ರಸಾಯನ ಶಾಸ್ತ್ರದ ಇತಿಹಾಸ :

ಈ ಜಗತ್ತು ಪಂಚಮಹಾಭೂತಗಳಿಂದ ಆಗಿದೆ ಎಂದರು ಹಿಂದಿನವರು. ಆಕಾಶ , ಅಗ್ನಿ , ವಾಯು , ಜಲ ಮತ್ತು ಮಣ್ಣು ; ಈ ಪಂಚಮಹಾಭೂತಗಳು .

ವಸ್ತು , ಶಕ್ತಿ , ಆಕಾಶ ಮತ್ತು ಕಾಲ ಎಂದು ಇಂದಿನವರು ವರ್ಗಿಕರಣ ಮಾಡಿದರು . ವಾಯು, ಜಲ, ಮತ್ತು ಮಣ್ಣನ್ನು ಒಟ್ಟಿಗೆ ದ್ರವ್ಯ ಎಂದರು . ದ್ರವ್ಯವು ಸ್ಥಳವನ್ನು ಆಕ್ರಮಿಸುತ್ತದೆ . ಅದಕ್ಕೆ ದ್ರವ್ಯರಾಶಿ ಇದೆ .

೧೬೬೧ರಲ್ಲಿ ರಾಬರ್ಟ ಬಾಯ್ಲ್  ಧಾತುವಿನ ಪರಿಕಲ್ಪನೆ ನಿರೂಪಿಸಿದ . ಆತನು ಆಮ್ಲ ಮತ್ತು ಪ್ರತ್ಯಾಮ್ಲಗಳ ವಿವರ ನೀಡಿದ.

ಈತನು ಗಾಳಿಯ ಗುಣಗಳು ಅಧ್ಯಯನ ಮಾಡಿ, ಒಂದು ನಿರ್ದಿಷ್ಟ ರಾಶಿಯ ಅನಿಲದ ಗಾತ್ರ, ಒತ್ತಡ, ಹಾಗೂ ಉಷ್ಣತೆಯ ಸಂಭಂದದ ನಿಯಮವನ್ನು ನಿರೂಪಿಸಿದನು. 

ಒಂದೇ ಪ್ರಕಾರದ ಮೂಲ ಕಣಗಳಿಂದ ಆದ ದ್ರವ್ಯವನ್ನು ಧಾತು ಅಥವಾ ಮೂಲವಸ್ತು ಎಂದರು. ಒಂದು ಧಾತುವಿನ ಅತಿಸಣ್ಣ ಕಣಕ್ಕೆ ಪರಮಾಣು ಎಂದರು. ಒಂದೇ ಪ್ರಕಾರದ ಪರಮಾಣುಗಳಿಂದ ಆದ ವಸ್ತುವೇ ಧಾತು.

೧೮ನೇಯ ಶತಮಾನದಲ್ಲಿ ಜಲಜನಕ , ಆಮ್ಲಜನಕ . ಮತ್ತು ಇಂಗಾಲದ ಡೈ ಅಕ್ಸಯಿಡ್ ಎನ್ನುವ ಅನಿಲಗಳ ಶೋಧ ಮತ್ತು ಅವುಗಳ ಗುಣಗಳ ಅಧ್ಯಯನ ನಡೆಯಿತು .

೧೭೫೪ರಲ್ಲಿ ಜೋಸೆಫ್ ಬ್ಲ್ಯಾಕ್ ಎನ್ನುವ ಉಪನ್ಯಾಸಕನು ಸುಣ್ಣದ ಕಲ್ಲನ್ನು ಕಾಯಿಸಿ ಅದರಿಂದ ಇಂಗಾಲದ ಡೈ ಅಕ್ಸಯಿಡ್ ಅನಿಲ ಹೊರಸೂಸುವುದನ್ನು ಗಮನಿಸಿದನು. ಈತನು ನೀರಿನ ಗುಪ್ತೋಷ್ಣವನ್ನು ವಿವರಿಸಿದನು.

೧೭೬೬ರಲ್ಲಿ ಹೆನ್ರಿ ಕೆವೆಂಡಿಷ್ ತನ್ನ ಪ್ರಯೋಗಶಾಲೆಯಲ್ಲಿ ಜಲಜನಕ ಅನಿಲವನ್ನು ಕಂಡುಹಿಡಿದನು. 

೧೭೭೪ರಲ್ಲಿ ಪ್ರೀಸ್ಟ್ಲೆ ಪಾದರಸದ ಆಕ್ಸಯಿಡ್  ಅದಿರು ಕಾಯಿಸಿ ಆಮ್ಲಜನಕ ಅನಿಲ ಕಂಡುಹಿಡಿದನು .

೧೭೭೮ರಲ್ಲಿ ಫ್ರಾನ್ಸ ದೇಶದ ಲಾವೋಷಿಯೆರ್ ಎನ್ನುವ ವಿಜ್ಞಾನಿ ದಹನ ಕ್ರಿಯೆಯನ್ನು ವಿವರಿಸಿದನು . ಈತನು ಆಮ್ಲಜನಕ ಒಂದು ಧಾತು ಎಂದು ವಿವರಿಸಿದನು . ನಿಸರ್ಗದಲ್ಲಿ ಸಹಜವಾಗಿ ಆಮ್ಲಜನಕವು ಅನಿಲ ರೂಪದಲ್ಲಿ ಇರುತ್ತದೆ. ಗಾಳಿಯಲ್ಲಿ ೨೧% ಆಮ್ಲಜನಕ ಇದೆ . ಇದು ಕ್ರಿಯಾಶೀಲವಾಗಿದ್ದು ಅನ್ಯ ಧಾತುಗಳೊಂದಿಗೆ ರಾಸಾಯನಿಕವಾಗಿ ವರ್ತಿಸಿ ಆಕ್ಸಯಿಡಗಳನ್ನು ಉಂಟುಮಾಡುತ್ತದೆ ಎಂದು ತೋರಿಸಿದನು. ಗಾಳಿಯಲ್ಲಿ ೭೮% ಸಾರಜನಕ ಅನಿಲ ಇದೆ. ಉಳಿದ ಭಾಗ ಜಡ ಅನಿಲಗಳದ್ದು. ನೀರಾವಿಯ ಪ್ರಮಾಣ ಸದಾ ಬದಲಾಗುತ್ತಇರುತ್ತದೆ.

೧೭೮೯ರಲ್ಲಿ ಲಾವೋಷಿಯರನು ಮೊದಲಬಾರಿಗೆ ಅಂದಿನವರೆಗೆ ತಿಳಿದಿರುವ ೨೩ ಧಾತುಗಳ ಪಟ್ಟಿ ಮಾಡಿದನು . ಈತನು ರಾಸಾಯನಿಕ ಬದಲಾವಣೆಯಲ್ಲಿ ಭಾಗವಹಿಸುವ ಧಾತುಗಳ ರಾಶಿ ಸಂರಕ್ಚೆಣೆಯ ನಿಯಮವನ್ನು ವಿವರಿಸಿದನು. ಈತನನ್ನು ರಸಾಯನ ಶಾಸ್ತ್ರದ ಪಿತಾಮಹ ಎಂದು ಪರಿಗಣಿಸಲಾಗುತ್ತದೆ.

೧೭೯೪ರ ಫ್ರೆಂಚ್ ಕ್ರಾಂತಿಯಲ್ಲಿ ವಿಜ್ಞಾನಿ ಲಾವೊಸಿರನು ಕೊಲೆಯಾದನು. 

೧೭೮೯ ರಲ್ಲಿ  ಪ್ರೌಸ್ಟ್  ಎನ್ನುವ  ವಿಜ್ಞಾನಿಯು  ಎರಡು ಧಾತುಗಳು ರಾಸಾಯನಿಕವಾಗಿ ಸಂಯೋಗ ಹೊಂದುವಾಗ ಅವು ಒಂದು ನಿರ್ದಿಷ್ಟ ರಾಶಿಯ ಅನುಪಾತದಲ್ಲಿ ಸೇರಿಕೊಳ್ಳುತ್ತವೆ  ಎಂದು ನಿರೂಪಿಸಿದರು.

೧೮೦೦ರಲ್ಲಿ ನೀರಿನಲ್ಲಿ ವಿದ್ಯುತ್ ಪ್ರವಾಹ ಹರಿಸಿ , ನೀರನ್ನು ವಿಭಜಿಸಿ ಆಮ್ಲಜನಕ ಮತ್ತು ಜಲಜನಕ ಅನಿಲಗಳಾಗಿ ವಿಂಗಡಿಸಿದರು . ಆದ್ದರಿಂದ ನೀರು ಮೂಲವಸ್ತು ಅಲ್ಲ ಬದಲಿಗೆ ಇದೊಂದು ಸಂಯುಕ್ತ ವಸ್ತು ಎಂದು ಖಚಿತವಾಯಿತು .

ಈ ಪ್ರಯೋಗದಲ್ಲಿ ಹೊರಸೂಸಿದ ಜಲಜನಕ ಮತ್ತು ಆಮ್ಲಜನಕ ಅನಿಲಗಳ ಗಾತ್ರದ ಅನುಪಾತ ೨:೧ ಇರುತ್ತದೆ. ಅಂದರೆ ಎರಡು ವಿಭಿನ್ನ ಅನಿಲಗಳು ಒಂದು ನಿರ್ದಿಷ್ಟ ಗಾತ್ರದ ಅನುಪಾತದಲ್ಲಿ ಸೇರಿ ಸಂಯುಕ್ತ ವಸ್ತು ರೂಪಗೊಳ್ಳುತ್ತದೆ ಎಂದು ಸಿದ್ದವಾಯಿತು. ಇದನ್ನು ಗೆ ಲುಸಾಕಾರ ನಿಯಮ ಎನ್ನುವರು.

ನೀರು ವಿಭಜಿಸುವ ರಾಸಾಯನಿಕ ಕ್ರಿಯೆಗೆ ಹೊರಗಿನಿಂದ ಶಕ್ತಿ ಒದಗಿಸಬೇಕಾಯಿತು. ಇದಕ್ಕೆ ವಿರುದ್ಧವಾಗಿ ಜಲಜನಕ ಮತ್ತು ಆಮ್ಲಜನಕ ಅನಿಲಗಳು ರಾಸಾಯನಿಕವಾಗಿ ಸೇರಿ, ನೀರು ಉಂಟಾಗುವ ಬದಲಾವಣೆಯಲ್ಲಿ ಶಕ್ತಿ ಹೊರಗೆ ಹಾಕಲಾಗುತ್ತದೆ. ಹೀಗೆ ಶಕ್ತಿಯನ್ನು ಪಡೆದುಕೊಳ್ಳುವ ಅಥವಾ ಶಕ್ತಿಯನ್ನು ಹೊರಚೆಲ್ಲುವ, ಎರಡು ಪ್ರಕಾರದ ರಾಸಾಯನಿಕ ಕ್ರಿಯೆಗಳಿರುತ್ತವೆ.

೧೮೦೩ರಲ್ಲಿ ಡಾಲ್ಟನ್ ಎನ್ನುವ ವಿಜ್ಞಾನಿ ಧಾತುವಿನ ಪರಮಾಣು ಸಿಧಾಂತವನ್ನು ಮಂಡಿಸಿದನು. ಧಾತುಗಳು ಪರಮಾಣುಗಳೆಂಬ ಒಡೆಯಲಾಗದ ಅತಿಸಣ್ಣ ಕಣಗಳಿಂದ ಆಗಿವೆ ಎಂದು ವಿವರಿಸಿದನು . ವಿವಿಧ ಧಾತುಗಳ ಪರಮಾಣುಗಳು ಭಿನ್ನ ಭಿನ್ನ ರಾಶಿಯನ್ನು ಹೊಂದಿರುವುದಾಗಿ ತಿಳಿಸಿದನು . ಈತನು ಮೊದಲಬಾರಿಗೆ ಧಾತುಗಳ ಸಾಪೇಕ್ಷ ಪರಮಾಣು ರಾಶಿಗಳ ಪಟ್ಟಿ ಮಾಡಿದನು .

೧೮೧೧ರಲ್ಲಿ ಅವಗಾಡ್ರೋ ಎನ್ನುವ ವಿಜ್ಞಾನಿ ಅನಿಲಗಳ ಅಣು ರೂಪದ ಕಣಗಳ ಮೇಲೆ ಪ್ರಯೋಗಗಳನ್ನು ಮಾಡಿ; ಸಮಾನ ಗಾತ್ರದ ಯಾವುದೇ ಅನಿಲಗಳು ಸಮಾನ ಪ್ರಮಾಣದ ಕಣಗಳು ಹೊಂದಿರುತ್ತವೆಂದು ಪ್ರತಿಪಾದಿಸಿದನು.

ಸಮಾನ ಗಾತ್ರದ ಜಲಜನಕ ಹಾಗು ಅಮ್ಲಜನಕ ಅನಿಲಗಳ ರಾಶಿಯು ೧:೧೬  ಅನುಪಾತದಲ್ಲಿ ಇರುತ್ತದೆ. ಜಲಜನಕದ ಪರಮಾಣುವಿನ ಸಾಪೇಕ್ಷೆರಾಶಿ ೧ ಆದರೆ ಆಮ್ಲಜನಕದ್ದು ೧೬ ಆಗುತ್ತದೆ. ನೀರಿನ ಅಣು ರಾಶಿ ೧೮ ಇರುತ್ತದೆ.  ೧೮ ಗ್ರಾಂ ನೀರನ್ನು ಒಂದು ಮೋಲ್ ನೀರು ಎನ್ನುವರು. ಒಂದು ಮೋಲ್ ನೀರಿನಲ್ಲಿ ೬.೦೨೨ x ೧೦ರ ಘಾತ ೨೩ ನೀರಿನ ಕಣಗಳಿವೆ. ಇದನ್ನು ಅವಗಾಡ್ರೋ ಸಂಖ್ಯೆ ಎಂದು ಸೂಚಿಸುವರು. 

೧೮೧೨ರಲ್ಲಿ ಹಂಫ್ರಿ ಡೇವಿ ಎನ್ನುವ ವಿಜ್ಞಾನಿಯು ಲವಣಗಳ ಮೇಲೆ ಪ್ರಬಲವಾದ ವಿದ್ಯುತ್ ಹರಿಸಿ, ರಾಸಾಯನಿಕ ಬದಲಾವಣೆ ಉಂಟುಮಾಡಿ, ಹೊಸ ಧಾತುಗಳ ಶೋಧ ಮಾಡಿದನು. ಈತನು ಪೊಟ್ಯಾಸಿಯಂ ಸೋಡಿಯಂ, ಕ್ಯಾಲ್ಸಿಯಂ ಮ್ಯಾಗ್ನೇಸಿಯಂ ಬೇರಿಯಂ ಮತ್ತು ಸ್ಟ್ರಾನಟಿಯಂ ಧಾತುಗಳನ್ನು ಕಂಡುಹಿಡಿದನು. ಅಲ್ಲದೆ ಕ್ಲೋರಿನ್ ಅನಿಲವೂ ಕೂಡಾ ಒಂದು ಧಾತು ಎಂದು ಸಿದ್ಧಮಾಡಿದ.

೧೮೨೬ ರಲ್ಲಿ ಡಾಲ್ಟನ್ನ ಶಿಷ್ಯನಾದ ಬರ್ಜೆಲಿಯಸನೂ, ಧಾತುಗಳನ್ನು ಹೆಸರಿಸಿದ  ಮತ್ತು ಅವುಗಳ ಹೆಸರಿನ ಮೂಲಾಕ್ಷರದಿಂದ ಧಾತುಗಳನ್ನು ಸಾಂಕೇತಿಕವಾಗಿ ಬರೆಯುವ ಕಲೆ ರೂಢಿಸಿದನು . ಇದರಿಂದ ಸಂಯುಕ್ತ ವಸ್ತುಗಳನ್ನು ಸಾಂಕೇತಿಕವಾಗಿ ಅಣು ಸೂತ್ರದ ರೂಪದಲ್ಲಿ ಬರೆಯಲು ಅನುಕೂಲವಾಯಿತು.

೧೮೨೮ರಲ್ಲಿ ವೋಹ್ಲರನು  ಮೊದಲಬಾರಿಗೆ ನಿರಯವ ರಾಸಾಯನಗಳನ್ನು ಬಳಸಿ, ಜೀವಿಗಳಲ್ಲಿ ಕಂಡುಬರುವ ಯೂರಿಯಾ ಎನ್ನುವ ಸಾವಯವ ಪದಾರ್ಥವನ್ನು ತಯ್ಯಾರಿಸಿದನು.

೧೮೩೦ರ ವರೆಗೆ ಕಂಡುಹಿಡಿದ ಧಾತುಗಳ ಸಂಖ್ಯೆ ೫೪ಕ್ಕೆ ಏರಿತು.

೧೮೩೪ರಲ್ಲಿ ಮೈಕಲ್ ಫ್ಯಾರಡೆಯವರ ನಿರೂಪಣೆ ; "ಅಯಾನಿಕ್ ದ್ರಾವಣಗಳಲ್ಲಿ ವಿದ್ಯುತ್ ಹರಿಸಿದಾಗ ಉಂಟಾಗುವ ರಾಸಾಯನಿಕ ಬದಲಾವಣೆಯು, ದ್ರಾವಣದಲ್ಲಿ ಹರಿಸಿದ ಒಟ್ಟು ವಿದ್ಯುತ್ತಿನ ಮೊತ್ತಕ್ಕೆ ಅನುರೂಪವಾಗಿ ಇರುತ್ತದೆ."

೧೮೪೧ರಲ್ಲಿ ಲಂಡನ್ ಪಟ್ಟಣದಲ್ಲಿ ರಾಸಾಯನ  ಶಾಸ್ತ್ರದ ಸಂಘ  ಸ್ಥಾಪನೆಗೊಂಡಿತು. 

೧೮೫೨ರಲ್ಲಿ ರಾಸಾಯನಿಕ ಸಂಯೋಗ ಸಾಮರ್ತ್ಯಯ ನಿರೂಪಣೆಯಾಯಿತು.

೧೮೫೯ರಲ್ಲಿ ಬನ್ಸೆನ್ ರೂ, ಪ್ರತಿಯೊಂದು ಧಾತುವು ತನ್ನದೇ ಆದ,  ವಿಶಿಷ್ಟ ಬೆಳಕಿನ ವರ್ಣಪಟಲವನ್ನು ಉಂಟುಮಾಡುತ್ತದೆ ಎಂದು ಕಂಡುಹಿಡಿದರು. ಈ ವಿಧಾನವು ಹೊಸ ಧಾತುಗಳನ್ನು ಕಾಡುಹಿಡಿಯಲು ಅನುಕೂಲವಾಯಿತು. 

೧೮೬೦ರಲ್ಲಿ ವಿಜ್ಞಾನಿ ಕೆಕೂಲೆಯವರ ನೇತ್ರಿತ್ವದಲ್ಲಿ , ಜರ್ಮನಿ ದೇಶದಲ್ಲಿ ಮೊದಲಬಾರಿಗೆ ಜಾಗತಿಕ ರಸಾಯನ ಶಾಸ್ತ್ರದ ಸಮ್ಮೇಳನ ಏರ್ಪಟ್ಟಿತ್ತು. ಇದರಲ್ಲಿ ೧೪೦ ಜನ ವಿಜ್ಞಾನಿಗಳು ಪಾಲ್ಗೊಂಡರು.

೧೮೬೯ರಲ್ಲಿ ಸೈಬೀರಿಯಾದ ವಿಜ್ಞಾನಿ ಮೆಂಡೆಲಿವರು ಧಾತುಗಳ ಆವರ್ತಕ ಕೋಷ್ಟಕವನ್ನು ಪ್ರಕಟಿಸಿದರು. ಅವರು ಅಲ್ಲಿಯವರೆಗೆ ತಿಳಿದಿರುವ ೬೬ ಧಾತುಗಳನ್ನು ಕೋಷ್ಟಕದಲ್ಲಿ ಅಡ್ಡಸಾಲು ಹಾಗು ಕಂಬಸಾಲುಗಳಾಗಿ ವರ್ಗಿಕರಿಸಿದರು. ಧಾತುಗಳನ್ನು ಅವುಗಳ ಪರಮಾಣು ರಾಶಿಯ ಏರಿಕೆಯ ಕ್ರಮದಲ್ಲಿ ಬರೆದರು. 

೧೮೮೭ರಲ್ಲಿ ಆಮ್ಲ, ಪ್ರತ್ಯಾಮ್ಲ, ಮತ್ತು ಲವಣಗಳು ನೀರಿನಲ್ಲಿ ಕರಗಿ ಅಯಾನ್ಗಳಾಗಿ ಬೇರ್ಪಡುತ್ತವೆ ಎಂದು ಕಂಡುಕೊಂಡರು.

೧೮೯೮ರಲ್ಲಿ ವಿಲಿಯಂ ರಾಮಸೇ  ಎನ್ನುವ ವಿಜ್ಞಾನಿ, ಜಡ ಅನಿಲಗಳನ್ನು ಕಂಡುಹಿಡಿದರು.

೧೯೦೦ರ ಹೊತ್ತಿಗೆ ಧಾತುಗಳ ಸಂಖ್ಯೆ ೮೮ಕ್ಕೆ ತಲುಪಿತು.

೧೮೯೭ರಲ್ಲಿ ಜೆ ಜೆ ಥಾಮ್ಸನ್ನರು ಕ್ಯಾಥೋಡ್ ಕಿರಣಗಳ ಪ್ರಯೋಗ ಮಾಡಿ, ಎಲ್ಲಾಧಾತುಗಳ ಪರಮಾಣುಗಳು  ಎಲೆಕ್ಟ್ರಾನ್ ಗಳೆಂಬ ಉಪಕಣಗಳು ಹೊಂದಿವೆ ಎಂದು ವಿವರಿಸಿದರು. ಎಲೆಕ್ಟ್ರಾನ್ ಗಳು ಋಣ ವಿದ್ಯುತ್ ಆವೇಶ ಹೊಂದಿರುತ್ತವೆ.

೧೯೧೧ರ ಹೊತ್ತಿಗೆ ಪರಮಾಣುವೂ ಋಣ ವಿದ್ಯುತ್ ಆವೇಶಯುಳ್ಳ ಎಲೆಕ್ಟ್ರಾನ್ ಮತ್ತು ಧನ ಆವೇಶಯುಳ್ಳ ಬೀಜಕೇಂದ್ರ ಹೊಂದಿದೆ ಎಂದು ರದರಫೋರ್ಡರ ಪ್ರಯೋಗಗಳಿಂದ ಖಚಿತವಾಯಿತು. ಮೂಲತಃ ಪರಮಾಣುವಿನ ರಾಶಿಯು ಬೀಜಕೇಂದ್ರದ್ದೇ ಆಗಿದೆ. ಎಲೆಕ್ಟ್ರಾನಿನ ರಾಶಿಯು ನಗಣ್ಯ .

೧೯೧೩ರಲ್ಲಿ ಡೆನ್ಮಾರ್ಕಿನ ವಿಜ್ಞಾನಿ ನೀಲ್ಸ ಬೊಹರರು, ಹೈಡ್ರೋಜನ್ ಪರಮಾಣುವಿನ ರಚನಾ ಸಿಧಾಂತವನ್ನು ಎಸೆಸ್ವಿಯಾಗಿ ವಿವರಿಸಿದರು. ಪರಮಾಣುವಿನ ಬೀಜಕೇಂದ್ರದ ಸುತ್ತ ಎಲೆಕ್ಟ್ರಾನ್ ನಿರ್ಧಾರಿತ ಶಕ್ತಿ ಕವಚದಲ್ಲಿ ಮಾತ್ರ ಸುತ್ತುತ್ತಿರುತ್ತದೆ. ಪರಮಾಣುವಿನ ಹೆಚ್ಚಿನ ಗಾತ್ರ ಎಲೆಕ್ಟ್ರಾನುಗಳೇ ಆಕ್ರಮಿಸಿಕೊಂಡಿರುತ್ತವೆ.

೧೯೧೪ರಲ್ಲಿ ಆಂಗ್ಲ ವಿಜ್ಞಾನಿ ಹೆನ್ರಿ ಮೊಸೆಲಿಯವರಿಂದ ಪರಮಾಣು ಸಂಖ್ಯೆಯ ವ್ಯಾಖ್ಯಾನ ನೀಡಲಾಯಿತು. ಪರಮಾಣು ಸಂಖ್ಯೆಯು ಪರಮಾಣು ಬೀಜ ಹೊಂದಿರುವ ಒಟ್ಟು ಪ್ರೋಟಾನ್ ಗಳ  ಸಂಖ್ಯೆಗೆ ಸಮ ಇರುತ್ತದೆ. ಇದಾದನಂತರ ಧಾತುಗಳ ಆವರ್ತಕ ಕೋಷ್ಟಕವನ್ನು ಧಾತುಗಳ ಪರಮಾಣು ಸಂಖ್ಯೆ ಬಳಸಿ ಕೋಷ್ಠಕದ ನ್ಯೂನತೆಗಳನ್ನು ತಿದ್ದಲಾಯಿತು. ಆಧುನಿಕ ಆವರ್ತಕ ಕೋಷ್ಟಕದಲ್ಲಿ ೧೮ ಕಂಭ ಸಾಲುಗಳಿವೆ.

೧೯೧೬ರಲ್ಲಿ ಜ್ಯೂಲಿಯಸರಿಂದ, ಅಯಾನಿಕ್ ಸಂಯುಕ್ತಗಳ ರಚನೆಯಲ್ಲಿ, ಪರಮಾಣುಗಳ  ಅಷ್ಟಕ ನಿಯಮ ನಿರೂಪಣೆ.

೧೯೧೬ರಲ್ಲಿ ಅಮೆರಿಕೆಯ ವಿಜ್ಞಾನಿ ಜಿ. ಎನ್. ಲೆವಿಸರು, ರಾಸಾಯನಿಕ ಸಹವೇಲೆನ್ಸಿ ಬಂಧದ ನಿರೂಪಣೆ ಕೊಟ್ಟರು. ಲೆವಿಸರು ಸಹವಾಲೆನ್ಸಿ ಬಂಧ ಬಳಸಿ, ಸಂಯುಕ್ತ ಕಣಗಳ ಅಣುರಚನೆಯನ್ನು ಎಸೆಸ್ವಿಯಾಗಿ ವಿವರಿಸಿದರು. 

ಅವರು, ೧೯೨೩ರಲ್ಲಿ ಲೆವಿಸ್ ಆಮ್ಲ ಮತ್ತು ಪ್ರತ್ಯಾಮ್ಲಗಳ ಪರಿಕಲ್ಪನೆ ಕೊಟ್ಟರು. ರಾಸಾಯನಿಕ ಬದಲಾವಣೆಯಲ್ಲಿ, ಲೆವಿಸ್ ಆಮ್ಲಗಳು, ಇಲೆಕ್ಟ್ರಾನ್ ಜೋಡಿಯನ್ನು [ಪ್ರತ್ಯಾಮ್ಲಗಳಿಂದ] ಸ್ವೀಕರಿಸುತ್ತವೆ.

೧೯೧೯ರಲ್ಲಿ ರದರ್ಫೋರ್ಡರು, ಪರಮಾಣು ಬೀಜಕೇಂದ್ರದಲ್ಲಿರುವ  ಧನಾವೇಶಯುಳ್ಳ ಪ್ರೋಟಾನ್ ಕಣವನ್ನು ಕಂಡುಹಿಡಿದರು.

೧೯೨೪ರಲ್ಲಿ ಬ್ರೊಗ್ಲೆಯವರಿಂದ ಎಲೆಕ್ಟ್ರಾನಿನ ರಚನಾ ರೂಪ, ಅಲೆ ಹಾಗೂ ಕಣ ಎನ್ನುವ ದ್ವಿಗುಣ ಪ್ರಕೃತಿಯ ನಿರೂಪಣೆ.

೧೯೨೬ರಲ್ಲಿ ಶ್ರೋಡಿಂಗರರಿಂದ ಪರಮಾಣುವಿನ ರಚನೆಯ ಶಕಲಸಿಧಾಂತದ ನಿರೂಪಣೆ.

೧೯೩೨ರಲ್ಲಿ ಜೇಮ್ಸ್ ಚಾಡ್ವಿಕ್ ರವರು, ಪರಮಾಣು ಬೀಜಕೇಂದ್ರ ಹೊಂದಿರುವ ನ್ಯೂಟ್ರಾನ್ ಎನ್ನುವ ಉಪಕಣವನ್ನು ಕಂಡುಹಿಡಿದರು. ಈ ಕಣಕ್ಕೆ ಯಾವುದೇ ವಿದ್ಯುತ್ ಆವೇಷ ಇಲ್ಲ. ಹೀಗೆ ಒಂದು ಪರಮಾಣುವೂ ಎಲೆಕ್ಟ್ರಾನ್, ಪ್ರೋಟಾನ್, ಮತ್ತು ನ್ಯೂಟ್ರಾನ್ ಎನ್ನುವ ಸೂಕ್ಷ್ಮ ಕಣಗಳಿಂದ ಆಗಿದೆ. ಪ್ರೋಟಾನ್ ಅಥವಾ ನ್ಯೂಟ್ರಾನ್ ಕಣದ ರಾಶಿಗೆ ಹೋಲಿಸಿದರೆ ಎಲೆಕ್ಟ್ರಾನ್ ರಾಶಿಯು ನಗಣ್ಯ ಎನಿಸುತ್ತದೆ. ಆದರೆ ಎಲೆಕ್ಟ್ರಾನ್ ಮತ್ತು ಪ್ರೋಟಾನ್ ಗಳ ವಿದ್ಯುತ್ ಆವೇಶವು ಸಮ ಇರುತ್ತದೆ.  ಒಂದು ಪರಮಾಣುವಿನ ಎಲೆಕ್ಟ್ರಾನ್ ಮತ್ತು ಪ್ರೋಟಾನ್ ಗಳ ಸಂಖ್ಯೆ ಸಮಾನವಾಗಿರುತ್ತದೆ.

 Hindu Calendar

 Throughout most of history, most calendars were based on the moon and each waxing and waning of the moon would count as one month. One example of this is the Muslim Hijri calendar, which takes 12 lunar months. However, 12 lunar months are only 354 days, which is 11 days shorter than a solar year. This creates a problem because if people use a purely lunar calendar, the months in which spring, summer or winter occur will change from year to year (as the seasons depend on the earth’s movement around the sun). In fact, every few years, summer would occur in December!

The Hindu calendar is known as a lunisolar calendar. The 12 months move according to the moon and the year is 354 days long. However, every third year, 33 days (11 extra days * 3) are added by creating one extra lunar month of 29 days. The remaining four days are adjusted here and there.

The 12 Indian months are: Chaitra, Vaisakha, Jyeshtha, Ashadha, Shravana, Bhadra, Ashvin, Kartik, Agahana, Pausha, Magha, Phalguna. So every three years, one of these months occurs twice in the same year…it’s like having two Marches or two Julys in a year!

 There are two main calendars in common use in India today, the Vikram Samvat with a zero point of 57 BC and the Shaka Samvat with a zero point of 78 AD. They are used for calculating the dates of all Hindu festivals like Diwali and Holi.

 Hindu calendar, dating system used in India from about 1000 BCE and still used to establish dates of the Hindu religious year. It is based on a year of 12 lunar months; i.e., 12 full cycles of phases of the Moon. The discrepancy between the lunar year of about 354 days and the solar year of about 365 days is partially resolved by intercalation of an extra month every 30 months.

 The Saka Calender is based on luni-solar reckoning of time. The calendar consists of 365 days and 12 months like the normal Gregorian calendar. Chaitra is the first month of the year beginning on March 22 which is the day after the Spring Equinox. During leap years, the starting day of Chaitra corresponds with March 21. To convert years in AD to Saka years, 78 must be subtracted for a date.

 The names of the months in Saka Calendar are: 

•    Chhaitra (March 21 – April 20)

•    Vaishakha (April 21-May 21)

•    Jyeshtha (May 22-June 21)

•    Ashadha (June 22- July 22)

•    Shravana (July 23-August 22)

•    Bhaadra (August 22-September 22)

•    Ashwin (September 23-October 22)

•    Kartika (October 23-November 21)

•    Agrahayana (November 22-December 21)

•    Pausha (December 22-January 20)

•    Magha (January 21- February 19) and 

•    Phalguna (February 20-March 20/21)

The month of Chaitra has generally 30 days but there are 31 days during leap years. The months of Vaish?kha, Jy?shtha, ?sh?dha, Shr?vana, Bhaadra, have 31 days while the rest have 30 days. This is done by taking into account the ellipticity of earth’s orbit around the sun.

 

Computation and calculation of time was a hallmark of all ancient civilizations. Egyptian and Mesopotamian civilization had their abiding interest in chronology and astronomy. The oldest and the largest civilization, the Indus valley civilization, was by far the most advanced and sophisticated in terms of chronological and astronomical acumen. They even had professional astronomers, called ‘nakshatra darshaks’ or ‘star gazers’, who meticulously observed and recorded the phases of the moon in reference to fixed constellations of stars. This method of calculation and its precision, sharply distinguishes Indian astronomy from the astronomy of all other countries.

The Indian calendar is ingeniously based on both the sun as well as the moon. It uses a solar year, but divides it into 12 lunar months. A lunar month, is the time required for the moon to orbit once around the earth and pass through its complete cycle of phases. Furthermore, these months are formulated in accordance with the successive entrances of the sun into the 12 rashis or the signs of the zodiac derived from the 12 constellations marking the path of the sun.

  Vedic literature show that the knowledge of chronology (science of Time) and chronometry (scientific measurement of Time) existed even during Vedic times, thousands of years before the Christian era. Knowledge of planetary motions, constellations, eclipses, solstices, seasons, etc. has existed since the beginning of the Vedic age. A method of distributing time into various periods such as days, fortnights, months and years was adopted for the purposes of civic life, these divisions being intimately connected with the affairs of the people. And because of the very fact that the Indian calendar was devised to serve the affairs of day-to-day living, it was allowed the freedom of being both lunar and solar. The Rig Veda, cites months being lunar, but years luni-solar. 

 This means that there was a constant correlation between the solar year and its monthly lunar divisions. A lunar month is precisely 29 days 12 hours 44 minutes and 3 seconds long. Twelve such months constitute a lunar year of 354 days 8 hours 48 minutes and 36 seconds. To help the lunar months coincide with the solar year, the practice arose of inserting intercalary (extra) months. In general, 60 solar months = 62 lunar months. And so an extra month, called the Adhik Maas (extra month), is inserted every 30 months, approximately every 2½ years. Such a practice was prevalent even in Vedic times. An intercalary month mentioned in the Rig Veda {Vedamãso dhrutavrato dvãdasha prajãvatah; vedã ya upajãyate. (I/25:8)} proves that the month was added to preserve the correspondence between a whole solar year and the 12 lunations.

Seasons within the Hindu calendar 

It is even more interesting, how the solar year was classified on the basis of seasons. The 12 lunar months of a solar year are divided into six ritus (seasons), each comprising of approximately two months. Since the seasons are solar based, each of the six seasons — Sharad (late monsoon), Hemant (early winter), Shishir (winter), Vasant (spring), Grishma (summer) and Varsha (monsoon)- commence around the 21st date (±2) of each even month of the Western calendar.

 The Hindu calendar recognizes the importance of the summer solstice and winter solstice in a solar year, determining the six seasons. The Dakshinayana or the sun’s southern course starts from June 21 till December 21, during which the day-length is successively getting shorter until it is the shortest in december. The Uttarayana or the sun’s northern course progresses from December 21 until June 21, during which the day-length gets successively longer until it is the longest in June. Sun reaches the equinox twice in a year, during which the length of day and night are equal. The first point is Vernal Equinox in March 20(Vasant Sampaat). The other point is called Autumnal Equinox in September 22(Sharad Sampaat).

 

Ancient India

About three lakh years ago, homosepians appeared in African plains.

200000 BCE- Probable birth of Humans evolved on the planet Earth. Monkey to man.

80,000 BCE- Humans appeared in this part of the earth, Jumbo Dveepa [Indin sub-continent].

74000 years ago, a volcanic eruption in Indonesia, destroyed life in the central and southern regions of India. Very few survived this carbon smoke eruption.

14,500 BCE- Brahma lived in India, Birth of Manu.

14500-11500 BCE Proto Indic language developed.

13500 BCE- The sage Viswamitra’s period.

11500- 3000 BCE Early Brahmi script evolved.

11200 BCE- Enormous earthquake in Kashmir Lake and flooding in the western part of India.

10000 BCE- The star, Agastya was visible at the south pole from Kanyakumari, the southern tip of India.

11200 BCE -10200 BCE- Rigveda was written during this time span.

9000 BCE- Atharvana Veda was written during this period.

7000- 3000 BCE Indus script was developed.

6778 BCE- Surya Siddhanta was written by Mayasura.

6777-5577 - Tretayuga period [1200 years].

5677-5577 BCE- The period of Ramayana.

5674 BCE- Birth of Shri Rama.[3rd February 5674 BCE]

5635 BCE- Ravana was killed by Rama.[in a war].

5577- 3177 BCE- Dwapara yuga. [2400 years].

3162 BCE- The period of Mahabharatha.

3102 BCE- Start of Kaliyuga time.

18th February 3192 BCE- Start of Kaliyuga.

2982 BCE- SaamaVeda and Yajurveda were written.

2000-1900 BCE- River Saraswathi dried up. There was a widespread drought all over the Indian subcontinent. And migration started to the outside world from India.

3000-2500 BCE- Indus Script refinement.

2500-1300 BCE- Ashokan or Mauryan Brahmi scipt.

2000- 0 BCE-Dialects of local languages were developed.

1864 BCE- Budha attained Nirvana.

1662 BCE-Mahapadma Nanda’s period.

1596- 1459- Mauryas period.

1500 BCE-Brahmi script evolved.

1400 BCE- six Vedangas were written.

1250BCE - 600 CE-Kushana Brahmi.

1200 BCE- Vedanga Jotisha

 

0719 BCE- Karttikadi Vikrama Era.

0057 CE- Chitradi Vikram Era.

 

0700BCE- Surya Siddhantha was re-written.

 

583 BCE- Saka Era

78 CE -Sakanta Era

 

0509 BCE- Adi Shankaracharya’s period. 

[Indian textbook errors-1380 years].

 

540 BCE-Tamil Brahmi script evolved in Palani.

0600 BCE- Kanaadha’s theory of matter[Atom].

0570-495 BCE- Pythagoras time. His Indian connection.

0300-400CE Devanagari Script evolved.

499 ACE- Aryabhata-I. A great mathematician and scientist.

598 ACE- Brahmagupta.

600 ACE- Bhaskara-I

950 ACE-Aryabhata-II

 

Indian time scale:

8000 years- Satya yuga [from 14500 to 6777 BCE] Vedic period.

1200 years -Treta yuga [6777 to 5577 BCE]

2400 years- Dwapara yuga [5577 to 3102 BCE]

Astronomy

Precession duration: 25700 years cycle.

       Invention of Telephone

On March 10, 1876, in Boston, Massachusetts, Alexander Graham Bell invented the telephone. 

Oersted discovered that an electric current creates a magnetic field. But could a magnetic field create electricity? If so, a new source of power beckoned. And the principle of electromagnetism, if fully understood and applied, promised a new era of communication.

In 1821 Michael Faraday reversed Oersted's experiment. He got a weak current to flow in a wire revolving around a permanent magnet. In other words, a magnetic field caused or induced an electric current to flow in a nearby wire. In so doing, Faraday had built the world's first electric generator.

In 1830 the great American scientist Professor Joseph Henry transmitted the first practical electrical signal. Henry created the forerunner of the telegraph. In the demonstration, Henry first built an electromagnet by winding an iron bar with several feet of wire. A pivot-mounted steel bar sat next to the magnet. A bell, in turn, stood next to the bar. From the electromagnet, Henry strung a mile of wire around the inside of the classroom. He completed the circuit by connecting the ends of the wires to a battery. Guess what happened? The steel bar swung toward the magnet, of course, striking the bell at the same time. Breaking the connection released the bar and it was free to strike again.

In 1837 Samuel Morse invented the first workable telegraph, applied for its patent in 1838, and was finally granted it in 1848. . A quick key tap broke the circuit momentarily, transmitting a short pulse to a distant sounder, interpreted by an operator as a dot. A more lengthy break produced a dash.

Yet as the telegraph was perfected, man's thoughts turned to speech over a wire.

On June 2, 1875, Bell and Watson were testing the harmonic telegraph when Bell heard a sound come through the receiver. Instead of transmitting a pulse, which it had refused to do in any case, the telegraph passed on the sound of Watson plucking a tuned spring, one of many set at different pitches. How could that be? Their telegraph, like all others, turned current on and off. But in this instance, a contact screw was set too tightly, allowing current to run continuously, the essential element needed to transmit speech. Bell realized what happened and had Watson build a telephone the next day based on this discovery. 

The Watson-built telephone looked odd and acted strangely. Bellowing into the funnel caused a small disk or diaphragm at the bottom to move. This disk was, in turn, attached to a wire floating in an acid-filled metal cup. A wire attached to the cup, in turn, led to a distant receiver. As the wire moved up and down it changed the resistance within the liquid. This now varying current was then sent to the receiver, causing its membrane to vibrate and thereby produce sound. This telephone wasn't quite practical; it got speech across, but badly. This transmitter was quickly dropped in favor of voice-powered or induced models. This transmitted speech on the weak electro-magnetic force that the transmitter and receiver's permanent magnets produced.

 

Finally, on March 10, 1876, one week after his patent was allowed, Bell succeeded in transmitting speech. He was not yet 30. Bell soon improved it by using an electromagnetic transmitter, a metal diaphragm, and a permanent magnet. The telephone had been invented.

       

 

 

 

 

 

 

 

 

      

 

 

 

 

 

 

 

 

  

The human voice on wires

 Simply using two insulated iron wires overhead along the streets, a human voice could be transmitted as an electrical signal generated by a telephone apparatus. If all such wires are terminated on a board, the board operator[also called telephone operator] could manually interconnect these lines as required by a service user at any time. This constitutes the simple theory of a telephone exchange. If the power supply needed to run the system is supplied from the central office itself, it was called central battery exchange. Such a service evolved in the USA long back after 1876 in Bell's lab.

This networked system made things easy to communicate immediately in a local area between business offices and homes as needed. The distance of telephone lines could be increased to talk with nearby villages by erecting lines of thick weld-copper conducting materials to reduce the electric resistance. 

For a local area, about five kilometers radius was standardized; beyond that distance, the voice would be very feeble to hear. A fifty volts DC battery supply was used to run the system. One such system was installed in Calcutta during British rule in India with less than 20 lines to start with. The system was gradually expanded to other presidencies like Bombay and Madras.

Over the time, some new innovations were made and the facilities were expanded to many princely states of India. Many such CBNM and CBM systems flourished all over India before Independence.

To interconnect the switching centers, trunk lines were constructed.

At the time of Indian independence, when all princely states were integrated into a single Nation as India, a department was created, called Post and Telegraph.

In 1950 the number of telephone exchanges absorbed from princely states was 196. The installed capacity of these 196 exchanges was 13,362 lines with 11,296 working connections.

After the next two decades, when electronic diodes and transistors were made available, for the first time, the voice modulators and demodulators were manufactured and used successfully to carry more than one telephone speech over the same pair of wires, between the neighboring towns and cities. These were called speech channels.

A standard three-channel system was evolved to make it possible to run four-voice signals together on a single pair of wires [called NCJ lines]. Later, the channel capacity was increased to eight channels on C-8 trunk lines. During the 1970s, One such system was working between Pune and Hyderabad which was constructed along national highway number nine in India. Repeater stations were installed in order to increase the power loss due to transmission lines. These stations were also used to drop or inject a channel at the local exchange office. This served to branch the transmission system as needed.

The business community and the government offices were the first users of this system. Indian railways used telecom services to control the movement of trains on railroads.

Gradually almost all the district places and important towns got telephone services in India.

 

Automatic local exchanges were developed using electromagnetic relay logic systems. One 200 lines switch needed one large room to house all accessories like the battery and power plant. It would take six months to install and commission one such system. The two motion selectors were used to connect the desired number as per dialed information. 50-lines switches were used for smaller towns. The 1980s saw this development in India. After 1980, the efficiency of the telephone service gradually increased because of PVC insulated u/g cables. The switching capacity expansions started regularly to increase the services to rural areas too. Gradually, the villagers started using the telephone facility. The Government thought that there should be at least one telephone in each village for communication. Many public call offices were opened. The DOT was separated from Postal services.

The 1990s saw the line of sight communication technology to carry bulk channels using microwave transmission systems. These systems inter-connected many metros together, in the length and breadth of India. A large number of channels capacity was used to extend STD [subscriber trunk dialing] facility to important customers. STD PCOs became a good source of revenue generation for DOT.

As a final information carrier system, OFC [Optical fiber cable] transmission systems were standardized for trunk working. Electronic exchange switches were manufactured using C-DOT technology in India. This became the tool for quick expansion of switching systems in order to provide on-demand new connections in most of the urban centers. The public demand also increased to own a telephone in most households. 

The local cable and overhead lines were a weak point in the telecom system and subjected to recurring fault due to rusting of the copper conductor in the wet atmosphere, and frequent interruption became a point of concern for telephone service users.

 

Some milestones in Indian Telephone systems:

In August 1907, the Central Battery working of telephones was first introduced in Kanpur.

1913-14 First automatic exchange was installed at Simla with a capacity of 700 lines with 400 actual connections.

1925-26, Conversion of Delhi Manual system to Auto System. 

1950-55, Step by Step strowger exchanges commissioned.

In 1953, 12 channel carrier systems introduced.

July 1959, First Coaxial route between Delhi-Agra commissioned.

December 1965, the First microwave route between Calcutta-Asansol opened.

1979, First optic fiber system, for local junction working, commissioned at Pune.

1984, C-DOT was established for indigenous development and production of digital exchanges.

1987-88, Large Scale introduction of Push Button telephone instruments.

 

By the 2000s, mobile telephony evolved, where the local cable was eliminated and microwave signaling was used to establish a connection for a phone call set-up. The mobile handset would provide the battery needed to speak. Later, smartphone handsets were made to extend internet services directly to mobile phones. e-mail and other messaging services stated. Gradually all open wire systems like trunk lines were eliminated, all over the country.