An animation representing positively charged nuclei in a cloud of delocalised electrons. Each nucleus is represented by a circle with a plus symbol (‘+’) in it. The nuclei are arranged in staggered rows. That is, each row of circles in alternate rows are offset by half a circle, to the left or the right, so that they fit in between the circles in the adjacent rows. The electrons in the outer shells are represented by blue circles that are moving freely (animated) between the nuclei to indicate their delocalisation. Each nucleus is represented by an orange sphere with ‘+’ in it. The 16 nuclei are arranged in four staggered rows of four orange spheres that are static. Each sphere in the second and fourth rows has been shifted horizontally so that it is above the space between adjacent spheres in the first and third rows. The electrons are represented by blue spheres that are moving freely to indicate their delocalisation.