Where is the mass of the atom concentrated?

Academic Chemistry NCERT Class 9

The mass of an atom is concentrated in its nucleus.

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Updated on: 14-Mar-2023

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In the α-scattering experiment, few α-particles rebounded because(a) Most of the space in the atom is occupied.(b) Positive charge of the atom occupies very little space.(c) The mass of the atom is concentrated in the centre.(d) all positive charge and mass of the atom is concentrated in small volume.
Mass of one atom of oxygen is
If one mole of carbon atom weighs 12g, what is the mass in grams of 1 atom of carbon?
Name the particles which actually determine the mass of an atom.
If bromine atom is available in the form of say, two isotopes 7935Br (49.7%) and 8135Br (50.3%), calculate the average atomic mass of bromine atom.
Fill in the blanks in the following statements :(a) The number of protons in the nucleus of an atom is called its ....................(b) The total number of protons and neutrons in the nucleus of an atom is called its ....................(c) An atom has atomic mass number 23 and atomic number 11. The atom has .................... electrons.(d) An atom of an element has 11 protons, 11 electrons and 12 neutrons. The atomic mass of the atom is ....................(e) If the nucleus of an atom has atomic number 17, mass number 37 and there are 17 electrons outside the nucleus, the number of neutrons in it is ....................(f) Almost all the mass of an atom is concentrated in a small region of space called the ....................(g) Cathode rays are a beam of fast-moving ....................(h) The anode rays obtained from hydrogen gas consist of particles called ....................(i) The maximum number of electrons that can be accommodated in L shell are ....................(j) The maximum number of electrons that can go into the M shell is ....................(k) The subatomic particle not present in a hydrogen atom is ....................(l) The electron has .................... charge, the proton has .................... charge, and the neutron has .................... charge.
Rutherford’s α–particle scattering experiment showed thatelectrons have a negative chargethe mass and positive charge of the atom is concentrated in the nucleusneutron exists in the nucleusmost of the space in the atom is empty Which of the above statements are correct?(a) (i) and (iii)(b) (ii) and (iv)(c) (i) and (iv)(d) (iii) and (iv)
(a) Name the element used as a standard for atomic mass scale.(b) Which particular atom of the above element is used for this purpose?(c) What value has been given to the mass of this reference atom?
The mass of one atom of an element X is 2.0 × 10–23 g.(i) Calculate the atomic mass of element X.(ii) What could element X be?
Calculate(a) the mass of one atom of oxygen(b) the mass of one molecule of oxygen(c) the mass of one mole of oxygen gas(d) the mass of one ion of oxygen(e) the number of atoms in 1 mole of oxygen molecule
If one mole of carbon atoms weighs 12 grams, what is the mass (in grams) of 1 atom of carbon?
Establish the relationship between atomic number, mass number, isotopes, isobars, and valency of an atom.
(a) Describe Bohr's model of the atom. How did Neils Bohr explain the stability of atom?(b) An element has an atomic number of 11 and its mass number is 23. What is the arrangement of electrons in the shells? State nuclear composition of an atom of the element.
Name the central part of an atom where protons and neutrons are held together.
Where are electrons placed in an atom?

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