Physics Chapter 2 Vocabulary

Front 1

Greek atom

Back 1

Scientist thought matter was composed of four substances earth, water, air and fire.

Front 2

Atom

Back 2

The smallest particle that has all the properties of an element.

Front 3

Quantum chromodynamics (QCD)

Back 3

A newer model that shows the details of atomic structure more accurately.

Front 4

The fundamental particles of an atom

Back 4

The electron, the proton, and the neutron.

Front 5

Atomic mass unit (amu)

Back 5

Unit used to determine the atomic mass.

Front 6

Nucleons

Back 6

They are protons and neutrons.

Front 7

The chemical element

Back 7

Is determined by the number of protons.

Front 8

Ionized

Back 8

If an atom has an extra electron or has had an electron removed.

Front 9

Ionization

Back 9

Ionization is the process of adding or removing an electron from an atom.

Front 10

centripetal force

Back 10

The force that keeps an electron in orbit is the centripetal force.

Front 11

centrifugal force

Back 11

In the normal atom, the centripetal force just balances the force created by the electron velocity, the centrifugal force or flying-out-from-the-center force, so that electrons maintain their distance from the nucleus while traveling in a circular or elliptical path.

Front 12

Electron Binding Energy

Back 12

The strength of attachment of an electron to the nucleus is called the electron binding energy, designated Eb.

The binding energy of an electron is defined as that amount of energy needed to remove the electron from the atom.

Front 13

ionization potential

Back 13

Approximately 34 eV is necessary to ionize tissue atoms.

The value 34 eV is called the ionization potential.

Front 14

chemical symbols

Back 14

Often an element is indicated by an alphabetic abbreviation. Such abbreviations are called chemical symbols.

Front 15

Symbol "Z"

Back 15

The number of protons is called the atomic number, represented by Z.

Front 16

Symbol "A"

Back 16

The number of protons plus the number of neutrons in the nucleus of an atom is called the atomic mass number, symbolized by A.

Front 17

atomic mass

Back 17

The atomic mass number and the precise mass of an atom are not equal. The number of protons plus the number of neutrons in the nucleus of an atom is called the atomic mass number.

Front 18

elemental mass

Back 18

The characteristic mass of an element, the elemental mass, is determined by the relative abundance of isotopes and their respective atomic masses.

Front 19

Isotopes

Back 19

Atoms that have the same atomic number but different atomic mass numbers are isotopes. Isotopes of a given element contain the same number of protons but varying numbers of neutrons.

Front 20

Isobar

Back 20

Atomic nuclei that have the same atomic mass number but different atomic numbers are isobars. Isobars are atoms that have different numbers of protons and different numbers of neutrons but the same total number of nucleons.

Front 21

Isotone

Back 21

Atoms that have the same number of neutrons but different numbers of protons are isotones.

Isotones are atoms with different atomic numbers and different mass numbers but a constant value for the quantity A–Z.

Front 22

Isomer

Back 22

Isomers have the same atomic number and the same atomic mass number.

Isomers are identical atoms except that they exist at different energy states because of differences in nucleon arrangement.

Front 23

Molecule

Back 23

Atoms of various elements may combine to form structures called molecules.

When two or more atoms are chemically united, they form a molecule, which is the smallest particle of a compound that still possesses the characteristics of the compound.

Front 24

Compound

Back 24

A chemical compound is any quantity of one type of molecule.

A combination of elements bonded together.

Front 25

covalent bonds

Back 25

Covalent bonding is characterized by the sharing of electrons.

Front 26

ionic bonds

Back 26

The two atoms are attracted to each other, resulting in an ionic bond because they have opposite electrostatic charges.

Front 27

Radioactivity

Back 27

Radioactivity is the spontaneous emission of particles and energy in order to become stable.

This process is called radioactive disintegration or radioactive decay.

Front 28

radioisotopes

Back 28

In addition to stable isotopes, many elements have radioactive isotopes or radioisotopes.

Front 29

Radioactive decay

Back 29

Radioactive decay results in emission of alpha particles, beta particles, and usually gamma rays.

Front 30

Radioactive Half-life

Back 30

The half-life of a radioisotope is the time required for a quantity of radioactivity to be reduced to one-half its original value.

Theoretically, all the radioactivity of a radioisotope never disappears.

Front 31

Radioactive Decay

Back 31

Activity remaining = Original activity (0.5)n

where n = number of half-lives.

Naturally occurring process whereby an unstable Atomic nucleus relieves is instability through the emission of one or more energetic particles.

Front 32

Types of Ionizing Radiation

Back 32

All ionizing radiation can be conveniently classified into two categories:

particulate radiation and electromagnetic radiation.

Front 33

Particulate Radiation

Back 33

There are two main types of particulate radiation: alpha particles and beta particles. Both are associated with radioactive decay.

Particulate form of ionizing radiation that consists of two protons and two neutrons, nucleus of helium emitted from the nucleus of a radioactive atom.

Radiation distinct from X-rays and gamma rays, examples include alpha particles, electrons, neutrons, and protons.

Front 34

Alpha Particle

Back 34

An alpha particle is a helium nucleus that contains two protons and two neutrons. No electrons.

Front 35

Beta Particle

Back 35

A beta particle is an electron emitted from the nucleus of a radioactive atom.

Front 36

Electromagnetic Radiation

Back 36

X-rays and gamma rays are forms of electromagnetic ionizing radiation. Gamma rays come from the nucleus. X-rays come from the electron cloud.

Front 37

Ion

Back 37

If an atom gains or loses an electron, it is called an ion.

Front 38

Electron volt (eV)

Back 38

The binding energy of an electron is measured in a unit called the electron volt (eV)

Front 39

Mechanical energy

Back 39

Mechanical energy mechanical energy is the result of the action of machines or physical movement.

There are two types of mechanical energy: potential and kinetic.

Front 40

Ion pair

Back 40

When a positively charged particle (positive ion) and the negatively charged particle (negative ion) simultaneously produced by the addition of sufficient energy to a neutral atom or molecule to cause it to disassociate and two oppositely charged fragments.

Front 41

Binding energy

Back 41

The energy that holds protons and neutrons together in the nucleus through the force of attraction. The amount of energy needed to break up the nucleus.

Front 42

Electromagnetic energy

Back 42

Pure Energy, rather than particles with Mass.

The term is used because rays of electromagnetic energy have properties of both electrical energy and magnetic energy.

Electromagnetic energy travels at the speed of light.

Front 43

Element

Back 43

The simplest form of a substance that composes matter.

Each element has only one unique type of atom in it, with a set number of protons.

There are ninety two elements existing in the natural world, and other elements have been created artificially.

Front 44

Fundamental particle

Back 44

A basic component of an atom, including the electron, Neutron, and proton.

Front 45

Half life

Back 45

The length of time it takes for half the atoms in a certain amount of an element to decay, the unit used to measure radioactivity.

Front 46

Radioactive decay

Back 46

The process by which radionuclides (radioactive atoms) emit particles and energy.

Front 47

Radioactive element

Back 47

An element composed of atoms with unstable nuclei that radiates particles and energy.

Front 48

Radioactivity

Back 48

A general term for the processes by which atoms with unstable nuclei radiate excess energy in the form of particles and energy.

Front 49

Radionuclides

Back 49

A radioactive atom

Front 50

Strong nuclear force

Back 50

The force of attraction between all the particles of a nucleus, both protons and neutrons.

Front 51

Electromagnetic energy

Back 51

Can be transformed from one size, shape, and form to another

Front 52

Thermal energy (heat)

Back 52

The energy of motion at the molecular level

Front 53

Power

Back 53

The rate of doing work

Front 54

Thermal radiation

Back 54

Transfer of heat by the emission of infrared radiation

Front 55

Air kerma

Back 55

The unit of radiation exposure or intensity

Front 56

Radioactive decay

Back 56

Natural process whereby an unstable Atomic nucleus relieves its instability through emission of energetic particles

Front 57

Molecule

Back 57

Smallest unit of a compound that can exist by itself and retain all its chemical properties

Front 58

Radioisotopes

Back 58

Radioactive atoms that have the same number of protons

Front 59

Radioactive half-life

Back 59

Time required for a quantity of radioactivity to be reduced to one half its original value

Front 60

Shells

Back 60

Electron binding Energies

Front 61

Electromagnetic radiation

Back 61

Oscillating electric and magnetic fields that travel in a vacuum with the velocity of light

Front 62

Molecule

Back 62

Group of atoms of various elements held together by chemical forces

Front 63

Electron

Back 63

Surrounds positively charged nucleus; determines chemical properties of the atom

Front 64

Particulate radiation

Back 64

Radiation distinct from X-rays and gamma rays

Front 65

Radioactive decay

Back 65

Results in emission of alpha particles, beta particles, and usually gamma rays