Abstract
Masses and decay constants of mesons containing a single
c
or
b
quark are described within the framework of heavy-quark symmetry. The
B
∗
s
−
B
s
and
B
¯
∗0
−
B
¯
0
mass splittings are found equal to within a fraction of an MeV. Decay constants of
D
and
B
mesons are estimated using isospin mass splittings in the
D
,
D
∗
,
B
, and
B
∗
states to isolate the electromagnetic hyperfine interaction between quarks. A relation following from the use of splittings in kaons is also considered.