Instantiate prefab randomly but not in already genrated position

I want to generate bubble randomly in my screen.When bubble is generated in one place then other bubble can not generated near of its radius 1 area. means bubbles can not collide or triggered with any other bubbles.

How can i do it ?

public void GenerateBubble ()
				newBubbleXPos = Random.Range (-7, 7);
				newBubbleYPos = Random.Range (-3, 3);
				bubbleClone = (GameObject)Instantiate (bubblePrefab, new Vector3 (newBubbleXPos, newBubbleYPos, 0), Quaternion.identity);
				bubbleList.Add (bubbleClone);
				if (bubblePosList.Contains (bubbleClone.transform.position)) {
					bubbleClone.transform.position=new Vector3(Random.Range (-7,7),Random.Range (-3,3),0);
				bubblePosList.Add (bubbleClone.transform.position);
				bubbleClone.transform.parent = UIManager.instance.CurrentLevel.transform;

In this my code every bubble is generated in different position but it can collide with other bubble means i want to generate new bubble not same position as well as it can not collide also. My bubble collider’s radius is 1.

Each time you want to generate a new bubble:

  1. Choose a random Vector3 position (using Random.Range)
  2. Call Physics.OverlapSphere to see whether the chosen position touches any colliders.
  3. If no colliders are touched (i.e. OverlapSphere returns false), generate a bubble at this location, otherwise return to 1 and generate a new random location.

I have found Answer :

    public List<GameObject> bubbleList = new List<GameObject> ();
    private int newBubbleXPos;
    private int newBubbleYPos;

public void GenerateBubble ()
        bool locationInvaild = true;
        while (locationInvaild) {
            newBubbleXPos = Random.Range (-8, 8);
            newBubbleYPos = Random.Range (-4, 4);
            currentPosition = new Vector3 (newBubbleXPos, newBubbleYPos, 0);
            locationInvaild = false;
            for (int i=0; i<bubbleList.Count; i++) {
                if (Vector3.Distance (bubbleList _.transform.position, currentPosition) < 2.5f * radius) {_

locationInvaild = true;
bubbleClone = Instantiate (bubblePrefab, new Vector3 (newBubbleXPos, newBubbleYPos, 0), Quaternion.identity) as GameObject;
bubbleList.Add (bubbleClone);