gameobject goes in the wrong left and right directions

I've recently created a Sphere gameobject in Unity, and placed it on top of a Cube. I tried getting the Sphere to move left and right on the cube by pressing both the left and right buttons respectively. The problem I have is when i press left, the sphere rotates right, and when i press right, it rotates left. I just want the sphere to move in the direction im holding. Any advice?

 using UnityEngine;
 using System.Collections;
 
 public class SphereBehaviourScript : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
         
     }
     


     float rotationSpeed = 100.0f;
     
     // Update is called once per frame
     void Update () {
         float rotation = Input.GetAxis ("Horizontal") * rotationSpeed;
         rotation *= Time.deltaTime;
         rigidbody2D.AddTorque (rotation);
     }
 }

I'm a beginner to Unity, hopeful to learn as i go.