Part of Speech

Noun

Pronunciation

/əˈtɒmɪk ˈnʌmbər/ (uh-TOM-ik NUM-bur)

Definitions

• 1. The number of protons found in the nucleus of an atom, which determines the element's identity and its position in the periodic table.
• 2. A fundamental property of an element, the atomic number is used to uniquely identify each element. It is always a positive integer.

Usage Examples

• The atomic number of hydrogen is 1, and that of helium is 2.
• The periodic table is arranged by atomic number, with each element's atomic number increasing by one as you move across the table.
• When an atom gains or loses electrons, it becomes an ion, but its atomic number remains unchanged.

Etymology

The term "atomic number" comes from the word "atomic," referring to atoms, and "number," which refers to its specific numerical identity based on its number of protons. The concept of atomic number was first introduced by the physicist Henry Moseley in 1913, revolutionizing the arrangement of elements in the periodic table and replacing earlier methods based on atomic mass.

Synonyms

• Proton number
• Element number

Antonyms

• Atomic mass
• Mass number

Translations

Regional Pronunciation Variations

In British English, the pronunciation of "atomic" may sound slightly more clipped compared to American English, where the "o" is often pronounced more distinctly. Regional variations are also seen in non-native English speakers, where local accents can influence how "atomic" and "number" are articulated.

Historical Usage

The concept of atomic number was introduced by the British physicist Henry Moseley in 1913. Before this, the periodic table was arranged based on atomic mass, but Moseley's work established that atomic number, not mass, should be the organizing principle. This discovery clarified the order of elements in the table and explained discrepancies in the properties of elements. Moseley’s work laid the foundation for the modern understanding of atomic structure and periodicity in chemistry.

Cultural Nuances

While the atomic number is a purely scientific concept, it carries significant cultural weight due to its role in the development of the periodic table, the study of chemistry, and physics. Its application in understanding the structure of matter has influenced various technological advancements. In popular culture, elements with certain atomic numbers have become symbols, such as carbon (atomic number 6) being central to life, or uranium (atomic number 92) being associated with nuclear energy and weapons.

More Information

The atomic number is central to the modern classification of elements in the periodic table, which is an essential tool in chemistry, physics, and other sciences. It determines an element's chemical properties and its position in the table. The atomic number is always a unique identifier for each element, and it plays a critical role in nuclear reactions, atomic structure analysis, and spectroscopy. By examining atomic numbers, scientists can infer the number of electrons in an atom and predict how it will bond with other elements. This concept is key in understanding both the simplicity of elemental chemistry and the complexity of atomic physics.