\documentclass{beamer}

\usepackage[utf8]{inputenc}

\usepackage{tikz}
\usetikzlibrary{arrows,overlay-beamer-styles}

\begin{document}

\begin{frame}
\begin{center}
\begin{tikzpicture}[>=stealth',thick]
\node at (0,0) (1) {$1$};
\node at (2,0) (2) {$2$};
\end{tikzpicture}
\end{center}
\end{frame}

\begin{frame}
\begin{center}
\begin{tikzpicture}[>=stealth',thick]
\node at (0,0) (1) {$1$};
\node at (2,0) (2) {$2$};
\draw (1) edge[bend left,->] (2);
\end{tikzpicture}
\end{center}
\end{frame}

\begin{frame}