What is the main difference between elements and compounds?

• Elements are made of one type of atom, while compounds are made of two or more different types of atoms.

• Elements are always metals, while compounds are always non-metals.

• Elements can be broken down into simpler substances, while compounds cannot.

• Elements are found in nature, while compounds are man-made.

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Which of the following is an example of a compound?

• Sodium chloride (NaCl)

• Hydrogen (H2)

• Oxygen (O2)

• Iron (Fe)

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What elements make up the compound H2O?

• Hydrogen and Nitrogen

• Hydrogen and Oxygen

• Hydrogen and Chlorine

• Oxygen and Sodium

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What does the periodic table list?

• All known mixtures

• All known molecules

• All known elements

• All known compounds

How many different compounds are possible by combining elements?

• Billions

• Hundreds

• Thousands

• Millions

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What is a pure substance?

• A substance that is always a compound

• A substance that can be broken down into simpler substances

• A substance with a definite and constant composition

• A mixture of different elements

Which of the following is a pure compound?

• Iron (Fe)

• Water (H2O)

• Oxygen (O2)

• Nitrogen (N2)

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What are diatomic molecules?

• Molecules made of two atoms of the same element

• Molecules made of three atoms

• Molecules made of two different elements

• Molecules made of one atom

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Which of the following is a molecular element?

• H2

• CO2

• NaCl

• H2O

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What is the special name given to molecules like H2 and O2?

• Ionic compounds

• Covalent compounds

• Molecular elements

• Metallic elements

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