These are aluminum atoms. An atom is the smallest particle of an element that has the properties of that element. Some properties of aluminum are: shiny, silver colored, fragile, and thin. Each element has its own type of properties. Chemists use symbols to represent elements.
1 A person who has passed away and who is no longer alive is someone who would be described as dead.  When your career has faltered, you've been fired and have no hope of gaining your position back, this is an example of a time when your career is dead.
Dead, in the sense of lifeless, is so commonly used that we tend to ignore its other meanings. The meaning that's relevant here is exact or precise. This is demonstrated in many phrases; 'dead shot', 'dead centre', 'dead heat', etc. So, 'dead ringer' is literally the same as 'exact duplicate'. It first came into use soon after the word ringer itself, in the US at the end of the 19th century.