| 100% | ISOTOPE | 7 | One of two or more atoms with the same atomic number that contain different numbers of neutrons |
| 51% | ISOTONE | 7 | Either of two species of atoms with the same number of neutrons and a different number of protons |
| 45% | ISOTONE | 7 | One of a group of atoms having the same number of neutrons but a different number of protons |
| 41% | ADD | 3 | Find the sum of two or more numbers |
| 41% | ADDED | 5 | Found the sum of two or more numbers |
| 39% | ISOTONES | 8 | Atoms that have the same number of neutrons |
| 39% | ISOMER | 6 | Compound with the same number of atoms in a different arrangement |
| 36% | ISOTOPES | 8 | Atoms with the same number of protons |
| 34% | FUSION | 6 | The process of joining two or more things into one |
| 32% | TANDEM | 6 | Type of bicycle from the 19th century that is built for two or more riders |
| 31% | ION | 3 | Electrically charged atom formed by the loss or gain of one or more electrons |
| 31% | STINGRAY | 8 | Marine creature with one or more venomous spines at the base of the tail |
| 30% | BATONROUGE | 10 | This Capital, one of many with French origins, is one of two states that do not have counties |
| 30% | YANKEES | 7 | The New York ___, MLB team that has won the most number of World Series championships with 27 wins |
| 30% | PAULMCCARTNEY | 13 | Artist with the most number of Grammy nominations in one night without winning, with 9: 2 wds. |
| 30% | NINE | 4 | See 14 Across ... or the number of interconnected Monday puzzles before this one, starting with 3/15 |
| 30% | BOHRIUM | 7 | Element with atomic number 107 which was named after a Danish physicist who studied the structure of atoms |
| 29% | COMPARE | 7 | Weigh the pros and cons of two or more products |
| 29% | CODEBTOR | 8 | One of two who owe the same money |
| 29% | COMPARE | 7 | Weigh up the pros and cons of two or more items |
| 29% | IMIDE | 5 | Name of the chemical group that contains two acyl groups bound to nitrogen, like derivations of Maleic or Phthalic acid |
| 29% | UTES | 4 | One of the two most recent Pac-12 members |
| 29% | TAN | 3 | One of two Crayola colors with the shortest name |
| 29% | ANOTHER | 7 | One more of the same |
| 29% | COUNTERPOINT | 12 | Musical technique; the simultaneous sounding of two or more parts or melodies |
| 29% | COUPLET | 7 | Two lines of poetry with the same rhythm and rhyme |
| 29% | ERIE | 4 | One of two Great Lakes that begins with a vowel |
| 29% | ISOTOPES | 8 | Same number of protons, different neutrons |
| 29% | ANDSUCH | 7 | With more of the same sort |
| 28% | ATHLETICS | 9 | Oakland ___, MLB team and member of the AL West division that is one of the teams with the most World Series titles |