What occurs in both fusion and fission reactions?
(1) small amounts of energy are converted into
large amounts of matter.
(2) small amounts of matter are converted into
large amounts of energy.
(3) heavy nuclei are split into lighter nuclei.
(4) light nuclei are combined into heavier nuclei

I believe the correct answer from the choices listed above is option 2. Small amounts of matter are converted into
large amounts of energy occurs in both fusion and fission reactions. They are nuclear reactions where a change in the identity or characteristics of an atomic nucleus results when it is bombarded with an energetic particle, as in fission, fusion, or radioactive decay.

Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.