Final answer:
A gold bar is an example of an element, which is a type of pure substance made up of only one kind of atom, and gold is represented by the symbol Au on the periodic table.
Step-by-step explanation:
When we look at gold bars, we are observing a type of pure substance that cannot be broken down into simpler substances through chemical changes. According to your questions and the provided information, a gold bar is an example of an element, which fits into option D from Column B. Elements are pure substances that are made up of only one type of atom, and they cannot be converted or decomposed into simpler substances by ordinary chemical means.
Gold, represented by the symbol Au on the periodic table, is indeed an element that is composed of particles known as atoms. This can be visualized in Figure 2.1.1, where a magnified section of the gold surface would show a packing of gold atoms. Pure substances can be divided into elements and compounds; gold is one of the more than 100 known elements and is familiar to us due to its distinctive yellowish color and properties.