Elements, Molecules and Compounds

What determines the type of element an atom makes?

• The size of the nucleus
• The number of protons
• How much an atom weighs
• The number of neutrons

Humans absorb oxygen from the air they breathe in and exhale carbon dioxide gas, CO2. Carbon dioxide gas is

• an element made of carbon and oxygen atoms.

• a solution made of carbon and oxygen atoms.

• a compound of carbon and oxygen atoms.

• a mixture of carbon and oxygen atoms.

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How many Hydrogen atoms are present in H₂0?

• 2

• 4

• 1

• 0

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Hydrogen is a pure substance represented by the chemical symbol H. Which of the following best describes hydrogen?

• Hydrogen is an element made of two or more kinds of atoms.
• Hydrogen is a compound made of only one kind of atom.
• Hydrogen is a compound made of two or more kinds of atoms.
• Hydrogen is an element made of only one kind of atom.

Which one of the following is a compound?

• NaCl

• O2

• Hydrogen

• He2

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Which of the following is NOT a compound?

Nitrous Oxide (N₂O)

Ozone (O₃)

Carbon Dioxide (CO₂)

Dihydrogen Monoxide (H₂O)

• Ozone (O₃)

• Nitrous Oxide (N₂O)

• Carbon Dioxide (CO₂)

• Water (H₂O)

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These are what form chemical bonds as atoms share or take them from one another.

• electrons

• electron clouds

• protons

• neutrons

Carbon (C) and hydrogen (H) are pure substances. Each is made of only one type of atom, but carbon atoms are different from hydrogen atoms. Carbon and hydrogen chemically combine to form methane (CH4).

• methane is an element and carbon and hydrogen are compounds.
• carbon, hydrogen, and methane are all elements.
• carbon, hydrogen, and methane are all compounds.
• carbon and hydrogen are elements and methane is a compound.

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A compound is...

• a substance made up of one type of atom in its molecular form.
• a substance formed by the reaction of two or more elements.
• a mixture formed by the mixing of two or more elements.
• a substance made up of one type of atom in its atomic form.

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How many different elements are represented in the compound?
H₂O₂

• 2
• 3
• 1
• 4

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