A form of technetium -99 has a half-life of approximately 6 hours (}_{43)^99TCarrow underline ( )+_(-1)^0e+gamma Which substance correctly completes the equation above? A (}_{42)^99Mo B (}_{43)^94Te C (}_{43)^99Es D (}_{44)^99Ru

## Step 1<br />The problem involves a nuclear decay process, specifically beta decay. In beta decay, a neutron in the nucleus of an atom is converted into a proton, an electron (also known as a beta particle), and an antineutrino. The atomic number increases by one, but the atomic mass number remains the same.<br /><br />## Step 2<br />In this case, the parent atom is Technetium-99 (Tc), which has an atomic number of 43. The atomic mass number remains the same, so the atomic number of the daughter atom must be 44.<br /><br />## Step 3<br />Looking at the options, only option A, Molybdenum-99 (Mo), has an atomic number of 44. Therefore, it is the correct answer.