Chemistry Vocabulary

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alkali metal

Back 1

an element of Group 1

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alkaline earth metal

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an element of Group 2

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atom

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the smallest particle of an element that can enter into a chemical reaction

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atomic mass

Back 4

the average mass of all the isotopes in a sample of an element

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atomic number

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the number of protons in the nucleus of an atom

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Avogadro's number

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the number of representative particles contained in one mole of a substance; equal to 6.02 x 10^23

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boiling point

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the temperature at which the vapor pressure of a liquid is equal to the atmospheric pressure

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chemistry

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the study of the composition of matter and changes that occur in it

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coefficient

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the number placed before a formula indicating the number of units of that substance

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combustion

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an exothermic reaction with oxygen, releasing heat

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compound

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a substance composed of two or more elements that are chemically combined in definite proportions by mass

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condensation

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an exothermic procession which a vapor or a as changes into the liquid phase

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decomposition

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a chemical reaction in which a compound is broken down into simpler substances

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diatomic molecule

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a molecule containing two identical atoms

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double replacement

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a chemical reaction in which ions exchange places

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electron

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a fundamental particle of matter having a negative charge

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electron configuration

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the distribution of electrons in an atom

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electronegativity

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a measure of the attraction of a nucleus for a bonded electron of another atom's

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element

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substances that cannot be broken down or decomposed into simpler substances by chemical means

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empirical formula

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the simplest integer ratio in which atoms combine to form a compound

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endothermic

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a chemical reaction that absorbs heat, producing products with more potential energy than the reactants.

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evaporation

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the process by which molecules in the liquid phase escape into the gaseous phase.

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excited state

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the condition that exists when the electrons of an atom occupy higher energy levels while lower energy levels are vacant

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exothermic

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chemical reaction that releases heat, producing products with less potential energy than the reactant

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family

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a vertical column on the periodic table (groups)

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fermentation

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an organic reaction in which ethanol and carbon dioxide are produced from a carbohydrate

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formula mass

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the use of the atomic masses of all atoms present

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formula

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symbols and subscripts used to represent the composition of substance

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freezing point

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the constant temperature in which particles in the liquid phase lose energy and change into the solid phase (solidification)

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freezing

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the constant temperature at which both the solid and liquid poses of a substance exist in equilibrium; the same temperature as the substance's melting point.

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gaseous phase

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a phase of matter without definite shape or volume

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gram formula mass

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the formula mass expressed in grams instead of atomic mass units

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ground state

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group

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a vertical column on the periodic table

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halide

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a salt that includes a halogen

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halogen

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an element of Group 17

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heat

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energy transferred from one substance to another, measured in units of calories or joules

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heat of fusion

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the amount of heat need to convert a unit mass of a substance from a solid to a liquid at its melting point

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heat of vaporization

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the amount of heat needed to convert a unit mass of substance from a liquid to a vapor at its boiling point

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heterogenous

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a mixture in which the substances are not uniformly mixed

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homogenous

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a substance in which the particles are uniformly mixed

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inert gas group

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name of the Group 18 Noble Gases

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insoluble

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material with a low solubility

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ionization energy

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the amount of energy needed to remove the most loosely bound electron

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isotope

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atom of an element that has a different amount of neutrons

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kinetic molecular theory (theory used to explain behavior of gases in terms of their particle motion)

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- Gases contain particles that are in constant, random, straight-line motion

- They collide with each there and with the walls of the container. Transfer of energy occurs but not net loss of energy (perfectly elastic)

- They are separated by relatively great distances

- They do not attract each other

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law of conservation of mass

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matter is neither created nor destroyed in chemical reactions

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law of definite proportions

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types of atoms in a compound exist in a fixed ratio

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liquid phase

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a phase of matter having definite volume but no definite shape

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malleability

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the property of metals that allows them to be hammered into shapes

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mass number

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the total number of protons and neutrons in the nucleus of an atom

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matter

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anything that has mass and volume

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melting point

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the temperature at which both the solid and liquid phases exist in equilibrium; the same temperature as the substance's freeing point

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metal

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elect whose atoms lose electron in chemical reaction to become positive ions

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metalloid

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an element that has both metallic and nonmetallic properties

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molarity

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the concentration of a substance in moles per liter of solution : M = # of moles/ # liters of solution

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mole

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a number equal to an substance's total formula mass

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molecular formula

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the actual ratio of the atoms in a molecule

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neutron

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the uncharged particle in the nucleus of an atom

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noble gas

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a nonreactive element that is in group 18 on the periodic table

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nonmetal

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element whose atoms will tend to gain or share electrons in chemical reactions

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nucleus

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the dense, positively charged central core of an atom

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octet of elctrons

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the stable valence electron configuration of eight electrons

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orbital

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a region in an atom which an electron of a particular around of energy is most likely to be located.

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oxidation

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the loss of electrons and an increase in the oxidation state

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parts per million

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the ratio between the parts of solute per million parts of solution: ppm = mass of solute/mass of solution x 1,000,000

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percent by volume

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volume of solute/volume of solution x 100

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percent mass

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percent mass = mass of part/mass of whole x 100

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percentage composition

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find atomic masses and divide the requested mass by the total formula mass

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period

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a horizontal row of the periodic table

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periodic law

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the properties of elements are periodic function of their atomic numbers

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polyatomic ion

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a covalently bonded group of atoms that have a net electric charge

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proton

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the positively charged particle in the nucleus of an atom (weighs 1amu)

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quantum number

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one of a set of four numbers the describes a property of an electron in an atom

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quantum theory

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a concept that relates the chemical behavior of atoms to energy being transferred

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saturated

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a solution contain the maximum amount of solute that will dissolve at a given temperature

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solubility

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a measure of how much solute will dissolve in a certain amount of solvent at a specific temperature

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soluble

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material with a high solubility

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solute

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the substance being dissolved

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solution

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a homogenous mixture of substances in the same physical state

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solvent

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the substance that dissolves the solue

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sublimation

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the process in which a solid changes directly into a gas

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supersaturated

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a solution that contains more solute than would dissolve in a saturated solution at a given temperature

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synthesis

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a reaction in which two or more substances combine to form one product

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temperature

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the measure of the average kinetic energy of substance's particles

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unsaturated

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a solution in which more solute can be dissolved at a given temperature

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valence electrons

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the electrons in the outer energy level of an atom

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vapor

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the gaseous state of substance that is normally a liquid at temperature

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vapor pressure

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the pressure that a vapor exerts

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vaporization

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the constant temperature process in which particles in the liquid phase gain enough energy to break away into the gaseous phase (boiling)