Define quantum numbers.

Give reasons for the following: Chlorine (atomic number 17) is more electronegative than:sulphur (atomic number 16).

Define the terms nucleus, nucleons, atomic number, mass number, isotopes, isobars, isotones.

Atom A has a mass number 209 and atomic number 82. Atom B has a mass number 209 and atomic number 83. (i) How many protons atom A has ?

Atom A has a mass number 209 and atomic number 82. Atom B has a mass number 209 and atomic number 83. (ii) How many protons atom B has ?

Atom A has a mass number 209 and atomic number 82. Atom B has a mass number 209 and atomic number 83. (iii) Are atoms A and B isotopes of the same element ?

If number of electrons in an atom is 8 and number of protons is also 8 , then (i) What is the atomic number of the atom ? , and (ii) what is the charge on the atom ?

What is the number of valence electrons in the atoms of an element having atomic number 13 ? Name the valence shell of this atom.