Chapter5-chemicalreactions：5章化学反应.docx

Chapter 5- Atoms and Bonding NotesCUE WORDS or QUESTIONSNOTES WRITTENWhat are valence electrons?Valence electrons the electrons furthest away from the nucleus (so they X have the highest energy level) The number of valence electrons determines the properties of that element (including the ways in which the atom can bond with other atoms)How to create an electronElectron dot diagram figure that shows the number of valence electrons dot diagram- in an element Includes the element symbol, surrounded by dots (representing the valence electrons) Atoms are more stable (less likely to react) when they have 8 valence electrons (besides He which is happy with 2!)Electron Dot Diagram Examples: Li Be B C N O F NeAtoms gain or lose electrons in order to have 8 valence electronsChemical Bond the force of attraction that holds two atoms together X What creates an ion?Ion an atom or group of atoms that has become electrically charged, because the atom lost or gained electronsWhen an atom loses an electron it has a positive chargeWhen an atom gains an electron it has a negative chargePolyatomic Ion ions that are made of more than one atom Poly means many, polyatomic means many atomsHow are ionic bonds made?Ionic Bond the attraction between two oppositely charged ions (positive and negative attract!)Ionic Compound atoms that are bound together due to their charges, usually form between a metal and a nonmetal Chemical Formula combination of symbols that shows the ratio of elements in a compound Ex. MgCl2 or NaCl or K2SSUMMARY XNOTES WRITTENCUE WORDS or QUESTIONSWhen ionic compounds form, the ions come together in a way thatbalances out the charges on the ions (so there is no net charge) XHow are ionic compounds Subscript small number written after an element that indicates the number written? of an element in a chemical formula Ex. MgCl2 - 1 Magnesium ion with 2 Chlorine ionsThe name of the positive ion goes first, then the name of the negative ionn If the negative ion is an element, add the ending iden If the negative ion is polyatomic, the name ends in ate or -ite Ex. Mg2+ + O2- MgO Magnesium oxide Ex. Na+ + NO3- NaNO3 Sodium nitrate What are the properties of Properties of ionic compounds are: ionic compounds? Crystal Shape orderly 3-D shape High Melting Point ionic bonds are strong Electrical Conductivity when dissolved in water, ionic compounds conduct electricityHow are covalent bondsCovalent Bond a chemical bond formed when two atoms share electrons X different from ionicMolecular compound- atoms that are bound together because of they are bonds? sharing electrons, usually forms between nonmetalsUse electron dot diagrams to set up an atom to have 8 valence electronsElectrons can be shared in order to fulfill the octet rule (8 valence electrons)Can an atom share more thanDouble Bond two pairs of electrons being shared between two atoms one electron?Triple Bond three pairs of electrons being shared between two atomsWhat are the properties of Properties of molecular compounds are: covalent molecules? Low melting point and boiling points Do no conduct electricity when dissolved in waterWhat hap