Problem 3 - Biology Concepts and Applications

Question

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

Step-by-Step Solution

Answer

The incorrect statement is d: Free radicals are dangerous because they emit energy.

Step 1: Read the Question

We need to identify which statement among the given options is incorrect. Each statement will be evaluated based on scientific facts.

Step 2: Evaluate Option A

Statement a claims that isotopes have the same atomic number but different mass numbers. Isotopes indeed have the same number of protons (atomic number) and vary in their number of neutrons (mass number), making this statement correct.

Step 3: Evaluate Option B

Statement b claims that atoms have about the same number of electrons as protons. Atoms are electrically neutral, meaning they usually have the same number of electrons and protons. Thus, this statement is correct.

Step 4: Evaluate Option C

Statement c claims that all molecules consist of atoms. By definition, molecules are comprised of two or more atoms bonded together. Hence, this statement is correct.

Step 5: Evaluate Option D

Statement d claims that free radicals are dangerous because they emit energy. Free radicals are indeed dangerous due to their high reactivity, not because they emit energy. Thus, this statement is incorrect.

Key Concepts

Isotopes

Isotopes are variations of the same chemical element that have identical atomic numbers but differ in their mass numbers. To break it down further, the atomic number represents the number of protons in the nucleus of an atom. Since isotopes have the same atomic number, they possess the same number of protons. However, what sets isotopes apart is their neutron count.
This difference in the number of neutrons results in varying mass numbers (the sum of protons and neutrons) among isotopes. For example:

• Carbon-12 and Carbon-14 are isotopes of Carbon. They both have 6 protons (hence they are still carbon atoms) but Carbon-12 has 6 neutrons while Carbon-14 has 8 neutrons.

Understanding isotopes is essential in fields like chemistry and biology because it influences the atomic weight of elements and has applications in radiometric dating, medical diagnostics, and treatment.

Atoms and Molecules

Atoms are the basic building blocks of matter. They combine to form molecules, which are groups of two or more atoms bonded together. Molecules can consist of similar atoms, like \(O_2\), or different atoms, like \(H_2O\).
This combination process is called chemical bonding and can occur through covalent or ionic bonds, leading to the formation of substances with unique properties compared to the individual atoms.To sum it up:

• Atoms are the smallest unit of matter retaining the properties of an element.
• Molecules are combinations of two or more atoms bonded together.

It's important to speak of molecules in chemistry because they explain how various substances behave, interact, and form compounds that are essential to life and the universe.

Free Radicals

Free radicals are atoms or molecules that have an unpaired electron, which makes them highly reactive. Because of this reactivity, free radicals are often involved in chemical reactions aiming to achieve stability by pairing their lone electron with another. Why are they considered dangerous?

• Due to their instability, free radicals can cause cellular damage. This damage may contribute to aging and various diseases, including cancer.
• Free radicals are not dangerous because they emit energy, rather their reactivity makes them prone to destructive interactions with critical biomolecules such as DNA, proteins, and lipids.

Managing free radicals is essential for maintaining health. Antioxidants, for example, neutralize free radicals by donating an electron without becoming unstable themselves, thus lowering the risk of cell damage.