How to create a table with cascaded rows

Question

I am unable to get the layout as shown also i am unable to get the ions in column 1. Na+ doesn't come the way it is required. Kindly help

This is what i wrote

\begin {tabular}{||c||c||c||}
\hline
\ Ion & SBF & HBP \\
\hline
 Na^{+} & 142 & 142 \\
 \hline
 K^{+} & 5 & 5 \\
 \hline
 Mg^{2+} &  1.5 & 1.5 \\ 
 \hline
\end{tabular}

Answer 1

This fixes what you've written:

\documentclass[a4paper]{article}
\usepackage{multirow}
\begin{document}
\begin{tabular}{|c|c|c|}
\hline

 \multirow{2}{*}{Ion} & \multicolumn{2}{|c|}{Concentration (mmol/dm$^3$)}\\
 \cline{2-3}
 & Simulated Body Fluid (SBF) & Human Blood Plasma (HBP) \\

\hline

Na$^{+}$ & 142 & 142 \\

\hline

K$^{+}$ & 5 & 5 \\

\hline

Mg$^{2+}$ & 1.5 & 1.5 \\

\hline
\end{tabular}
\end{document}

You can add the remaining rows.