chemistry module 3

• a chemical bond is a link b/w two atoms resulting from the mutual attraction of ions.
• calibert lewis believed that the outer shell of electrons is the key to chemical bonding
• octet rule states that atoms of all elements have between 1 and 8 electrons in the outermost valence shell (exception is hydrogen and helium)
• valence electrons are electrons in the outermost shell that can be lost or shared with another atom
• ionic bonds form electrostatic attraction between positive and negative ions. electrons are given up by one atom and gained by another atom, then those atoms are attracted to each other
• in covalent bonds electrons are shared between two atoms, neither completely gaining or losing electrons.
• nonmetals form covalent bonds with each other
• metals and nonmetals form ionic bonds with each other
• to find the valence electron in electron configuration, find the highest levels and count how many electrons
• an inert atom has all 8 electrons in the outermost shell and doesnt seek to form bonds
• sublevels s and p are where most valence electrons are found
• binary ionic compound is an ionic bond with a positive charge (cation) and a negative charge (anion). metals are the cation and nonmetals are the anion
• polyatomic ions are a charged group of covalently bonded atoms that can bond with metals, nonmetals, or polyatomic ions ionically.
• in binary nomenclature, the first element is the cation (metal), so dont change the ending. the second element is the anion (nonmetal) or a polyatomic anion, so change the ending to -ide. e.g oxygen > oxide
• to name a binary covalent compound, add a prefix to the name of the first element to show the no. of atoms of the element in the bond. then add a prefix to show the no. of atoms of the second element to the root of the second element name. lastly, add the ending -ide to the last element.
• a binary compound is where hydrogen is combined with a second nonmetallic element thats not oxygen
• ionic compounds are solid at room temperature
• ionic crystals are hard, have high melting points, brittle, non-conductive in solid state, and conductive in molten and aqueous state
• a formula unit is a chemical formula of an ionic compound
• to write a formula unit, identify the charges of each ion, write the cation first, criss cross the charges, then simplify if needed
• in metallic bonds, electrons are constantly trying to move from one atom to the other. thats why metals are good conductors of heat
• diatomic molecule is composed of only 2 atoms of the same or different chemical elements. e.g O2
• there are only 7 diatomic molecules that have covalently bonded with each other. iodine, bromine, chlorine, fluorine, oxygen, nitrogen, and hydrogen
• covalent bonds are soft and have a low boiling point. ionic bonds are brittle and have a high boiling point
• nonpolar covalent bonds are atoms that have an equal attraction for the shared electron
• polar covalent bonds are atoms that have unequal attraction for the shared electron
• vsepr theory is used to predict the geometry and shape of a molecule
• vsepr (electron)geometry of a molecule is determined by the no. of bonded electrons and lone pair electrons around the central atom
• molecular shape is the general shape of the molecule based only on the bonded atoms and excludes lone pairs
• the no. of domains is the sum of bonded atoms and lone pairs of electrons around the central atom.
• intramolecular forces are INSIDE an atom and holds it in place together
• intermolecular forces are outside an atom and between molecules that hold them together
• ionic compounds have the highest melting and boiling points
• polar covalent compounds have a lower melting and boiling point than ionic compounds, but higher than nonpolar covalent compounds