Hold space bar and jump [2D]

So my problem here is that when the player holds the space button the addForce function is increased which I don't want.

So what I want is that if a player holds the space button they can keep jumping continuously if they're on the ground...

Here is my code:

     private void Update()
     {
         GetComponent<Rigidbody2D>().velocity = new Vector2(1.0f * movementSpeed, GetComponent<Rigidbody2D>().velocity.y);
 
         if (IsGrounded() && Input.GetKey(KeyCode.Space)) 
         {
 
             Debug.Log("IS JUMPING");
             _rigidBody.AddForce(new Vector2(0, jumpForce), ForceMode2D.Impulse);
         }
     }