Learning Idea

Molecule: The smallest particle of a substance that can exist independently is called a molecule. For example H 2 , O 2 , Cl 2 ,. A molecule consists of one or different kinds of atoms, for example, P 4, S 8 , NH 3 , H 2 SO 4 , C 6 H 12 O 6. Monoatomic molecule:  A molecule that contains one atom is called a monoatomic molecule . For example, He, Ne, Ar, Kr, Xe, and Rn. Diatomic molecule:  A molecule that contains two atoms is called a Diatomic molecule . For Example H 2 , O 2 , Etc. Triatomic molecule:  A molecule that contains three atoms is called a Triatomic molecule . For Example: CO 2 , H 2 O, SO 2 etc. Atomicity: The total number of atoms in a molecule is called atomicity. For example, the atomicity of He is one, the atomicity of H 2 is 2, and the atomicity of H 2 O is 3. Macromolecule:  A big molecule that contains a very large number of atoms is called a macromolecule. For example Haemoglobin, Chlorophyll. Hemoglobin is found in the blood. I...

  Atom Atom: Greek philosophers thought that matter is made up of individual particles which cannot be further subdivided. Democritus (460-370) called these indivisible particles an atom (the Greek word atom means indivisible.) In 1880 , an English school teacher John Dalton gave atomic theory. Its main points are given below. 1     All matter is composed of atoms. 2.   The atoms of the same elements have similar properties. 3.   The atoms of different elements have different properties. The modern definition of an atom is given below. The smallest particle of an element that may or may exist independently is called an atom. For example, He, Ne, H, C, Na, Cu, S, etc. Modern research shows that an atom is further composed of electrons, protons, neutrons, positrons, hyperons, neutrinos, anti-neutrino, etc. they are called sub-atomic particles. More than 100 sub-atomic particles have been discovered. But electrons, protons, and neutrons are the fund...

Determination of Atomic masses by mass spectrometry An instrument that measures the exact masses of different isotopes of an element is called a mass spectrometer and this technique is called mass spectrometry. First of all Aston’s mass spectrometer was used to identify the isotopes of an element. The Dempster’s mass spectrometer is used to identify isotopes of solid elements. The principle of the mass spectrometer is that the positive ion of each isotope has its own (m/e) value. The isotopes are separated based on their mass-to-charge ratio (m/e). Construction and Working: The substance (isotopic element) under analysis is converted into vapuors and is kept very low (10 -6 to 10-7 torr). These vapours enter an ionization chamber. Here fast-moving electrons collide with vapours. Thus vapours are ionized. Different isotopes produce different ions with different (m/e) values. These positive ions are accelerated by applying a potential difference of 500-200 volts to the perfora...