  Two-body charmless nonleptonic decays of the B_s meson are studied within the
framework of generalized factorization in which factorization is applied to the
tree level matrix elements while the effective Wilson coefficients are $\mu$
and renormalization scheme independent, and nonfactorizable effects are
parametrized in terms of N_c(LL) and N_c(LR), the effective numbers of colors
arising from (V-A)(V-A) and (V-A)(V+A) four-quark operators, respectively.
Branching ratios of $B_s\to PP,PV,VV$ decays are calculated as a function of
N_c(LR) with two different considerations for N_c(LL). We find that (i) the
electroweak penguin contributions account for about 85% (for N_c(LL)=2) of the
decay rates of $B_s\to \eta\pi,\eta'\pi,\eta\rho,\eta'\rho,\phi\pi,\phi\rho$,
which receive contributions only from tree and electroweak penguin diagrams; a
measurement of them will provide a clean determination of the electroweak
penguin coefficient a_9, (ii) electroweak penguin corrections to $B_s\to\omega
\etapp,\phi\eta,\omega\phi,K^{(*)}\phi,\phi\phi$ are in general as significant
as QCD penguin effects and even play a dominant role; their decay rates depend
strongly on N_c(LR), (iii) the branching ratio of $B_s\to \eta\eta'$ is of
order 2x10^{-5}, (iv) the contribution from the $\eta'$ charm content is
important for $B_s\to\eta'\eta'$, but less significant for $B_s\to\eta\eta'$,
and (v) the decay rates for the final states $K^{+(*)}K^{-(*)}$ follow the
pattern: $\Gamma(B_s\to K^+K^-)>\Gamma(B_s\to K^+K^{*-})\geq\Gamma(B_s\to
K^{*+}K^{*-}) >\Gamma(B_s\to K^{+*}K^-)$, as a consequence of various
interference effects between the penguin amplitudes governed by the
coefficients a_4 and a_6.
