Atoms, Isotopes, Ions, And Molecules: The Building Blocks

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Anion

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negative ion that is formed by an atom gaining one or more electrons

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atom

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the smallest unit of matter that retains all of the chemical properties of an element

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atomic mass

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calculated mean of the mass number for an element’s isotopes

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atomic number

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total number of protons in an atom

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balanced chemical equation

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statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants

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cation

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positive ion that is formed by an atom losing one or more electrons

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chemical bond

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interaction between two or more of the same or different atoms that results in the formation of molecules

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chemical reaction

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process leading to the rearrangement of atoms in molecules

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chemical reactivity

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the ability to combine and to chemically bond with each other

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compound

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substance composed of molecules consisting of atoms of at least two different elements

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covalent bond

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type of strong bond formed between two of the same or different elements; forms when electrons are shared between atoms

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electrolyte

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ion necessary for nerve impulse conduction, muscle contractions and water balance

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electron

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negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of –1 unit

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electron transfer

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movement of electrons from one element to another; important in creation of ionic bonds

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electronegativity

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ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms

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element

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one of 118 unique substances that cannot be broken down into smaller substances; each element has unique properties and a specified number of protons

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equilibrium

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steady state of relative reactant and product concentration in reversible chemical reactions in a closed system

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hydrogen bond

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weak bond between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules

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inert gas

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(also, noble gas) element with filled outer electron shell that is unreactive with other atoms

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ion

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atom or chemical group that does not contain equal numbers of protons and electrons

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ionic bond

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chemical bond that forms between ions with opposite charges (cations and anions)

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isotope

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one or more forms of an element that have different numbers of neutrons

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mass number

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total number of protons and neutrons in an atom

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matter

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anything that has mass and occupies space

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molecule

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two or more atoms chemically bonded together

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neutron

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uncharged particle that resides in the nucleus of an atom; has a mass of one amu

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noble gas

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element with filled outer electron shell that is unreactive with other atoms

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nonpolar covalent bond

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type of covalent bond that forms between atoms when electrons are shared equally between them

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nucleus

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core of an atom; contains protons and neutrons

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octet rule

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rule that atoms are most stable when they hold eight electrons in their outermost shells

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orbital

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region surrounding the nucleus; contains electrons

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periodic table

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organizational chart of elements indicating the atomic number and atomic mass of each element; provides key information about the properties of the elements

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polar covalent bond

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type of covalent bond that forms as a result of unequal sharing of electrons, resulting in the creation of slightly positive and slightly negative charged regions of the molecule

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product

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molecule found on the right side of a chemical equation

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proton

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positively charged particle that resides in the nucleus of an atom; has a mass of one amu and a charge of +1

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radioisotope

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isotope that emits radiation composed of subatomic particles to form more stable elements

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reactant

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molecule found on the left side of a chemical equation

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reversible chemical reaction

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chemical reaction that functions bi-directionally, where products may turn into reactants if their concentration is great enough

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valence shell

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outermost shell of an atom

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van der Waals interaction

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very weak interaction between molecules due to temporary charges attracting atoms that are very close together