Ch. 5: The Structure of Matter – Study Guide
A mixture is different from a compound because each substance in a mixture retains its own properties. Unlike a
mixture, a compound has a chemical formula that is always the same.
The forces that hold different atoms or ions together are chemical bonds. Often atoms join so that each atom will have
an outermost energy level that is full of electrons. When two chlorine atoms bond, they share a pair of electrons.
Each molecule of hydrochloric acid, HCl, contains one atom of hydrogen and one atom of chlorine. Each molecule of
table sugar, C12H22O11, contains 12 atoms of carbon. The name dinitrogen tetroxide tells you that this compound
contains two N atoms and four O atoms.
The molecules in a solid have the strongest attractions to one another. Gases take up a lot of space because gas
molecules are not attracted to one another.
Copper is a good conductor of electricity because its electrons can move from atom to atom.
In a metallic bond, the nucleus of one atom is attracted by a nearby atom’s electrons. Covalent bonds are formed
between nonmetal atoms. In ionic compounds, the positively charged ions are formed from metal elements. Solid ionic
compounds have very high melting points because they contain charged ions that are locked tightly together.
Because polyatomic ions are made of covalently bonded atoms that have either gained or lost electrons, they behave
like simple ions.
The name for the compound with the formula CuBr2 would be written as copper (II) bromide. When copper combines
with oxygen to form copper (II) oxide, the charge of the copper ion is Cu2+.
Formaldehyde, CH2O, and acetic acid, C2H4O2, have the same empirical formula but different molecular formulas. It is
possible for different covalent compounds to have the same empirical formula because empirical formulas represent a
ratio of atoms in the compound. The simplest formula for a covalent compound is its empirical formula. A compound’s
molecular formula tells you how many atoms of each type are in one molecule.
Polymers are large organic molecules that are made of repeating units.
Carbon can form 4 chemical bonds with other atoms.