If you set up an edge collider on the objects you can use 

 void Update()
 {
 //this detects the mouse position
 Vector2 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
 //this check to see if the mouse is over the collider documentation below
 if (this.GetComponent<EdgeCollider2D>().ClosestPoint(mousePos) == mousePos)
 {
 print("mouse is hovering over object");
 if
 {
}
 }
 }

documentation https://docs.unity3d.com/ScriptReference/Collider.ClosestPoint.html