INTRODUCTION / DEFINITIONS.
Canal rays also called anode rays, are seen moving from the anode towards the cathode in the specially designed discharge tube.
According to Thomson’s Model of an atom, an atom may be regarded as a positively charged sphere in which protons are present. The negatively charged electrons are believed to be studded or embedded in the sphere.
The nucleus of atom is positively charged according to Rutherford’s model of an atom. All the protons in an atom are therefore, present in the nucleus.
In the extra nuclear portion of an atom, the electrons revolve in well defined circular paths known as orbits.
These circular orbits are also known as energy levels or energy shells.While revolving in an orbit, the electron is not in a position to either lose or gain energy.
As the electrons have negligible mass, the entire mass of the atom is that of protons and neutrons present in its nucleus. Since each proton and neutron has mass equal to 4 u, therefore, mass of an atom must be the same as the sum of protons and neutrons present in the nucleus.
Valency of an element may be defined as the combining capacity of its atom with atoms of other elements
The mass number of an element may be defined as : the sum of the number of protons and neutrons present in the nucleus of its atom.
Isotopes may be defined as the different atoms of the same element having same atomic number but different mass numbers.
Isobars may be defined as the atoms belonging to the different elements with same mass numbers but different atomic numbers.
Electron is known as universal particle.
Radius of extra nuclear portion is nearly 105 times more as compared to the nucleus.
Chlorine always exists as two isotopes. These are Cl-35 and Cl-37 isotopes
Proton (H+) is formed when hydrogen atom also called protium, loses an electron.
The atoms is neutral. One unit positive charge on proton cancels with one unit negative charge on electron.
Protons and neutrons present in the nucleus determine the mass of an atom.
The outermost energy shell in an atom can have a maximum of eight electrons.
According to Thomson’s model of an atoms, all the protons in an atom are present in the positively charged sphere while negatively charged electrons are studded in this sphere.
Since the electrons and protons are equal in number each carrying one unit charge, the atom as a whole is electrically neutral.
Hydrogen atom has no neutron.
Cathode rays always travel in straight line.
Isotopes of an element have same atomic number as well as electronic distribution.
Since the chemical properties of the elements are related to their electronic distribution or configuration, the elements with similar configuration have similar properties.
Alpha particles have positive charge