Ch 2: Atoms, Molecules, and Ions
Modern view of atomic structure
 Review protons, neutrons, and electrons
 Every atom has an equal number of electrons and protons, no net electrical charge
 Where is most of the mass of an atom contained?
 What makes an atom of one element different from an atom of another element?
 What is an elements atomic number?
o The number of protons in the nucleus of an atom of any particular element
o Also number of electrons in a neutral atom
o How elements are arranged on the periodic table
 What is mass number?
o Total number of protons and neurons
𝑚𝑎𝑠𝑠 #
o 𝑎𝑡𝑜𝑚𝑖𝑐
#𝑠𝑦𝑚𝑏𝑜𝑙
 What are isotopes?
o Atoms with the same number of protons different number of electrons
o Same atomic numbers different mass numbers
o Many times atomic number is omitted and isotopes are just written 12C or carbon12
Atomic weights
 How do elements occur in nature?
o As mixtures of isotopes
 How do you determine average atomic mass?
o (Percent abundance x mass of that isotope) + (Percent abundance x mass of that
isotope)+ ….. =average atomic mass
o Where is average atomic mass listed or found?
o Maybe to practice problem on how to find AAM
Periodic Table
 What can you tell me about how the periodic table is arranged?
o Similar elements grouped into columns
o Elements ordered in increasing atomic number
o Alkali metals first column
o Alkali earth metals second column
o Halogens second to last column
o Noble gasses last column
o Metals are on the left side (hydrogen not a metal)
o Nonmetals on right side
o Sides divided by diagonal, step-like line, running from boron to astatine. These
are called metalloids
 Rows are called periods
 Columns are called groups or families
o Different labeling schemes are used to label these
o Elements in the same group exhibit similar qualities
Molecules and molecular compounds
 What is a diatomic molecule?
o A molecule that is made up of two atoms
o BrINClHOF
 What is the difference between empirical and molecular formulas?
o Molecular formulas indicate the actual numbers and types and atoms in a
molecule. Empirical formulas only give the relative number of atoms of each
type in a molecule. Subscripts are always the smallest possible whole-number
ratios.
o C2H4 vs. CH2
o By knowing the molecular formula you can determine the empirical formula, the
opposite is not true
 What is the structural formula?
o Shows which atoms are attached to which within the molecule
o Usually doesn’t depict the actual geometry of the molecule
 Various models are used to help visualize molecules
Ions and Ionic compounds
 What are polyatomic ions?
o Atoms joined as in a molecule, but they have a net positive of negative charge
 When atoms gain a charge what determines what charge they take?
o Valence electrons
o Want a full outer shell
 What is an ionic compound?
o A compound that contains both positively and negatively charged ions
o Sodium Chloride
o Combination of metals and nonmetals
Naming inorganic compounds
 How do we name type I binary compounds?
o Name the ions, anion include –ide suffix
o Metal and nonmetal, metal has known charge
 How do we name type II binary compounds?
o Name both parts include roman numerals to indicate charge and –ide suffix on
anion
o Metal and nonmetal, metal’s charge is not known
 How do we name type III binary compounds?
o Name each part using proper prefixes
o Two nonmetals
 How do we name polyatomic anions containing oxygen?
o Ending –ate or –ite
o –ite assigned to polyatomic ion with lower oxygen content
o Nitrate vs. nitrite
 How do we name acids containing anions whose names end in –ide? (don’t contain
oxygen)
o Change –ide ending to –ic and add hydro prefix

How do we name acids containing anions whose names end in –ate or –ite? (do contain
oxygen)
o Change –ate to –ic and –ite to –ous
Some simple organic compounds
 What are hydrocarbons?
o Compounds that contain only carbon and hydrogen
 What are alkanes?
o The most basic class of hydrocarbons, each carbon atom is bonded to four other
atoms
 How do we name alkanes?
o –ane ending, first four methane, ethane, propane, butane, then named for number
of carbons
 What is an alcohol?
o Occurs when an H atom of an alkane is replaced with an –OH group
 How do we name alcohols?
o Add –ol ending
 When do we add a number out front when naming alcohols?
o When the chain is 3 carbons or longer