their mass and charge.
Atomic Number and Mass
The atomic number is the number of protons in an element while the number of protons plus the number of neutrons determines the mass number.
Isotopes are different forms of an element that have the same number of protons, but a different number of neutrons.
The Periodic Table
The periodic table is a means of organizing the various elements according to similar physical and chemical properties.
Electron Shells and the Bohr Model
Niels Bohr proposed an early model of the atom as a central nucleus containing protons and neutrons being orbited by electrons in shells.
Electron orbitals are three-dimensional representations of the space in which an electron is likely to be found.
Chemical Reactions and Molecules
Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart.
Ions and Ionic Bonds
Ionic bonds are attractions between oppositely charged atoms or groups of atoms where electrons are donated and accepted.
Covalent Bonds and Other Bonds and Interactions
Covalent bonds result from a sharing of electrons between two atoms and hold most biomolecules together.