The atomic number (Z) represents the number of protons in the nucleus, which equals the number of electrons in a neutral atom. In Lithium’s case, with Z = 3, it has 3 protons and 3 electrons.
If Z = 3, what would be the valency of the element? Also, name the element. Read More »
The sample of element X is composed of 90% 168X and 10% 188X isotopes.
If bromine atom is available in the form of two isotopes 79 35Br (49.7%) and 81 35Br (50.3%), calculate the average atomic mass of bromine atom. Thus, the average atomic mass of bromine is 80u.
Electrons fill the lowest energy levels or shells first before occupying higher energy levels.
The maximum number of electrons in a shell is given by the formula 2n², where ‘n’ is the principal quantum number of that shell.
The electron distribution for the first eighteen elements follows the pattern: 2, 8, 8 for the first, second, and third energy levels (or shells) respectively.
Dalton’s model proposed that atoms were indivisible and identical spheres.
Thomson’s model, also known as the “plum pudding” model or the “raisin bun” model, proposed that atoms consist of a positively charged sphere with negatively charged electrons embedded within it, much like raisins in a pudding or plums in a bun.
Rutherford’s model arose from the famous gold foil experiment.
Bohr’s model built upon Rutherford’s nuclear model but introduced the concept of quantized electron orbits.
Compare all the proposed models of an atom given in this chapter. Read More »
Electron orbits: It didn’t specify how electrons moved around the nucleus. Classical physics predicted they would lose energy and spiral into the nucleus.
Light emission: It couldn’t explain how atoms emit specific frequencies of light.
What are the limitations of Rutherford’s model of the atom? Read More »
â–ş It couldn’t explain how negatively charged electrons were held within a positively charged sphere. According to electrostatics, they should repel each other.
â–ş It didn’t explain about the positively charged nucleus in the center of the atom.
â–ş The model couldn’t explain the results of Ernest Rutherford’s gold foil experiment, where some alpha particles deflected significantly, indicating a very small, dense core
What are the limitations of J.J. Thomson’s model of the atom? Read More »
Property Electron Proton Neutron Charge Negative (-1) Positive (+1) No charge (neutral) Mass Very small (9.1 x 10^-31 kg) Relatively heavy (1.67 x 10^-27 kg) Similar to proton (1.67 x 10^-27 kg) Location in Atom Outside the nucleus, in orbitals Inside the nucleus Inside the nucleus More Exercises Questions 2. What are the limitations of J.J. Thomson’s model
Compare the properties of electrons, protons and neutrons. Read More »
For electronic configuration, we only need to consider the electrons, which are not affected by the number of neutrons (isotopes) or the same mass number (isobars).
Write the electronic configuration of any one pair of isotopes and isobars. Read More »
Subatomic Particles in H, D, and T
Symbol Protons Neutrons Electrons
H 1 0 1
D (Deuterium) 1 1 1
T (Tritium) 1 2 1
For the symbol H, D and T tabulate three sub-atomic particles found in each of them. Read More »
Oxygen (O) has an atomic number of 8 and usually has 8 neutrons in its nucleus, so its most common isotope has a mass number of 16 (8 protons + 8 neutrons).
Sulphur (S) has an atomic number of 16. Its most common isotope has 16 neutrons, giving it a mass number of 32 (16 protons + 16 neutrons).
Find out the mass number of oxygen and sulphur atom Read More »
If the number of electrons in an atom is 8 and the number of protons is also 8
