The electrons revolve around the nucleus.The nucleus of an atom contains protons and neutrons.The energy of an electron is determined by the shell in which it is present.Īll the mass of an atom is concentrated in the nucleus. Electron in the extranuclear part revolve in the discrete orbits around the nucleus. Therefore the mass of an electron can be treated as negligible.
Mass of an electron is 1800 times less than that of a hydrogen atom. Each electron carries one unit of negative charge (-1e). Electron (e –): Electron is a negatively charged subatomic particle and is denoted by the symbol ‘e-’. The mass of a neutron is approximately lu, which is almost equal to that of a proton.ģ. The number of neutron in the nucleus is denoted by the symbol ‘N’ Atomic nuclei of all the elements except hydrogen with atomic mass lu, contain neutrons. Neutron (n): Neutron is an electrically neutral subatomic particle and is denoted by the symbol ‘n’. (1u = 1.66 × 10 -27g) (The mass of one hydrogen atom is also approximately lu.)Ģ. The mass of one proton is approximately lu (1 Dalton). When total positive charge on the nucleus is expressed in the unit ‘e’, its magnitude is equal to the number of proton in the nucleus. Each proton carries a positive charge of +1e. A proton is represented by the symbol ‘p’. The positive charge on the nucleus is due to the proton in it. Proton (p): Proton is a positively charged subatomic particle in the atomic nucleus. Protons and neutrons are the two types of nucleons or subatomic particles and electrons are subatomic particles in the extra nuclear part.ġ. The nucleus contains two types of subatomic particles together called nucleons. These contain three types of subatomic particles. What is meant by subatomic particle? Give brief information of three subatomic particles with reference to electrical charge, mass and location.Ī particle which is a constituent of an atom hence smaller than the atom is called subatomic particle.Īn atom is formed from the nucleus and the extranuclear part. Therefore, the atomic number and mass number of carbon are 6 and 12 respectively. the proton number of carbon is 6 and the mass number is total number of protons and neutrons in the carbon, i.e. The total number of protons and neutrons in the nucleus of the atom is called the atomic mass number. What is meant by atomic mass i number? Explain how the atomic number and mass number of carbon are 6 and 12 respectively.
It means that there is relationship between the valency of an element and the number of electrons in its valence shell. This number ‘one’ matches with the valency of hydrogen which is also one. The electronic configuration of hydrogen shows that there is one electron less than the complete duplet state. H 2, HCl) that valency of hydrogen is one. The molecules formed by combination with hydrogen (E.g.
It is confirmed that the valency is zero when electron octet (or duplet) is complete.Ītoms of all the elements except inert gases have tendency to combine with other atoms, i.e. Similarly argon contains eight electrons in the valence shell, i.e. The valence shell of neon is completely filled, i.e. Helium atom contains two electrons, indicates that the outermost shell of helium has an electron duplet. These elements are chemically inert, i.e. Helium and neon, atoms of both these gaseous element do not combine with any other atom. Valence electrons: The electrons in the outermost shell of an atom of an element are called valence electrons. Valency: The capacity of an element to combine with another element is known as valency. What is meant by valency of an element? What is the relationship between the number of valence electron and valency? The positive charge is in the nucleus of the atom. Atom is homogenous sphere of positive charge.Ģ. According to Rutherford’s atomic model the negatively charged electrons revolve around the nucleus.Ģ. According to Thomson’s atomic model, the negatively charged electrons are embedded in a gel of positive charge.ġ. What is the difference in the atomic models of Thomson and Rutherford?ġ. Maharashtra State Board Class 8 Science Solutions Chapter 5 Inside the AtomĬlass 8 Science Chapter 5 Inside the Atom Textbook Questions and Answers Balbharti Maharashtra State Board Class 8 Science Solutions Chapter 5 Inside the Atom Notes, Textbook Exercise Important Questions and Answers.
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