Basic Chemistry

• Matter refers to anything that takes up space and has mass.
• element is a substance that cannot be broken down into substances with different properties; composed of one type of atom.
• Both the Earth’s crust and all organisms are composed of elements.
• six elements— carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur —are basic to life and make up about 95% of the body weight of organisms.
• Atoms are the smallest particles of an element that display its properties.
• Elements and their atoms share the same name.
• Atoms consist of subatomic particles: protons (positively charged), neutrons (uncharged), and electrons (negatively charged).
• Protons and neutrons are located in the nucleus of the atom.
• An atomic symbol is a one- or two-letter notation used to represent a specific element, such as H for hydrogen, O for oxygen, or Na for sodium.
• Electron shells are regions around an atom's nucleus where electrons are likely to be found, with each shell representing a different energy level and distance from the nucleus.
• The nucleus of an atom contains protons and neutrons, while electrons move around the nucleus.
• Protons are positively charged, Neutrons are neutral and electrons are negatively charged.
• The atomic number is equal to the number of protons in each atom of an element
• The mass number of an atom is equal to the sum of the number of protons and neutrons in the nucleus.
• The atomic mass is approximately equal to the mass number.
• Atoms of an element are arranged horizontally by increasing atomic number in rows called periods.
• Atoms of an element arranged in vertical columns are called groups.
• Atoms within the same group share the same chemical binding characteristics.
• An isotope is a variant of an element that has the same number of protons but a different number of neutrons, resulting in a different mass number.
• The more distant the shell, the more energy it takes to hold in place.
• Electrons determine chemical behavior of atoms.
• Electrons in higher energy levels or shells are farther from the nucleus and have more energy.
• The Bohr model is a representation of an atom where electrons orbit the nucleus in fixed energy levels or shells.
• The first energy shell can hold up to 2 electrons.
• Each additional shell can hold up to 8 electrons.
• The valence shell is the outermost electron shell of an atom, which contains the valence electrons.
• The octet rule states that the outermost shell is most stable when it has eight electrons.
• Atoms that have their valence shells filled with electrons tend to be chemically stable.
• A Molecule is a group of two or more atoms bonded together by covalent bonds, forming the smallest unit of a chemical compound that retains its chemical properties.
• A compound is a substance composed of two or more different elements chemically combined in fixed proportions, forming a new substance with unique properties different from the individual elements.
• A formula tells the number of each kind of atom in a molecule.
• The process of bond formation is called a chemical reaction.
• Bonds between atoms are caused by the interactions between electrons in outermost energy shells.
• Bonds that exist between atoms in molecules contain energy.
• An ionic bond is a type of chemical bond formed when one atom donates electrons to another atom, resulting in the attraction between positively charged cations and negatively charged anions.
• An ion is an atom that has lost or gained an electron.
• A covalent bond is a type of chemical bond where two atoms share one or more pairs of electrons to achieve a stable electron configuration.
• Cations are positively charged ions formed when an atom loses one or more electrons.
• Anions are negatively charged ions formed when an atom gains one or more electrons.
• A nonpolar covalent bond is a type of chemical bond where two atoms share electrons equally, resulting in no charge separation within the molecule.