Question

Which of the following statements is incorrect? a. Isotopes have the same atomic number and different mass numbers. b. All molecules consist of atoms. c. Free radicals are dangerous because they emit energy.

Short answer

Statement C is incorrect.

Step-by-step solution

Analyze Statement A

Statement A mentions that isotopes have the same atomic number and different mass numbers. This is correct because isotopes of a given element have the same number of protons (atomic number) but different numbers of neutrons, which leads to different mass numbers.

Analyze Statement B

Statement B states that all molecules consist of atoms. This is also correct as a molecule is a chemical structure that consists of at least two atoms bonded together.

Analyze Statement C

Statement C claims that free radicals are dangerous because they emit energy. This is incorrect. Free radicals are highly reactive due to the presence of unpaired electrons, and they can cause damage to cells in the body, but this is not because they emit energy.

Conclusion

Based on the analysis of each statement, Statement C is the incorrect one.

Key concepts

Atomic Number

The atomic number is a fundamental concept in understanding isotopes and elements. It is defined as the number of protons in the nucleus of an atom, and it uniquely identifies a chemical element. The atomic number determines the element's position on the periodic table. For example, carbon has an atomic number of 6, meaning every carbon atom has 6 protons.

It's important because this number stays constant for all atoms of an element, while other properties, like the number of neutrons, can vary. This constancy is why isotopes of an element all have the same atomic number but differ in mass number.

Understanding the atomic number helps in identifying not only the element itself but also its chemical behavior and properties.

Mass Number

Mass number is another crucial concept when discussing isotopes. It is defined as the total number of protons and neutrons in an atom's nucleus. While the number of protons (atomic number) is consistent for an element, the number of neutrons can vary, leading to different mass numbers for isotopes.

For example, let's consider the isotopes of hydrogen: Proteium has a mass number of 1 (1 proton and 0 neutrons), Deuterium has a mass number of 2 (1 proton and 1 neutron), and Tritium has a mass number of 3 (1 proton and 2 neutrons).

The mass number helps in identifying the isotopic form of an element and plays a crucial role in understanding the isotope's weight and stability.

Free Radicals

Free radicals are atoms or molecules that have unpaired electrons, making them highly reactive. They tend to seek stability by stealing electrons from other molecules, often causing damage in the process. This high reactivity is what makes free radicals potentially harmful, particularly in biological systems.

Free radicals can be generated in the body through normal metabolic processes or introduced from external sources like pollution, radiation, and tobacco smoke.

While they do indeed cause damage, it's not because they emit energy. Instead, it's due to their tendency to attack surrounding molecules, which can lead to cell damage and contribute to conditions such as cancer and aging. Understanding free radicals is crucial in biology and medicine for developing antioxidants that can neutralize these harmful particles.