Q.Make the pairs:
'A': a. Neutrons b. p-orbital c. charge on electron d. Lyman series
'B': i. six electrons ii. -1.6×10⁻¹⁹ C iii. Ultraviolet region iv. Chadwick

An atom is built from three subatomic particles that matter to chemistry: the electron, the proton and the neutron. The proton and neutron sit together inside a tiny, dense central nucleus and are jointly called nucleons; the electron occupies the much larger extranuclear space around that nucleus. The electron (symbol e⁻) carries a charge of −1.6022×10⁻¹⁹ C (relative charge −1) and a mass of 9.10938×10⁻³¹ kg — about 1837 times lighter than a proton, so its mass is usually treated as negligible (≈0 u). The proton (symbol p) carries +1.6022×10⁻¹⁹ C (relative charge +1) and a mass close to 1 u (1.6726×10⁻²⁷ kg). The neutron (symbol n) carries no charge and has a mass, also close to 1 u, almost identical to the proton's. J. J. Thomson identified the electron in 1897 from cathode-ray tube experiments; Ernest Rutherford i …