Atoms & molecules

Atoms & molecules. abstract. .

We know that all matter is made of small particles called atoms and molecules. Different kind of atoms and molecules have different properties due to which different kinds of matter also show different properties. Thus, the properties of matter depend on the properties of atoms and molecules from which it is made..

Atoms. An atom is the smallest particle of an element. Atoms of most of the element are very reactive and do not exist in the free State (as single atoms). They exist in combination with the atoms of the same element or another element. There are as many kinds of atoms as are elements..

Atomic mass of an element. The atomic mass of an element is the relative mass of its atom as compared with the mass of a carbon 12 atom taken as 12 units. Carbon 12 atom is the atom of carbon which has 6 protons and 6 neurons in its nucleus so that its mass number is 12. The atomic masses of all other elements are determined by comparing the mass of their atom with the mass of a carbon 12 atom..

Molecules. A molecule is an electrically neutral group of two or more atoms chemically bonded together. A molecule is the smallest particle of a substance [element or compound] which has the properties of that substance and can exist in the free state ..

Molecular mass. Just like an atom has atomic mass , in the same way, a molecule has molecular mass. Molecular mass of a substance is the relative mass of its molecule as compared with the mass of a carbon 12 atom taken as 12 units. The molecular mass is equal to sum of the atomic masses of all the atoms present in one molecule of the substance..

Ions. An ion is a positive or negative charged atom or groups of atoms. An ion is formed by the loss or gain of electrons by an electron There are two types of ions : cations and anions..

Valency of ions. The valency of ion is equal to the charge of ions. If an ion has 1 unit of charge ,its valency is 1 and is called monovalent ions. If an ion has 2 unit of charge, its valency is 2 and is called divalent ions. If an ion has 3 unit of charge, its valency is 3 and is called trivalent ions ..

Gram atomic mass and gram molecular mass. The amount of a substance whose mass in gram in mass is numerically equal to it atomic mass/ molecular mass, is called gram atomic mass/ gram molecular mass of that substance. The molar mass of a substance is the mass of 1 mole of that atoms/ molecules. The molar mass of a substance has 6.022*10²³ atoms/ molecules of the substance in it..

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