Academic Decathlon - Chemistry 2022-2023

Scientific Revolution

a term often used to describe the emergence of modern science during the sixteenth and seventeenth centuries; much current scholarship questions the concept of a Scientific Revolution.

practice that was particularly popular during the Middle Ages that focused on trying to change other metals into gold or silver.

Alchemy

the process of relying on experiments and observations in the natural sciences

Empiricism

the simplest type of substance with unique physical and chemical properties

Elements

a charged particle formed when an atom either gives up one or more electrons or gains one or more electrons

Ion

the average mass of an atom of an element; it is the weighted average of the isotopes based on the proportion of each isotope in a given element sample.

Atomic mass

an instrument used to measure the relative masses of ions

mass spectrometers

the idea that matter is made up of fundamental particles called atoms

Atomic theory of matter

state of matter characterized by molecules being spread out from each other and therefore highly compressible; takes the shape of any container it is in, creating uniform pressure in all directions

gas

English chemist and physicist who formulated atomic theory and the law of partial pressures

John Dalton

first to propose that matter was composed of small, indestructible particles or atoms

Leucippus and Democritus

measure of how hot or cold a substance is relative to another substance; a measure of the thermal (motion) energy content of a system

temperature

a law stating that the total pressure of a mixture of gases is the sum of the pressures of the individual gases in the mixture

law of partial pressures

the starting substances in a chemical reaction

reactants

the substances that are formed in a chemical reaction

products

of the same proportion of each element.

Proust's law of definite proportions

mass law that states if two elements react to form more than one compound, the masses of one element will combine with the other element in a whole number ratio

Law of Multiple Proportions

Published in 1808 by John Dalton; included Dalton's basic atomic principles

A New System of Chemical Philosophy

the very dense positively charged center part of the atom that contains the protons and neutrons and, consequently, most of the mass of the atom

nucleus

fundamental particle of matter that has a negative charge; discovered by J. J. Thompson in 1896

electrons

a discrete unit or quantum of electromagnetic radiation; forms include microwaves, light waves, X rays, and gamma rays; photons are emitted when electrons move from one energy state to another in an atom, for example, when an excited electron drops from the sixth energy level to the second energy level; the energy released to make the change is the energy of the emitted photon.

proton

a fundamental particle of matter found in the nucleus that has a mass of 1.009 amu but no electric charge; first identified by Sir James Chadwick in 1932

neutrons

the number of protons in the nucleus of an atom; this identifies the type of atom; for example, all atoms with seven protons are nitrogen.

atomic number

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

mass number

an alternate form of the same element that has a different mass number due to its having a different number of neutrons

isotope

a nuclear species of an atom characterized by mass (protons + neutrons), charge (protons), and energy content

nuclide

an atom whose nucleus will break up to form a more stable arrangement of the nuclear particles; natural or artificial transmutation was first discovered by Antoine Henri Becquerel in 1896; radioactivity is not affected by the chemical state of the atom, and thus processes like burning do not destroy an atom's radioactivity.

radioactive atoms

Abbreviated amu and also called a Dalton, it is the mass equal to 1/12 the mass of a carbon-12 atom.

atomic mass units

An isotope of hydrogen with one proton and one neutron in the nucleus having an atomic weight of 2.014

Deuterium

radioactive carbon

C-14

a metal alloy made with primarily iron and carbon whose composition varies; other components can include nickel, chromium, cobalt, molybdenum, or zirconium.

Steel

the smallest possible unit of energy; this unit can apply to any form of energy.

quantum

a discrete unit or quantum of electromagnetic radiation; forms include microwaves, light waves, X rays, and gamma rays; photons are emitted when electrons move from one energy state to another in an atom, for example, when an excited electron drops from the sixth energy level to the second energy level; the energy released to make the change is the energy of the emitted photon.

photon

the spectrum produced when atoms absorb specific wavelengths of incoming light and become excited from lower to higher energy levels; this pattern of absorption can be used in identifying an element.

absorption spectrum

the line spectrum produced when excited atoms return to lower energy levels and emit photons characteristic of the element; the pattern of emission can be used in identifying an element.

emission spectrum

a model of the atom where electrons orbit the nucleus like planets around the sun, but at predetermined distances; electrons can transition from one orbit to a different empty one.

Bohr model of the atom

a model of the atom that explains the presence of electrons as "stationary" waves in orbitals

quantum mechanical model

the emission of an electron from a metal's surface as a result of the absorption of a photon (electromagnetic radiation); this phenomenon was first explained by Albert Einstein; the amount of energy varies depending on the metal and the wavelength of the photon.

photoelectric effect

an experiment showing that electrons are scattered off crystals of nickel and interfere with each other - also know as "electron diffraction"

Davisson-Germer Experiment

Danish physicist whose model of the atom and how it absorbs and emits energy contributed to quantum theory and is also widely used in the teaching of elementary chemistry today.

Niels Bohr (1885-1962)

the representation of the areas occupied by electrons in the atom; the types of electron clouds include ones with different shapes called "orbitals."

electron "cloud

in an atom, the area in space around the nucleus where an electron is found; each orbital holds only one or two electrons.

orbital

A chart of the elements showing the repeating pattern of their properties

periodic table

column on the periodic table; for example, alkali metals (group 1) or noble gases (group 18)

groups

half the distance between two adjacent atoms in an element's crystal

Atomic radius

the amount of energy needed to remove a mole of electrons from a mole of atoms (one electron per atom) in the gaseous state; measured in kilojoules per mole

ionization energy

the energy change, in kJ, when one mole of atoms of an element adds a mole of electrons (one per atom)

Electron affinity

the ability of an atom to attract shared electrons in relative units

Electronegativity

bonds that occur between two oppositely charged ions

ionic bond

a molecule that contains at least two different elements that are chemically combined in a fixed ratio

compound

an attractive force that exists between two atoms such that the combination of atoms behaves as a unit that requires force (energy) to break apart

chemical bond

the sharing of a pair of electrons by two atoms in a chemical bond

covalent bonds

a compound consisting of two or more atoms held together by a chemical bond

molecule

force created by the attraction of oppositely charged ions or charged particles

electrostatic force

the force in a bond that holds the atoms within a molecule together

intramolecular

a type of bond that forms between metal atoms in a solid metal, where the atoms act as if positive ions form and electrons are mobile in a "sea" and so can conduct an electric charge

metallic bonds

written expression using symbols and subscripts to indicate the number and type of each atom in a chemical unit

chemical formula

the type of force that attracts one molecule to another molecule

intermolecular forces

a solid or liquid mixture of two or more metals; some common alloys include steel, brass, and bronze.

alloy

an alloy of primarily copper and zinc with varying proportions of each metal

Brass

weak forces of attraction between atoms or molecules that result from permanent or temporary electrostatic forces

van der Waals forces

a molecule with an unequal overall distribution of permanent positive and negative charge; such a molecule has a net dipole moment that is not equal to zero.

polar molecules

weak attraction that results from a polar molecule inducing a dipole in an atom or in a nonpolar molecule by disturbing electron arrangement of the nonpolar species

induced dipoles

a momentary induced dipole created when a polar molecule distorts the electron cloud of a nonpolar molecule

temporary dipoles

a molecule without a net permanent dipole

nonpolar molecules

a type of dipole-dipole force between molecules involving the attraction of a hydrogen, which is bound to one strongly electronegative atom, either a nitrogen, oxygen, or fluorine atom in another molecule; for example, the bond that occurs when the hydrogen in a water molecule is attracted to the nitrogen atom in an ammonia molecule.

Hydrogen bonds

A complex molecule containing the genetic information that makes up the chromosomes.

DNA

discovered the structure of DNA

James Watson and Francis Crick

British chemist and physicist who established that water is a compound of hydrogen and oxygen and who calculated the density of the earth (1731-1810)

Henry Cavendish

repeating pattern of positive and negative ions forming an ionic compound

Ionic lattice

an extended lattice formed of covalent bonds, such as in SiO2 or diamond

covalent network

Compounds with ionic bonds exist as lattice networks extending in three dimensions. Sodium chloride consists of a lattice of alternating Na+ and Cl- ions.

Sodium Chloride Lattice Structure

The structure of part of a DNA double helix.

A summary of intermolecular forces

A summary of intramolecular forces.

The Bohr model of the atom.

In the quantum mechanical model, the electrons are not at exact distances or fixed locations and do not rotate in orbits

The quantum mechanical model of the atom.

a gas law that states that equal
volumes of an ideal gas contain equal numbers of
particles at constant temperature and pressure and
thus the volume of a gas is directly proportional to
the number of moles of the gas

Avogadro's law

a solid held together by weak intermolecular forces between the molecules; typical molecular solids have relatively low melting points and boiling points.

molecular solids

one of several possible forms of an element; for instance, carbon can be graphite, diamond, or buckminsterfullerene (commonly called "buckyballs").

allotropes

any substance with a low thermal conductivity and/or low electrical conductivity

insulator

a unit cell of a crystal where there is a particle at each corner of a cube and one in the center

body-centered cubic

describes a crystal structure that has atoms at each corner of the cube and six atoms at each face of the cube

face-centered cubic

a crystal structure based on a hexagonal unit cell layering

close-packed hexagonal

refers to the appearance of a substance's surface in reflected light; metals have luster.

lustrous

producing sound

sonorous

a state of matter such as a solid, liquid, or gas

phase

describes the property of a substance indicating it can easily be flattened into thin sheets

malleable

the property of a metal that describes how easily the metal can be pulled into a wire without breaking

ductile

the condition of a chemical reaction when the forward rate and the reverse rate are equal, so there is no apparent change

Equilibrium

the endpoint of the liquid-gas curve on a phase diagram; it is the point at which a vapor and liquid become indistinguishable.

critical point

the one temperature and pressure at which all three phases of a substance (solid, liquid, and gas) exist at the same time in equilibrium with each other

triple point

the temperature at which a substance transitions from a solid to a liquid; usually measured at 1 atmosphere of pressure

melting point

the temperature at which the vapor pressure of a liquid substance equals the atmospheric pressure; normal boiling points are defined at 1 atmosphere of pressure.

boiling point

• invented analytic balance

• discovery of fixed air ( CARBON DIOXIDE) by pouring acid on chalk and capturing the bubbles (heavier than air)

Joseph Black (1728-1799)

the process of being surrounded by water solvent molecules; this process can also form solid crystals called hydrates.

hydration

capable of being dissolved

soluble

incapable of being dissolved

Insoluble

a mixture in which the composition is uniform throughout

homogenous mixture (solution)

A liquid substance capable of dissolving other substances

Solvent