Which of these statements best describes an element?
A An element is composed of three subatomic particles.
B An element is formed when two atoms of the same kind are bonded together.
C An element is formed when two or more different atoms combine chemically.
D An element is composed of identical atoms.
The Correct Answer and Explanation is :
The correct answer is: D. An element is composed of identical atoms.
Explanation:
An element is a pure substance consisting of only one type of atom. Each element is defined by its atomic number, which is the number of protons in the nucleus of its atoms. The atoms of a single element have the same number of protons, though they may have different numbers of neutrons, resulting in isotopes of the element. However, all isotopes of an element share the same chemical properties because they have the same electron configuration.
Why the Other Options Are Incorrect:
- A. An element is composed of three subatomic particles.
While it is true that most atoms consist of protons, neutrons, and electrons, this statement does not specifically define an element. It describes atomic structure in general, which applies to all atoms, not just elements. - B. An element is formed when two atoms of the same kind are bonded together.
This describes a molecule, not an element. For example, two oxygen atoms bonded together form an oxygen molecule (O₂), but the element is oxygen itself, which is composed of individual oxygen atoms. - C. An element is formed when two or more different atoms combine chemically.
This describes a compound, not an element. For example, when hydrogen and oxygen atoms combine chemically, they form water (H₂O), which is a compound.
Characteristics of Elements:
- Elements cannot be broken down into simpler substances by chemical means.
- Each element is represented by a unique chemical symbol (e.g., H for hydrogen, O for oxygen).
- Elements are organized in the periodic table, which arranges them based on their atomic number and properties.
Thus, D is the most accurate description because it emphasizes the identical nature of atoms in an element, which is its defining characteristic.