Text: Atomic structure of matter

The building blocks of matter are atoms. Atoms are approximately spherical with diameters of the order of 10 – 10 ??? m. They consist of a minute, dense, positively charged nucleus. The nucleus consists of heavy, uncharged neutrons and positively charged protons of nearly equal mass. Around the nucleus there is a cloud of light (approximately 10-27g), negatively charhed electrons. As isolated atoms are electrically neutral, the number of electrons is equal to the number of protons in the nucleus.

Atoms may associate and form a specific material. Ice (a solid), water (a liquid), and water vapour (a gas) are examples of three states matter