Ions and Isotopes

• Molecules are neutral particles composed of two or more atoms held together by chemical bonds
• A molecule can be made up of similar or different types of atoms
• Example: A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom, giving it the chemical formula H2O
• Each chemical element has a different atomic number, which is the number of protons in an atom's nucleus
• Mass number (atomic mass number) is the number of protons plus the number of neutrons in an atom's nucleus
• Chemical symbols represent elements on the periodic table, with each element having its own unique symbol made up of one or two letters
• The first letter of a chemical symbol is always capitalized, and if there is a second letter, it is written in lowercase
• Niels Bohr expanded on Rutherford's atomic theory, proposing that electrons have specific energy levels and travel in certain orbits based on that energy
• Bohr's model is used to illustrate electron energy levels and how outer orbits determine an atom's chemical properties
• Ion: an atom or molecule that has lost or gained one or more of its outer valence electrons, resulting in a positive or negative electric charge
• Anions are negatively charged ions, while cations are positively charged ions
• Ionization happens when electrons are gained or lost, but the number of protons and neutrons remains the same
• Isotopes are atoms of the same element with different numbers of neutrons, leading to variations in mass number
• Example: Isotopes of hydrogen include protium (no neutrons), deuterium (one neutron), and tritium (two neutrons)
• Hydrogen is the lightest and most abundant element in the universe, making up more than 90% of all atoms
• Hydrogen has three common isotopes: protium, deuterium, and tritium, with different numbers of neutrons
• Hydrogen is a fuel for stars like the sun through fusion reactions, releasing vast amounts of energy