| 1 | A | B | C | D | E |
| --- | --- | --- | --- | --- | --- |
| 2 | Rutherfordium - Isotopes |  |  |  |  |
| 3 | Isotope | Half-life | Decay mode | Discovery year | Reaction |
| 4 | 253Rf | 48 μs | α, SF | 1994 | 204Pb(50Ti,n) |
| 5 | 254Rf | 23 μs | SF | 1994 | 206Pb(50Ti,2n) |
| 6 | 255Rf | 2.3 s | ε?, α, SF | 1974 | 207Pb(50Ti,2n) |
| 7 | 256Rf | 6.4 ms | α, SF | 1974 | 208Pb(50Ti,2n) |
| 8 | 257Rf | 4.7 s | ε, α, SF | 1969 | 249Cf(12C,4n) |
| 9 | 257mRf | 4.1 s | ε, α, SF | 1969 | 249Cf(12C,4n) |
| 10 | 258Rf | 14.7 ms | α, SF | 1969 | 249Cf(13C,4n) |
| 11 | 259Rf | 3.2 s | α, SF | 1969 | 249Cf(13C,3n) |
| 12 | 259mRf | 2.5 s | ε | 1969 | 249Cf(13C,3n) |
| 13 | 260Rf | 21 ms | α, SF | 1969 | 248Cm(16O,4n) |
| 14 | 261Rf | 78 s | α, SF | 1970 | 248Cm(18O,5n) |
| 15 | 261mRf | 4 s | ε, α, SF | 2001 | 244Pu(22Ne,5n) |
| 16 | 262Rf | 2.3 s | α, SF | 1996 | 244Pu(22Ne,4n) |
| 17 | 263Rf | 15 min | α, SF | 1999 | 263Db( e−, ν e) |
| 18 | 263mRf ? | 8 s | α, SF | 1999 | 263Db( e−, ν e) |
| 19 | 265Rf | 1.1 min | SF | 2010 | 269Sg(—,α) |
| 20 | 266Rf | 23 s? | SF | 2007? | 266Db( e−, ν e)? |
| 21 | 267Rf | 1.3 h | SF | 2004 | 271Sg(—,α) |
| 22 | 268Rf | 1.4 s? | SF | 2004? | 268Db( e−, ν e)? |
| 23 | 270Rf | 20 ms? | SF | 2010? | 270Db( e−, ν e)? |

Question: Which isotope has been reported?
Answer: Sixteen different isotopes have been reported with atomic masses from 253 to 270 (with the exceptions of 264 and 269).