Compounds

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Element Noun

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[el-uh-muhnt]

Back

Element

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A pure substance consisting of only one type of atom, which cannot be broken down by chemical means.

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Example: This diagram shows a model of an oxygen atom, an example of an element. All elements are made of only one type of atom.

Front

Atom Noun

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[at-uhm]

Back

Atom

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The smallest unit of an element that maintains the chemical properties of that element.

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Example: This diagram shows an atom's structure: a central nucleus with protons and neutrons, surrounded by electrons orbiting in shells. This is the basic unit of matter.

Front

Compound Noun

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[kom-pound]

Back

Compound

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A unique substance that forms when two or more different elements combine chemically in a fixed proportion.

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Example: This image shows a molecule of carbon dioxide (CO₂), a compound made of one carbon atom chemically bonded to two oxygen atoms.

Front

Molecule Noun

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[mol-i-kyool]

Back

Molecule

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The smallest particle of a substance, consisting of two or more atoms chemically bonded together.

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Example: This diagram shows a single water molecule (H₂O), which is formed when one oxygen atom chemically bonds with two hydrogen atoms.

Front

Valence Shell Noun

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[vey-luhns shel]

Back

Valence Shell

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The outermost electron shell of an atom that is involved in forming chemical bonds with other atoms.

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Example: This diagram shows two oxygen atoms sharing electrons from their outermost shell, the valence shell, to form a stable bond and create an oxygen molecule.

Front

Octet Rule Noun

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[ok-tet rool]

Back

Octet Rule

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A chemical rule describing an atom's tendency to have a full valence shell with eight electrons.

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Example: An oxygen atom, with six outer electrons, shares electrons with two hydrogen atoms to achieve a stable, full outer shell of eight electrons (an octet).

Front

Chemical Bond Noun

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[kem-i-kuhl bond]

Back

Chemical Bond

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A lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds.

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Example: This model shows how two hydrogen (H) atoms and one oxygen (O) atom are held together by chemical bonds to form a water molecule.

Front

Covalent Bond Noun

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[koh-vey-luhnt bond]

Back

Covalent Bond

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A type of chemical bond that involves the sharing of valence electrons between atoms to form a molecule.

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Example: Two non-metal atoms share their outer electrons (valence electrons) to form a stable bond, creating a covalent molecule.

Front

Ionic Bond Noun

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[ahy-on-ik bond]

Back

Ionic Bond

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A chemical bond formed through electrostatic attraction between oppositely charged ions after the transfer of electrons.

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Example: A metal atom transfers an electron to a nonmetal atom, creating oppositely charged ions that attract each other to form an ionic bond.

Front

Ion Noun

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[ahy-on]

Back

Ion

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An atom or molecule that has a net electrical charge due to the loss or gain of electrons.

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Example: A neutral sodium atom gives one electron to a neutral chlorine atom, forming a positive sodium ion (Na+) and a negative chloride ion (Cl-).