Chemistry Concepts

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Atom

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The smallest unit of an element that keeps its properties.

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Element

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A pure substance made of only one type of atom. Example: Gold (Au), Oxygen (O₂).

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Compound

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A pure substance formed when two or more different elements bond chemically. Example: Water (H₂O), Salt (NaCl).

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Molecule

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Two or more atoms combined in fixed proportions

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Mixture

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Matter made of two or more different types of substances or particles

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Solution

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A homogeneous mixture made of different particles that blend uniformly

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Pure Substance definition

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Made of only 1 type of particle

(Elements and compounds)

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Valence Electrons

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The electrons in the outermost shell of an atom; they determine chemical reactivity.

Elements in the same group on the periodic table have the same number of valence electrons

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Neutron

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Found in the nucleus and has a neutral charge

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Electron

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small and move very fast outside of the nucleus