About this Flash Card Set
16 Cards
by ethan_walsh
The building blocks of chemistry: atoms, subatomic particles, isotopes, and how the periodic table is organized. Clear definitions for intro chemistry students.
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Atom
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The smallest unit of an element that retains its chemical properties. Made of protons, neutrons, and electrons.
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Proton
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Positively charged particle in the nucleus. The number of protons (atomic number) defines the element.
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Neutron
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Neutral (no charge) particle in the nucleus. Adds mass and affects which isotope an atom is.
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Electron
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Negatively charged particle that occupies regions (orbitals) around the nucleus. Involved in bonding and chemical reactions.
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Atomic number
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The number of protons in an atom's nucleus. It identifies the element and its place on the periodic table.
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Mass number
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The total number of protons plus neutrons in an atom's nucleus.
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Isotopes
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Atoms of the same element (same protons) with different numbers of neutrons — same chemistry, different mass.
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Ion
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An atom or molecule with a net electric charge from gaining or losing electrons. Cation = positive, anion = negative.
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Periodic table
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A chart of all elements arranged by increasing atomic number, grouped so elements with similar properties fall in the same column.
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Group (family)
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A vertical column of the periodic table. Elements in a group have similar chemical properties and the same number of valence electrons.
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Period
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A horizontal row of the periodic table. Across a period, properties change gradually as atomic number increases.
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Valence electrons
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Electrons in an atom's outermost shell. They determine how an atom bonds and reacts.
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Metals vs. nonmetals
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Metals (left/center) are shiny, conductive, and lose electrons easily. Nonmetals (upper right) are poor conductors and tend to gain electrons.
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Noble gases
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Group 18 elements (He, Ne, Ar...) with full valence shells, making them very stable and largely unreactive.
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Element vs. compound
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An element is made of one type of atom; a compound is two or more different elements chemically bonded (e.g., H₂O).
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Atomic mass (on the table)
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The weighted average mass of an element's isotopes, shown under the symbol on the periodic table.
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