An element is determined by the number of:
A. Atoms
B. Electrons
C. Neutrons
D. Protons
The correct answer and explanation is:
The correct answer is D. Protons.
Explanation:
An element is defined by the number of protons in the nucleus of its atoms. This number is called the atomic number and is unique to each element. For example, hydrogen has one proton, helium has two protons, and carbon has six protons. The atomic number determines the identity of the element because the chemical properties of an atom depend primarily on the number of protons it contains.
Atoms consist of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus, while electrons orbit around the nucleus. Although electrons influence chemical behavior and bonding, they do not determine the element itself. This is because atoms can gain or lose electrons and form ions, yet still remain the same element as long as the number of protons remains constant.
Neutrons contribute to the mass of an atom and can vary within atoms of the same element. Atoms with the same number of protons but different numbers of neutrons are called isotopes. Isotopes of an element share chemical properties but may have different physical properties and stability.
Atoms themselves are the smallest units of an element that retain its chemical properties. However, the element is not defined by the total number of atoms but by the number of protons in each atom’s nucleus.
In summary, the defining characteristic of an element is the number of protons. This atomic number uniquely identifies the element and determines its position in the periodic table. Changes in the number of neutrons create isotopes, while changes in the number of electrons create ions. Only a change in the number of protons transforms one element into another.