Chem2

• Atom


  The smallest identifiable unit of an element, a generally neutral particle made of negatively charged electrons moving around a positively charged nucleus
• Subatomic particles


  • Protons
  • Neutrons
  • Electrons
• Protons


  • Reside in the nucleus, carry a positive charge
• Neutrons


  • Reside in the nucleus, carry a neutral charge
• Electrons


  • Occupy the volume surrounding the nucleus, carry a negative charge, have a smaller mass than protons and neutrons
• Atomic number


  The number of protons in an atom, identifies the element
• Mass number


  The total number of protons and neutrons in an atom
• Isotopes


  Atoms of the same element that have a different mass number due to a different number of neutrons
• In ordinary chemical reactions, the nucleus does not change, only the number of electrons changes
• Ion


  A charged particle resulting from the number of protons not being equal to the number of electrons
• Mechanisms of reactions


  Movements of electrons at the fundamental level
• Ion


  A charged particle resulting from the fact that the number of protons is not equal to the number of electrons
• Cation


  Atom with a positive charge because it has lost an electron
• Anion


  Atom with a negative charge because it has gained an electron
• It is important to pay close attention to whether a particle is a charged ion or a neutral ion because an ion possesses properties that are different from those of a neutral molecule
• Atomic mass unit (amu)


  Unit of mass defined relative to a carbon-12 atom, where one amu is exactly 1/12 the mass of a single carbon-12 atom
• The atomic weight of an element is the weighted average of the isotopic masses of the element's naturally occurring isotopes
• Calculating atomic weight


  Multiply percent abundance of each isotope by its atomic mass, then add the results
• Periodic table


  • Separates metals and non-metals
  • Metals are good conductors, malleable, ductile, lustrous, tend to lose electrons
  • Non-metals are not conductive, not malleable, not lustrous, tend to gain electrons
  • Elements in vertical columns (groups) have similar properties
  • Elements in horizontal rows (periods) have increasing atomic number
• Main group elements


  Elements in groups 1, 2, and 13-18
• Transition metal elements


  Elements in groups 3-12
• Alkali metals


  Group 1 elements, very reactive and readily lose electrons
• Cars and some electronics even in medicine like medical imaging tools use lanthanides and actinides
• Lanthanides and actinides tend to be radioactive
• The focus of this session is not on lanthanides and actinides
• Alkali metals


  Group 1 elements, very reactive and always ready to lose an electron to form +1 cations
• Alkaline earth metals


  Group 2 elements, form +2 cations
• Halogens


  Group 17 elements, form diatomic molecules and react with metals to form -1 anions
• Noble gases


  Group 18 elements, extremely stable and unreactive due to full valence electron shells
• Groups 3-12 are called transition metals
• The lanthanide series and actinide series are separate from the main groups
• Molecule


  A separate, distinct, electrically neutral group consisting of a well-defined number of atoms held together by chemical bonds
• Ionic compound


  Oppositely charged ions held together in an ordered 3D crystal lattice structure
• To determine if a compound is ionic or molecular: if both elements are nonmetals, it is molecular; if one element is a metal and the other is a nonmetal, it is ionic
• Monatomic cations


  • Alkali metals (Li-Fr)
  • Alkaline earth metals (Be-Ra)
  • Al3+
  • Zn2+
  • Ag+
• Fixed charge cations


  Metals that always form the same ion by losing the same number of electrons
• Variable charge cations


  Metals that can form more than one type of cation by losing different numbers of electrons
• Roman numerals


  Used to differentiate variable charge cations, e.g. Fe2+ vs Fe3+
• Monatomic anions


  Formed when nonmetal atoms acquire additional electrons, named by changing the element ending to -ide
• Important polyatomic anions ending in -ide

  • CO3^2- (carbonate)
  • SO4^2- (sulfate)
  • PO4^3- (phosphate)
  • NO3- (nitrate)