4. Nuclear reactions Aa Aa Uranium is an element with three naturally occurring

Question

4. Nuclear reactions Aa Aa Uranium is an element with three naturally occurring isotopes: 238U, 235U, and 234U. This means that 238U, which has a mass number of 238, has more than 235U, which has a mass number of 235 electron s) neutron(s) proton(s) e determined by its half-life. Half-life, by definition, means Each different radioactive isotope decays the time it takes for half of the total amount of radioactive "parent" atoms to decay into different "daughter" atoms Knowing the half-life and concentrations of parent and daughter atoms in various samples found in nature allows scientists to date objects such as rocks and fossils. For example, the half-life of 238U is 4.5 billion years, which means that, for a given sample, half of all 238U atoms (the parent) decays into 206Pb atoms (its daughter) during this time Given this rate of decay, 238U has been used to help determine the age of meteorites, ancient rocks, and even the age of the earth However, 238U decays into 206Pb not in a single step but in a series of decays into other elements, and in the process emits fast moving particles (called alpha and beta particles) 4He Emitted particle Parent nucleus Decay The first reaction of this decay series is shown in the figure on the left. In this reaction, 238U decays into an alpha particle (a helium atom with two protons and two neutrons) and thorium (234Th) 238U event 234Th Daughter nucleus Compare the total number of protons (blue) and neutrons (grey) in the reactant with the total number of protons and neutrons in the products of this reaction by using the following dropdown menus 238U 4He 234Th energy Total protons and neutrons Total protons and neutrons

Explanation / Answer

1- neutrons

2-equal to , conserved

3-25%

Lets assume the total energy is 100% to bind the neucleons of 238U . 40% is transfered to bind the He and 35% is for the Th neucleons . so rest energy must have released as heat energy , so released energy must have been (100-(40+35))% .= 25%

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