composition of matter in chemistry
ATOM An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element . Every solid , liquid , gas , and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale). Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, for example - gives noticeably incorrect predictions due to quantum effects . Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Most of the Universe consists of matter and energy . Energy is the capacity to do work. Matter has mass and occupies space. All matter is composed of basic elements that cannot b...