16. In an atomic nucleus, neutrons and protons are held together by
A. gravitational forces
B. exchange forces
C. coulombic forces
D. magnetic forces
17. ‘No two electrons in an atom can have the same set of four quantum numbers’ is
A. Newton’s law
B. Bohr’s law
C. Aufbau principle
D. Pauli’s exclusion principle
18. According to Avogadro’s Hypothesis, the smallest particle of an element or a compound, that can exist independently, is called ____ .
A. a molecule
B. a cation
C. an anion
D. an atom
19. Atoms of an element differ from those of all other elements in
A. atomic number and electronic configuration
B. number of neutrons and number of valence electrons
C. atomic number and number of valence electrons
D. number of neutrons and electronic configuration
20. Nuclear fission is caused by the impact of
A. neutron
B. proton
C. deuteron
D. electron