Exam 5 - Regular Chemistry - Krug

The correct answer is "half life". The half life of a radioactive isotope refers to the time it takes for half of the atoms in a sample to decay. It is a measure of the rate of decay and is a characteristic property of each radioactive isotope. The concept of half life is important in various fields such as nuclear physics, medicine, and archaeology, as it helps determine the age of materials and the behavior of radioactive substances.

Fluorine is located in Group 7A of the periodic table, also known as Group 17. Elements in this group, called halogens, have 7 valence electrons. Valence electrons are the electrons in the outermost energy level of an atom and are involved in chemical bonding. Therefore, a typical atom of fluorine would have 7 valence electrons.

A single line drawn between the atoms in a structural formula represents a shared pair of electrons. In a covalent bond, atoms share electrons to achieve a stable electron configuration. The single line indicates that two electrons are being shared between the atoms, forming a single bond. This type of bond is typically formed between two nonmetal atoms.

In the given question, we are asked to identify the central atom in the molecule. The central atom is the atom that is bonded to multiple other atoms in the molecule. Among the options given, nitrogen is the only atom that can form multiple bonds with other atoms. Hydrogen can only form one bond, while neon and helium are noble gases and do not typically form bonds. Therefore, nitrogen is the correct answer as it is likely to be the central atom in the molecule.

The octet rule states that most elements are most stable when they have a full outer electron shell, which consists of 8 valence electrons. This is because having a full outer shell allows the element to have a stable electron configuration similar to that of the noble gases. Therefore, the correct answer is 8.

Alpha particles are represented by the symbol α. They are made up of two protons and two neutrons, giving them a positive charge of +2. Alpha particles are emitted during certain types of radioactive decay, such as alpha decay. They have a relatively large mass and a low penetrating power, which means they can be stopped by a sheet of paper or a few centimeters of air.

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An average American's radiation mostly comes from natural sources. These include cosmic radiation from space, radon gas in homes, and radioactive materials in the earth's crust. Atomic fallout, microwave ovens, and x-rays also contribute to radiation exposure, but they are not the primary sources for the average American.

In a molecule, every single bond consists of two electrons. This is because a single bond is formed when two atoms share one pair of electrons. Therefore, the correct answer is two.

The molecule N2O consists of two nitrogen atoms and one oxygen atom. Each nitrogen atom contributes 5 valence electrons, and the oxygen atom contributes 6 valence electrons. Therefore, the total number of valence electrons in N2O is 2(5) + 6 = 16.

Resonance structures refer to multiple correct representations of a molecule's electron distribution. In this case, the molecule has two valid Lewis electron-dot structures, indicating that the electrons can be arranged in different ways within the molecule without changing its overall structure. These resonance structures are important in understanding the stability and reactivity of the molecule, as they contribute to its overall electronic behavior.

The diagram represents nuclear fission. Nuclear fission is a process in which the nucleus of an atom splits into two or more smaller nuclei, releasing a large amount of energy. This process is typically initiated by bombarding the nucleus with neutrons, causing it to become unstable and break apart. The diagram likely shows the initial nucleus, the neutrons, and the resulting smaller nuclei after the fission reaction has occurred.

Radon is a radioactive gas that can leak into basements and is known to cause lung cancer. It is a colorless and odorless gas that is formed from the natural decay of uranium and radium in the soil. Radon can seep into buildings through cracks and gaps in the foundation, accumulating in enclosed spaces such as basements. Prolonged exposure to high levels of radon can increase the risk of developing lung cancer, making it a significant health concern. Therefore, radon is the correct answer in this case.

Nuclear power plants most commonly use uranium as the radioactive element. Uranium is a widely used fuel in nuclear reactors due to its high energy content and abundance. It undergoes a process called nuclear fission, where its atoms split apart, releasing a large amount of energy. This energy is then used to generate electricity. Carbon, polonium, and radon are not commonly used in nuclear power plants for energy production.

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Hydrogen is an exception to the octet rule because it can only form a maximum of two bonds, not eight like the other elements listed. This is because hydrogen only has one electron in its outer shell, so it can only share that electron with another atom to form a bond. Therefore, hydrogen does not follow the octet rule, which states that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with eight electrons in their outermost shell.

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The symbol for a radioactive nuclide with 17 protons and 19 neutrons is Cl-36.

The type of radiation with the symbol  can be stopped with a thick lead wall because lead is a dense material that is effective at absorbing and blocking radiation. The thickness of the lead wall ensures that the radiation particles do not pass through and reach the other side. Paper, plywood, and aluminum are not dense enough to effectively stop this type of radiation and would allow it to pass through.

In the correct Lewis structure for the molecule, there are no unshared electron pairs surrounding the carbon atom. This means that all of the electrons are involved in bonding with other atoms, and there are no lone pairs of electrons on the carbon atom itself.

The correct structural formula for CH2O is a carbon atom bonded to two hydrogen atoms and one oxygen atom. The carbon atom is the central atom, with the hydrogen atoms bonded to it and the oxygen atom bonded to the carbon atom. This arrangement satisfies the valence electron requirements for each atom, with carbon having four valence electrons, hydrogen having one valence electron, and oxygen having six valence electrons.

A radiation dose of 5 rem in a human would most likely result in nothing. This is because 5 rem is considered a relatively low dose of radiation, and the effects of radiation exposure are generally not significant at this level. While higher doses can cause symptoms such as nausea and vomiting, and extremely high doses can be fatal, a dose of 5 rem is unlikely to have any noticeable immediate effects on the individual.

Nuclear fusion is the process in which two atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy. This phenomenon occurs naturally in the sun and stars, where the immense gravitational pressure and high temperatures create the conditions necessary for fusion reactions to take place. In nuclear power plants, controlled fusion reactions are still being researched and developed as a potential future energy source. Smoke detectors and vehicle exhaust pipes, on the other hand, do not involve nuclear fusion but rather rely on other mechanisms for their functioning.

The half-life of a radioactive isotope is the time it takes for half of the substance to decay. In this case, the half-life is 30 minutes. So, after 30 minutes, the amount of the isotope will be reduced to 50 grams. Another 30 minutes will pass, and the amount will be reduced to 25 grams, which is half of the previous amount. Therefore, it will take a total of 60 minutes for the amount to drop from 100 grams to 25 grams.

The correct answer is "less than 1 rem" because the average American is exposed to a small amount of radiation over the course of one year. The unit "rem" stands for "roentgen equivalent man" and is used to measure the biological effects of radiation. The average annual radiation exposure for an American is typically less than 1 rem, which is considered to be a low level of exposure.

A positron is the symbol for a type of ionizing radiation. Positrons are positively charged particles that are the antiparticles of electrons. When a positron collides with an electron, they annihilate each other and produce gamma rays. Therefore, the correct answer is positron.

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The half-life of a radioactive isotope is the time it takes for half of the initial amount of the isotope to decay. In this case, the isotope decreases from 60 grams to 7.5 grams over a period of 100 seconds. To find the half-life, we need to determine the time it takes for the isotope to decrease to half of its initial amount, which is 60 grams divided by 2, or 30 grams. Since the isotope decreases from 60 grams to 30 grams in 33.3 seconds, the half-life is 33.3 seconds.

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A high-powered electron emitted by a radioactive nucleus is called a beta particle. Beta particles are produced during beta decay, a type of radioactive decay where a neutron in the nucleus is converted into a proton and an electron. The electron is then emitted from the nucleus as a beta particle. Beta particles have a negative charge and relatively low mass compared to alpha particles and neutrons. They can penetrate matter to a certain extent and are commonly used in medical imaging and radiation therapy.