# Atomic structure

 1. Which of the following is the standard for atomic mass? A. O-16 B. N-14 C. C-12 D. H-1 Option “C” is correct.An atomic mass unit (symbolized amu) is defined as precisely 1/12 the mass of an atom of carbon-12. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus.
 2. Positron is : A. electron with positive charge B. a nucleus with one neutron and one proton C. a nucleus with two protons D. a helium nucleus Option “A” is correct.The positron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of ½, and has the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two or more gamma ray photonsPositrons may be generated by positron emission radioactive decay or by pair production from a sufficiently energetic photon which is interacting with an atom in a material.
 3. The mass number of a nucleus is: A. is always less than its atomic number B. is always greater than its atomic number C. is always equal to its atomic number D. sometimes more than and sometimes equal to its atomic number Option “D” is correct.The mass number (A), is the total number of protons and neutrons ns) in an atomic nucleus so sometimes more than and sometimes equal to its atomic number, depends upon no of neutrons.
 4. Who among the following propounded the atomic theory? A. Benjamin Franklin B. Madame Curie C. Albert Einstein D. John Dalton Option “D” is correct.The modern atomic theory, which has undergone continuous refinement, began to flourish at the beginning of the 19th century with the work of the English chemist John Dalton.
 5. The correct relation between energy (E), momentum (P) and velocity (c) of proton is – A. p =EC² B. p = BC C. p = C/E D. p = E/C Option “D” is correct. The energy of a photon in vacuum is equal to E=pc (where p is the momentum of the photon, and c is the speed of light in vacuum)
 6. All the four quantum number can never be same for any two electrons. A. Heisenberg Uncertainty principle B. Pauli Exclusion Principle C. Schrodinger Wave Equation D. Bohr model of the hydrogen atom Option “B” is correct.The Pauli exclusion principle is the quantum mechanical principle that states that two identical fermions (particles with half-integer spin) cannot occupy the same quantum state simultaneously. In the case of electrons, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers
 7. Regarding the atom of a chemical element, the magnetic quantum number refers to ________. A. orientation B. shape C. size D. spin Option “A” is correct.
 8. Which quantum number defines the orientation of orbital in the space around the nucleus ? A. Principal quantum number (n) B. Angular momentum quantum number C. Magnetic quantum number D. Spin quantum number Option “C” is correct.Magnetic Quantum Number (m) : Gives the orientation of the orbital in space; in other words, the value of m describes whether an orbital lies along the x-, y-, or z-axis on a three-dimensional graph, with the nucleus of the atom at the origin. m can take on any value from −l to l.
 9. Which of the following determine the Chemical property of an element? A. number of protons B. number of electrons C. number of neutrons D. All of the above Option “B” is correct.?The Physical properties of an atom are determined by the number of Protons and Neutrons in the nucleus.The exchange of electrons takes place during the reaction of any particular element with another element. The number of electrons attributes to the Chemical property of an Atom.The number of protons and electrons are equal in number in the nucleus.
 10. How many electrons can remain in the outermost orbit of an atom? A. 2 B. 8 C. 18 D. no fixed limit Option “B” is correct.the maximum number of electrons that can be accommodated in the outermost orbit is – 8.The outermost shell in an atom cannot have more than eight electrons even if it has a capacity to take up more electrons. This is also called the octet rule