  Recently, the LHCb Collaboration reported three $P_c$ states in the
${J/\psi}p$ channel. We systematically study the mass spectrum of the hidden
charm pentaquark in the framework of an extended chromomagnetic model. For the
$nnnc\bar{c}$ pentaquark with $I=1/2$, we find that (i) the lowest state is
$P_{c}(4327.0,1/2,1/2^{-})$ [We use $P_{c}(m,I,J^{P})$ to denote the
$nnnc\bar{c}$ pentaquark], which corresponds to the $P_{c}(4312)$. Its dominant
decay mode is $\Lambda_{c}\bar{D}^{*}$. (ii) We find two states in the vicinity
of $P_{c}(4380)$. The first one is $P_{c}(4367.4,1/2,3/2^{-})$ and decays
dominantly to $N{J/\psi}$ and $\Lambda_{c}\bar{D}^{*}$. The other one is
$P_{c}(4372.4,1/2,1/2^{-})$. Its dominant decay mode is $\Lambda_{c}\bar{D}$,
and its partial decay width of $N\eta_{c}$ channel is comparable to that of
$N{J/\psi}$. (iii) In higher mass region, we find $P_{c}(4476.3,1/2,3/2^{-})$
and $P_{c}(4480.9,1/2,1/2^{-})$, which correspond to $P_{c}(4440)$ and
$P_{c}(4457)$. In the open charm channels, both of them decay dominantly to the
$\Lambda_{c}\bar{D}^{*}$. (iv) We predict two states above $4.5~\text{GeV}$,
namely $P_{c}(4524.5,1/2,3/2^{-})$ and $P_{c}(4546.0,1/2,5/2^{-})$. The masses
of the $nnnc\bar{c}$ state with $I=3/2$ are all over $4.6~\text{GeV}$.
Moreover, we use the model to explore the $nnsc\bar{c}$, $ssnc\bar{c}$ and
$sssc\bar{c}$ pentaquark states.
