Question

Explain clearly what is meant by the statement"The atomic mass of gold is 197.0 amu."

Short answer

The atomic mass of gold, 197.0 amu, is the average mass of its isotopes.

Step-by-step solution

Understanding Atomic Mass

Atomic mass is the mass of an atom expressed in atomic mass units (amu). It represents the average mass of all the isotopes of an element, taking into account their relative abundance.

Analyzing the Statement

The statement 'The atomic mass of gold is 197.0 amu' means that the average mass of a gold atom, considering the relative abundance of its isotopes, is 197.0 atomic mass units.

Interpreting the Atomic Mass of Gold

The atomic mass of 197.0 amu for gold indicates that a single atom of gold weighs 197.0 amu. This value reflects the weighted average mass of all naturally occurring isotopes of gold.

Key concepts

Isotopes

Isotopes are variations of the same element that contain the same number of protons but differ in the number of neutrons. This difference in neutron number gives isotopes different mass numbers. For example, carbon has isotopes like Carbon-12 and Carbon-14, where the number refers to their mass numbers. It's essential to understand that while isotopes vary in some properties, they share chemical properties since they have the same number of protons and electrons.
In elements like gold, isotopes contribute to calculating atomic mass. Each isotope has a specific abundance, and this influences the average atomic mass you see on the periodic table. For gold, nearly all its naturally occurring atoms are composed of one stable isotope, allowing the atomic mass to be quite specific, like the 197.0 amu mentioned.

Atomic Mass Units (amu)

Atomic Mass Units (amu) are a standard unit of mass used to express atomic and molecular weights. The atomic mass unit is defined as one-twelfth of the mass of a carbon-12 atom, roughly equal to the mass of one proton or neutron. Thus, it provides us with a practical way to express the very tiny masses of atoms and molecules.
When you read that gold has an atomic mass of 197.0 amu, it tells us how gold compares to other elements, making it easier to study and compare atoms in chemistry. This standardized measurement helps scientists, students, and educators convey clear, concise information about atom masses.

Element Gold

Gold, symbolized as 'Au' from its Latin name 'Aurum', is a dense, precious metallic element known for its yellow luster and resistance to tarnish. It has significant economic and cultural value and is extensively used in jewelry, investments, and electronics due to its high conductivity and non-corrosive nature.
In terms of atomic structure, gold is unique because it predominantly consists of one natural isotope, Au-197, which is why its atomic mass is an almost exact 197.0 amu. Compared to other elements with multiple naturally occurring isotopes, gold's atomic mass is simpler to pinpoint. This consistency gives gold its appealing purity and stable properties, leading to its extensive use and value across the world.