设\(\{a_{n}\}\)是等差数列，已知\(a_{3}=5\)，\(a_{5}+a_{7}=22\)，\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}.\)
\((Ⅰ)\)求\(\{a_{n}\}\)的通项公式及\(S_{n}\)；
\((Ⅱ)\)设\(b_{n}=\dfrac{1}{a_{n+1}^{2}-1}(n\in N^{*})\)，求数列\(\{b_{n}\}\)的前\(n\)项和．