Elements and Compounds

Match each term with its correct definition.

• The smallest particle of an element; made up of electrons, protons, and neutrons

• Atom

• A one- or two-letter notation used to represent an atom of a particular element

• Element

• The simplest unit of a chemical compound that can exist; formed when two or more atoms join together chemically

• Chemical symbol

• A new substance with unique chemical and physical properties formed when two or more elements are chemically bonded during a chemical reaction

• Molecule

• A pure substance composed of the same type of atom throughout

• Compound

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Label this chemical formula with the correct words.

a

b

c

d

Coefficient

Compound

Subscript

Chemical formula

Elements and compounds are similar because they are both pure substances, but they are different because elements consist of only one type of atom, while compounds are made of two or more types of atoms chemically combined. Which statement best describes how elements and compounds are similar and different?

• Both are pure substances, but elements have one type of atom and compounds have two or more types of atoms chemically combined.

• Both are mixtures, but elements are made of molecules and compounds are made of atoms.

• Elements and compounds are both made of only one type of molecule.

• Elements are always gases, while compounds are always solids.

A scientist is given a compound represented by the chemical formula NaHCO₃. Which of the following correctly identifies the atoms and the number of atoms in the compound?

• 1 sodium, 1 hydrogen, 1 carbon, 3 oxygen atoms

• 2 sodium, 1 hydrogen, 1 carbon, 3 oxygen atoms

• 1 sodium, 2 hydrogen, 1 carbon, 3 oxygen atoms

• 1 sodium, 1 hydrogen, 2 carbon, 3 oxygen atoms

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How are the two substances shown below different?

• Substances 1 and 2 are both elements.

• Substances 1 and 2 are both molecules.

• Substance 1 is a molecule, and substance 2 is an atom.

• Substance 1 is an atom, and substance 2 is a molecule.

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Use the Periodic Table to identify the atoms and number of each type of atom in the following chemical formula: SO₄.

• Sodium: 1, Oxygen: 4

• Sulfur: 1, Oxygen: 4

• Sodium: 0, Oxygen: 4

• Sulfur: 0, Oxygen: 4

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Observe the information in the images below. Which of the following statements is true about the images?

• Image X and Image Y are both elements.

• Image X and Image Y are both compounds.

• Image X is a compound, and Image Y is an element.

• Image X is an element, and Image Y is a compound.

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How many atoms of Oxygen are in the chemical formula below? C₆H₁₂O₆

• 12

• 18

• 6

• 24

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Elements and compounds are similar in some ways but different in others. They differ because–

• elements are made of only one type of atom, while compounds are made of a combination of two or more atoms of different elements.

• elements are made of a combination of two or more atoms of different elements, and compounds are made of only one type of atom.

• elements are made of a combination of two of the same atoms, and compounds are made of a combination of two or more atoms of different elements.

• elements are made of a combination of two or more atoms of different atoms, and compounds are made of a combination of two or more of the same atoms.

Which elements are found in the compound below? C₆H₁₂O₆ Select three correct answers.

• Cobalt

• Oxygen

• Carbon

• Helium

• Hydrogen

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