[Tex/LaTex] Add equation number in array

arraysequationsnumbering

I'm struggling with aligning my equations and provide a number for them. I googled but haven't found a solution for the array environment.
I tried the align env. but only with the array env. I managed to get the result I was looking for.
Now I want to label the two conversation equations at the end of the line (preferably vertically centered).

\documentclass[12pt,a4paper]{scrartcl}
\usepackage{amsmath}
\usepackage{amssymb,amsthm}
\begin{document}
\begin{equation}
\begin{array}{lrcl}
\textbf{Conservation of energy}     & E_{kin}               &=& E'_{kin}                \\
                & m_1 v_1^2 + m_2 v_2^2         &=& m_1 {v'}_{1}^{2} + m_2 {v'}_{2}^{2} \\
                & m_1 (v_1^2 - {v'}_1^2)        &=& m_2 ({v'}_2^2 - v_2^2)      \\
                & m_1 (v_1 + {v'}_1) (v_1 - {v'}_1)     &=& m_2 ({v'}_2 + v_2) ({v'}_2 - v_2)   \\
\\

\textbf{Conservation of momentum}   & p                 &=& p' \\
                & m_1 v_1 + m_2 v_2             &=& m_1 {v'}_1 + m_2 {v'}_2\\
                & m_1 (v_1 - {v'}_1)            &=& m_2 ({v'}_2 - v_2)\\
\end{array}
\end{equation}
\end{document}

To make it clearer: I want the black number to be gone and the red numbers to appear:

Screenshot with added numbers

Best Answer

enter image description here

amsmath has several environments designed to number each row, or as here number the group as a whole. Do not use array for such display constructs the spacing and style are not designed for that.

\documentclass[12pt,a4paper]{scrartcl}
\usepackage{amsmath}
\usepackage{amssymb,amsthm}
\begin{document}

\textbf{Conservation of energy}
\begin{equation}
\begin{split}
  E_{\mathrm{kin}}                  &= E'_{\mathrm{kin}}                   \\
  m_1 v_1^2 + m_2 v_2^2             &= m_1 {v'}_{1}^{2} + m_2 {v'}_{2}^{2} \\
  m_1 (v_1^2 - {v'}_1^2)            &= m_2 ({v'}_2^2 - v_2^2)              \\
  m_1 (v_1 + {v'}_1) (v_1 - {v'}_1) &= m_2 ({v'}_2 + v_2) ({v'}_2 - v_2) 
\end{split}
\end{equation}

\textbf{Conservation of momentum}  
\begin{equation}
\begin{split}
  p                  &= p'                      \\
  m_1 v_1 + m_2 v_2  &= m_1 {v'}_1 + m_2 {v'}_2 \\
  m_1 (v_1 - {v'}_1) &= m_2 ({v'}_2 - v_2)
\end{split}
\end{equation}


\end{document}
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