Multiple Choice
Which of the following elements is necessary for the production of thyroid hormone?
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2. Atoms & Elements
Periodic Table: Element Symbols
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Which of the following is an element?
A
Na
B
NH3
C
CO2
D
H2O
Verified step by step guidance1
Understand the definition of an element: An element is a pure substance consisting of only one type of atom, represented by a unique chemical symbol on the periodic table.
Examine each option to determine if it is an element or a compound: NH3 (ammonia) is a compound made of nitrogen and hydrogen atoms; CO2 (carbon dioxide) is a compound made of carbon and oxygen atoms; H2O (water) is a compound made of hydrogen and oxygen atoms.
Identify Na as the chemical symbol for sodium, which is a single element found on the periodic table.
Conclude that Na is an element because it consists of only one type of atom, unlike the other options which are compounds composed of multiple elements.
Remember that chemical formulas with more than one type of atom represent compounds, while a single symbol like Na represents an element.
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