Cathode ray definition series#

The high voltage provides energy for the atoms of a gas to further split or break up. The changes that occur in the discharge tube at different pressures were observed. The electrodes are connected to high voltage for the current to flow. The electrode connected to the positive terminal is known as anode and the electrode connected to the negative terminal is known as cathode. These electrodes are connected to positive and negative terminals of a battery. These metal plates are called electrodes. The discharge tube consists of a glass tube from which most of the air has been evacuated having two metal plates sealed at both the ends. These tubes, as modified by Sir William Crookes, became the first to produce cathode rays, leading eventually to the discovery of the electron. In 1855, The German inventor Heinrich Geissler developed the mercury pump and produced the first good vacuum tubes.

Cathode ray definition series#

Along the way a series of discoveries were made which led to the technological revolution of the 20 th Century. The answers to these questions, and to the basic structure of matter, were resolved by experiments that began with the study of electric discharges in evacuated tubes. Even the basic question of whether the charge of the particles was positive or negative remained undetermined. Similarity : Atom is the smallest unit of matter that takes part in a chemical reaction.Īlthough many of the pioneers of 19 th century physics, including Faraday, were convinced on the basis of chemistry and the phenomena observed in electrolysis that electric current consisted of the flow of particles of charge, the nature of these charges was not understood.

The molecules of proteins are highly complex. For example, atoms of argon and calcium have same atomic weight.Ītoms combine in small whole numbers to form compound atoms (molecules).Ītoms in organic compounds do not combine in small whole number ratio. It means some of the atoms of same element have different atomic weights.Ītoms of different elements are different in all respects.Ītoms of different elements are sometimes similar in some respects. Matter consists of small indivisible particles called atoms.Ītom is no longer indivisible, but consists of neutrons, protons and electrons.Ītoms of same element are alike in all respects.Īll atoms have isotopes. Let us see the contradictions of Dalton’s theory by the modern atomic theory. Hence Dalton’s theory does not give an explanation regarding further divisibility of atoms and also the internal structure of an atom. Role of atom in a chemical reaction: Atom is the smallest particle of matter that takes part in a chemical reaction.Ĭontradiction of Dalton’s atomic theory by modern atomic theoryįurther experiments conducted by scientists have provided the evidence that atoms are further divisible and made of fundamental particles called electrons, protons and neutrons. For example, the ratio of combination of hydrogen and oxygen to form water molecule ( H 2 O) is 2:1 which is a whole number ratio.Ħ. Combination of atoms: Atoms of different elements combine in a whole number ratio to form compounds. For example, atoms of hydrogen and oxygen elements are different in all respects.ĥ. Atoms of different elements are different. For example, atoms of hydrogen element are identical in all respects. Atoms of similar elements and dissimilar elements: Atoms of a given element are identical in all respects – same mass, same size and same properties. Invincibility of atoms: Atoms can be neither created nor destroyed in a chemical reaction.Ĥ. Indivisibility of atoms: Atoms are indivisible. Composition of matter: Matter is made of very small particles called atoms.Ģ. The main postulates of this theory are as follows:ġ. In 1803, an English Chemist, John Dalton, put forward his Atomic Theory. They gave the name atomos (in Greek, atomos means indivisible) to these ultimate particles. They thought that on dividing a piece of a substance, one would ultimately get a particle that could not be divided any further.

In the fifth century BC, the Greek philosophers Democritus and Leukiposs came up with a similar idea. (In Sanskrit, param means final or ultimate and anu means particle.) Kanad further said that two or more paramanus combine to form bigger particles. Matter is not continuous, and made up of tiny particles, named paramanus. Way back as the sixth century BC, the Indian philosopher Maharshi Kanad came forward with the following idea. Now, let us learn a little more about this idea that has brought about a revolution in science. In this chapter, we are going to explore atom and its constituents. Atoms and the study of atoms are a world unto themselves. They are the basis for everything in the Universe. In our earlier classes of chemical classification of matter, we have learnt that matter is made up of atoms and molecules.