Question
Which group of elements could be placed in Mendeleev’s periodic table later on, without disturbing the original order? Give reason.
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| Rules/Act | Year |
| (1) Sound Pollution (Control and Prevention) Rule | (a) 1980 |
| (2) Biomedical Waste (Management and Handling) Rule | (b) 2011 |
| (c) 1998 | |
| (d) 2000 |
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of $-CH_2-$ units | Boiling point $^\circ C$ |
| Ethene | $C_2H_4$ | $CH_2= CH_2$ | $2$ | $0$ | $-102$ |
| Propene | $C_3H_6$ | $CH_3–CH = CH_2$ | $3$ | $1$ | $-48$ |
| $1-$Butene | $C_4H_8$ | $CH_3–CH_2–CH = CH_2$ | ______ | ______ | $-6.5$ |
| $1-$Pentene | $C_5H_{10}$ | $CH_3–CH_2–CH_2–CH = CH_2$ | ______ | ______ | $30$ |