Structures and floating point variables (repost with code tags)

I have a problem with floating point variables with structures. When I try to enter a floating point number, it seems to put it in the firstName string array. I don't know why, the code and output is posted below. Please help if you can, I would greatly appriciate it.

Output:
Josh Haynes 0.00
3.45 Haire 0.00

Code:

---

// char firstName[20]
// char lastName[20]
// float gpa
// int ID
void Manual_Input()
{
  int count, loop_counter; 
  printf ("How many students do you want to enter?: ");
  scanf ("%d", &count);
  student_array = (students *) malloc (count * sizeof(students));
  for (loop_counter = 0; loop_counter < count; loop_counter++)
  {
    printf ("Enter first name: ");
    scanf ("%s", student_array->firstName);
    printf ("Enter last name: ");
    scanf ("%s", student_array->lastName);
    printf ("Enter GPA: "); 
    scanf ("%.2f", student_array->gpa);
    student_array->ID = loop_counter;
    student_array++;
  }
  student_array -= count;
  printf ("Number of students are %d.\n", count);
  for (loop_counter = 0; loop_counter < count; loop_counter++) 
  {
    printf ("%s", student_array->firstName);
    printf (" %s ", student_array->lastName); 
    printf ("%.2f\n", student_array->gpa);
    student_array++;
  }
  free (student_array);
  return;
}

---

Code:

---

for (loop_counter = 0; loop_counter < count; loop_counter++)
                                          {
                                            printf ("Enter first name: ");
                                            scanf ("%s", student_array->firstName);
                                            printf ("Enter last name: ");
                                            scanf ("%s", student_array->lastName);
                                            printf ("Enter GPA: "); 
                                            scanf ("%2f", student_array->gpa); //I deleted the . and it worked better but I didn't use pointers, so my scanf line wase scanf(" %2f",&student_array[loop_counter].gpa); so i don't know if it will be the same but hopefully that's all
                                            student_array->ID = loop_counter;
                                            student_array++;
                                          }

---

> scanf ("%.2f", student_array->gpa);
should be
scanf ("%f", &student_array->gpa);