Nature: Matter and Energy
Nature is not just our immediate surrounding or environment, but is the whole Universe of Cosmos. Study of the origin and topography of cosmos is called Cosmology. The cosmos is an orderly complex of innumerable stars and planets, scattered in a space filled with gas hydrogen helium and neon and micron sized dust grains, It is all made up of Matter, and Energy everything existing in nature large or small living or nonliving is formed of matter, and all forces like magnetism gravitation. Sound, heat, electricity, light etc. operating in nature and causing natural events to occur, are differnet manifestations of energy. Thus we can define nature as a Complex Chemical physical System"
Definition and physical states of matter: Matter is anything that occupies space, possesses mass, and can be perceived by our visual and other sensei exists in nature in three usually interconvertible physical states.viz solids liquids and gases. For instance, ice water and steam are respectively the solids, liquids and gaseous states of water.
Structural organization of matter: This consists of three grading laves viz., subatomic, atomic and molecular. At the lowest, subatomic level protons, neutrons and electrons are the ultimate particulate units of matter .Independent subatomic units are nonexistent upon the earth .Tightytly bound together in variable numbers by means of energy .these units form the second stage units of matter organization called atomic, The force or energy .binding the subatomic particles into atoms, called atomic energy , is obviously the energetic unit of matter. Free aroma also do not occur in earthrises matter but these are the smallest active units easily transferable form one kind of matter to the in chemical reactions .Thus atoms are to be regarded as the primary reactive units of earth present matter .So have recognized 112 types ofatoms.92 present unearth matter and 20 prepared artificially, but might be present elsewhere in the vast universe.
According to modern hypothesis, the structure of an atom is based upon wave Nature of its electrons. it spells out that each atom has two main parts the positively charged nucleus, containing protons and neutrons, and a three dimensional space around it, in which negatively charged electrons and incessantly move about at high velocities in definite orbits called the shells. The protons of the nucleus are positively charged, while the neutrons are neutral. It is these particles which form the major mass of the atom. Since protons and electrons are in equal number, the atom itself remains neutral.
Hydrogen atom is the simplest in structure, its nucleus possesses a single proton, but neutron, and accordingly, there is a single shell of single electron. All other atoms contain neutrons also, and more than one protons and electrons, the latter in, ore than one shells except is case of Helium.