Multiple Choice
Which of the following is the atomic number of gold (Au)?
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2. Atoms & Elements
Periodic Table: Element Symbols
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Which of the following is an example of a chemical element?
A
Na
B
H2O
C
NH3
D
CO2
Verified step by step guidance1
Understand that a chemical element is a pure substance consisting of only one type of atom, represented by a unique chemical symbol on the periodic table.
Look at each option and identify whether it is a single element or a compound made of multiple elements bonded together.
Recognize that 'Na' is the chemical symbol for sodium, which is a single element.
Note that 'H2O' (water), 'NH3' (ammonia), and 'CO2' (carbon dioxide) are chemical compounds composed of two or more different elements chemically bonded.
Conclude that among the options, only 'Na' represents a chemical element.
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