(a) Which has max. uncertainty regarding positin and why ? Electron, proton and neutron.
(b) Find the number of waves associated with a light radiation of time period 5 ns.

A negatively charged muon (mass 207 times the mass of an electron) is captured in a Bohr’s orbit of high principal quantum number (n). The atom thus formed is called mesic atom. The muon in high energy state cascades down to lower orbits by emitting photons. (a) The emitted photons are X rays. Why? (b) Find the atomic number (Z) of a mu-mesic atom in which the orbit with n = 1 will just touch the nuclear surface. Assume that the nucleus has equal number of protons and neutrons.

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 atoms 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.

A uniformly charged sphere has charge Q. An electron (charge – e, mass m) revolves around it in a circular orbit of radius r. (a) Write the total energy (i.e., sum of its kinetic energy and electrostatic potential energy in the field of the sphere) of the electron. (b) If the time period of revolution of the electron in circular orbit of radius r is T, then find the time period if the orbital radius is made 4r.

The mass number of a particular element which has equal number of protons and neutrons is 32. What is the electronic configuration of the atom and its stable ion ?

An atom of element E contains 3 protons, 3 electrons and 4 neutrons : (a) What is its atomic number ? (b) What is its mass number ? (c) Write the electronic configuration of the element E (d) State whether element E is a metal or non-metal. Why ? (e) What type of ion, cation of anion, will be formed by an atom of element E ? Why ? (f) Write the symbol of the ion formed by an atom of element E (g) What could element X be ?