Use the following information to answer the question. The element (}^238_{92)U undergoes radioactive decay until it attains a stable state as (}^206_{82)Pb . The first four stages of this decay series are as follows: (}^238_{92)Uarrow ^234_(90)Tharrow ^234_(91)Paarrow ^234_(92)Uarrow ^230Th The particles emitted in each of these steps,respectively, are A. alpha, beta, beta, alpha B. beta, alpha, alpha.beta C. alpha, gamma, gamma alpha D. gamma, alpha, alpha,gamma

The correct answer is A. alpha, beta, beta, alpha. Here's why:<br /><br />* **Understanding Radioactive Decay:** Radioactive decay involves the emission of particles from an unstable nucleus to achieve a more stable configuration. The main types of decay are alpha, beta, and gamma.<br /><br />* **Alpha Decay (α):** An alpha particle consists of 2 protons and 2 neutrons (essentially a helium nucleus). During alpha decay, the atomic number decreases by 2, and the mass number decreases by 4.<br /><br />* **Beta Decay (β):** A beta particle is a high-energy electron. During beta decay, a neutron in the nucleus converts into a proton and an electron (the beta particle). The atomic number increases by 1, and the mass number remains the same.<br /><br />* **Gamma Decay (γ):** Gamma decay involves the emission of high-energy photons (gamma rays). It doesn't change the atomic number or mass number; it simply releases excess energy from the nucleus.<br /><br />* **Analyzing the Decay Series:** Let's examine each step:<br /><br /> 1. ${}^{238}_{92}U \rightarrow {}^{234}_{90}Th$: The mass number decreases by 4, and the atomic number decreases by 2. This indicates **alpha decay**.<br /><br /> 2. ${}^{234}_{90}Th \rightarrow {}^{234}_{91}Pa$: The mass number stays the same, and the atomic number increases by 1. This indicates **beta decay**.<br /><br /> 3. ${}^{234}_{91}Pa \rightarrow {}^{234}_{92}U$: The mass number stays the same, and the atomic number increases by 1. This indicates **beta decay**.<br /><br /> 4. ${}^{234}_{92}U \rightarrow {}^{230}_{90}Th$: The mass number decreases by 4, and the atomic number decreases by 2. This indicates **alpha decay**.<br /><br /><br />Therefore, the sequence of emitted particles is alpha, beta, beta, alpha.<br />