int LEDpins[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11}; 
//global variable array to assign each of the LEDs to a pin
int ledCount = 10; //initiailising for use in the for loop

//use a for loop to setup each LED to maximise code efficiency
void setup() {
  for (int thisLED = 0; thisLED < ledCount; thisLED++){
    pinMode(LEDpins[thisLED], OUTPUT); //thisLED is used as an array index for ledPins 
  }
  //Turn off all the LED pins
  for (int thisLED = 0; thisLED < ledCount; thisLED++){
    digitalWrite(LEDpins[thisLED], LOW);
  }
}

void loop() {
  //Turn on all the LEDs
  for (int thisLED = 0; thisLED < ledCount; thisLED++){
    digitalWrite(LEDpins[thisLED], HIGH);
    delay(100);
  }
}