Special Sub-Topic: Structure of an Atom
|The mass of an electron is 1.6 * 10^-19 kg.|
f. This is actually the charge of an electron. Its mass is 9.109 * 10^-31 kg.
|Atomic mass is expressed in ________________.|
atomic mass units (amu). It is very difficult to measure the exact weight of an atom and hence the weight of an atom is compared to that of a hydrogen anion. Hence, the weight of a neutron is 1 amu and that of an electron is 0.000544 amu. A proton weighs 0.9998 amu. Source: "Chemistry made easier" by Smith.
|Pick the true statement out of the following.|
Number of neutrons = mass number - atomic number.. The entire mass of an atom is concentrated in its nucleus and is due to the presence of protons and neutrons. Thus, atomic mass number is approximately same as atomic weight, as only the protons and neutrons contribute to the weight of an atom. Protons are approximately 1846 times heavier than an electron. Thus the mass number - the atomic number gives you the number of neutrons. For accurate measurements and analysis mass numbers are not rounded off to whole numbers. Source: "1001 questions on Atomic Number" by Chavhan.
|Rutherford's model of an electron was more accurate than Bohr's.|
f. According to Rutherford, electrons revolve around the positively charged nucleus in different orbits. According to the first law of thermodynamics, a charged body moving with such a high velocity should radiate energy and due to this continuous loss of energy the radius of the orbit of the electron should become smaller and the electron should fall in the nucleus. However this behaviour was not observed. He also stated that, due to this revolution of the electrons, a continuous atomic spectrum should be observed. However the atomic spectrum is not continuous but consists of lines of different wavelengths. These drawbacks were corrected by Bohr. Bohr stated that when electrons revolve in orbits, they neither radiate nor absorb any energy. Energy is only lost or gained if an electron shifts from one orbit to another. Thus Bohr's electronic theory was more accurate. Source: "Physical Chemistry" by Dr. R.K.Gupta.
|Einstein won the Nobel Prize for his equation E=mc^2, where E is the energy gained, m is the loss in mass and c is the speed of light.|
f. It is a very popular misconception that Einstein won the Nobel prize for this equation. It is quite true that this was a major step in nuclear physics and also helped in the production of the nuclear bomb, but Einstein won the Nobel Prize for Physics for his definition and work on a photon, which in layman's terms means energy emitted as light.
|An electron has __________ quantum numbers.|
4 & four. The four quantum numbers are principal, magnetic, azimuthal and spin. The principal quantum numbers indicates the main orbit in which the electron is present. The azimuthal quantum number indicates the shape of the orbital. The magnetic quantum number indicates the orientation of the orbit in space and spin quantum number the spin of the electron.
|What principle states " The orbitals of lower energy are filled first and then those of higher energy. "|
Aufbau. Hund proposed the rule of maximum multiplicity which states that electrons having parallel spins are filled first in all orbitals then followed by electrons having anti parallel spins. Heisenberg's uncertainty principle states that the simultaneous determination of position and momentum of an electron in any orbit is greater than Neil Bohr's constant. Pauli's exclusion principle states that no electron can have the same four quantum numbers. Aufbau is German for building and hence the principle.
|Half and full filled orbitals are more stable than others.|
t. This is due to increasing atomic symmetry and electron density, which helps make them more stable. The actual reason for this phenomenon is still not known.
|Principal quantum number is denoted by ________.|
n. The principal quantum number is denoted by the letter n. It can take all positive values. The azimuthal quantum number is denoted by l. It can take values from 0 to (n-1). The magnetic quantum number is denoted by m and takes values from positive l to negative l. The spin quantum number denoted by s can take the value of +1/2 or -1/2.
|Which orbital is spherical in shape?|
s. The p orbital is dumbbell shaped and the others are complicated three-dimensional. The s orbital is spherical in shape and is also non-directional. Source: "Systematic Chemistry" by T.H.Khan. Hope you have enjoyed my quiz!
Did you find these entries particularly interesting, or do you have comments / corrections to make? Let the author know!
Send the author a thank you or
Submit a correction