Definitions Flashcards
Matter
Substance that has mass and takes up space.
Chemistry
The science of the materials that make up the universe-what they are made of, how they interact, and how they change.
Solid
A form of matter that has a definite shape and volume.
Liquid
A form of matter that does not have a definite shape but has a definite volume. A liquid conforms to the shape of its container.
Gas
A form of matter that has no definite shape, weight, or size. The volume (size) of a gas is related to its temperature and the pressure being placed on it by its environment.
Plasma
A hot gas whose matter is broken into charged particles. Plasma exists in areas of extreme heat, like the center of stars.
Element
A specific form of matter composed of only one type of atom. Elements cannot be divided into different types of matter. Elements are classified by the number of protons in an atom of that element.
Compound
Two or more elements combined chemically. The compound has different chemical properties than those of its individual elements, and it can only be separated by chemical means.
Mixture
Two or more elements that are combined physically rather than chemically. The individual elements retain their own chemical properties and can be separated by physical means.
Proton
One of the principal particles of an atom. The proton has a positive electrical charge, and is found in the nucleus of an atom. A proton weighs one atomic mass unit.
Neutron
One of the principal particles in an atom. The neutron has no electric charge, and is found in the nucleus of an atom. The mass of a neutron is about one atomic mass unit.
Electron
The smallest significant particle in an atom. Electrons have a negative charge and orbit around the nucleus.
Quark
A sub atomic particle that makes up protons and neutrons. Quarks are divided into “up” quarks, which have a charge of positive 2/3, and “down” quarks, which have a charge of negative 1/3. Protons are made up of two up quarks and one down quark, giving them a total charge of positive one. Neutrons are made of two down quarks and one up quark, giving them a total charge of zero.
Lepton
Family of particles (as electrons, muons, and neutrinos) that experience no strong forces.
Nucleus
The central core of an atom. The nucleus is made of protons and neutrons. The electrons circle around the nucleus.
Ion
A variation of an atom or atoms based on the loss or gain of an electron. This changes the charge of the atom.
Cation
An atom that has lost an electron. Cations have more protons than electrons, giving them a positive charge.
Anion
An atom that has gained an electron. Anions have more electrons than protons, giving them a negative charge.
Atomic mass
The total average number of protons and neutrons in an atom. A measurement of the mass of an atom can be estimated by calculating the total number of protons and neutrons in the atom’s nucleus. Atomic mass is measured in atomic units.
Atomic mass units (amu)
A unit of measurement for the mass (size or largeness) of an atom. One atomic mass unit is roughly equal to the mass of one proton, 1.66*10^-27 kg.
Periodic Table of Elements
A system of organization for the elements. Elements are positioned based on their atomic number and type. The Periodic Table lists information about each element, including atomic number, atomic mass, and symbol.
Atomic number
The number of protons contained in an atom. Each element has its own invariable atomic number. The atomic number is often used to identify elements.
Period
The name for a row in The Periodic Table of Elements. Periods are determined by the highest energy level where electrons can be found in an atom. Elements found in the lower periods of the Periodic Table have much higher energy than those found in the upper periods.
Group
The name for a column in the Periodic Table of elements. Groups are generally divided based on the number valence electrons in an atom of the element. In the United States, groups are numbered with Roman numerals and capital letters, e.g., I-VIIIA and I-VIIIB
Metal
In the Periodic Table of Elements, the most abundant of the three broad categories into which elements are classified based on their properties. Metals are good conductors of electricity and have a metallic sheen. They can be molded or stretched without breaking.
Nonmetal
In the Periodic Table of Elements, one of the three broad categories into which elements are classified based on their properties. Nonmetals, in a solid form, do not gleam, are poor conductors, and tend to be fragile.
Metalloid
In the Periodic Table of Elements, one of the three broad categories into which elements are classified based on their properties. Metalloids are also called semimetals, or semiconductors. Metalloids sometimes have the metallic gleam of metals, but are more fragile. They can conduct heat and electricity but not as well as metals.
Isotope
A variation of an element based on the number of neutrons in its nucleus.
Electron configuration
The organization of electrons around the nucleus of an atom. The electron configuration of an element is determined by the number of electrons it possesses and their position in the energy levels around the atom
Orbital
Another name for an energy level; a field that defines the pattern and position in which electrons move about the nucleus of an atom. The outermost orbitals give shape to the atom.
Energy level
A region surrounding the nucleus of an atom. Electrons move around the nucleus in energy levels. The location and behavior of electrons can be predicted based on these energy levels. Energy levels closer to the nucleus have lower energy than those farther away.
Electron cloud
A region around the nucleus in which electrons are predicted to be found at any given point. Electron cloud are sometimes represented as orbitals or energy levels. Electron clouds are used to approximate the location and behavior of electrons.
Valence electron
Valence electrons an electron in the outermost (usually incomplete) orbital of an atom. Every element has a unique number of valence electrons. Valence electrons determine how an element combines with other elements.
Molecule
A group of atoms linked by a chemical bond. A molecule is the smallest independent unit of a compound.
Covalent bond
A chemical bond between two (generally similar) elements. Covalent bonding occurs when one atom shares electron(s) with another atom, creating a bond between the two atoms as they both attract the shared electron(s).
Ionic bond
A chemical bond between two (generally dissimilar) elements. Ionic bonding occurs when one atom gives electron(s) to the other atom, making both atoms into ions that bond with each other.
Homonuclear diatomic
A molecule composed of two identical or the same type of atoms. H2 is an example.
Molecular mass
The combined masses of each atom in a molecule.
Mole
A group of atoms or molecules that total 6.022*10^23. The mole is a convenient conversion unit for chemistry calculations.
Lewis structures
Electron dot diagrams developed by Gilbert Newton Lewis in the early 1900s to illustrate valence electrons in elements. The structures are used to show the changes in electron orbital structures caused by chemical bonding.
