Chapter 25

Question 1

Electrons

Answer 1

negatively charged subatomic particles

Question 2

Cathode ray

Answer 2

glowing beam that traveled from the cathode to the anode

Question 3

Protons

Answer 3

positively charged sub atomic particles. Each proton has a mass about 1840 times that of an electrom

Question 4

Neutrons

Answer 4

subatomic particles with no charge buth with a mass nearly equal to that of a proton.

Question 5

Nucleus

Answer 5

tiny central core of an atom and is composed of protons and neutrons

Question 6

Atomic number

Answer 6

number of protons in the nucleus of an atom of that element

Question 7

Mass Number

Answer 7

total number of protons and neutrons in an atom

Question 8

Isotopes

Answer 8

atoms that have the same number of protons but different numbers of neutrons

Question 9

Atomic mass unit (amu)

Answer 9

is defined at one twelfth of the mass of a carbon-12 atom

Question 10

atomic mass of an element

Answer 10

is a weighted average mass of the atoms in a naturally occurring sample of the element. A weighted mass reflects botht he mass and the relatibe abundance of the isotopes as they occur in nature.

Question 11

How do you calculate atomic mass of an element

Answer 11

multiply the mass of each isotope by its natural abundance, expressed as a decimal and then add the products.

Question 12

energy levels

Answer 12

the fixed energies an electron can have

Question 13

quantum of energy

Answer 13

the amount of energy required to move an electron from one energy level to another energy level

Question 14

quantum mechanical model

Answer 14

is the modern description of the electrons in atoms. determins the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus of an atom

Question 15

atomic orbital

Answer 15

describing the poabability of findinf an electron at various location around the nucleus

Question 16

electron configurations

Answer 16

the ways in which electrons are arranged in various orbitals around the nuclei of atoms

Question 17

aufbau principle

Answer 17

electrons occupy the orbitals of lowest energy first

Question 18

Pauli exclusion principle

Answer 18

an atomic orbital may describe at most two electrons

Question 19

Spin

Answer 19

a quantum mechanical property of. electrons and may be thought of as clockwise or counterclockwise

Question 20

Hund’s rule

Answer 20

electrons occupy orbitals of the same energy in a way that makes the number of electrons wiht the same spin directions as large as possible.

Question 21

Nuclear force

Answer 21

an attractive force that acts between all nuclear particles that are extremely close together, such as protons and neutrons in a nucleus

Question 22

Band of stability

Answer 22

a plot of neutrons vs. protons for all stable nuclei forms a pattern

Question 23

Positron

Answer 23

a particle withthe mass of an electron but a positive charge.

Question 24

Half-life

Answer 24

the time required for one-half of the nuclei in a radioisotope sample to decay to products.

Question 25

Transmutation

Answer 25

the conversion of an atom of one element into an atom of another element. Transmutation can occur by radioactive decay or when particles bombard the nuceul of an atom.

Question 26

Transuranium elements

Answer 26

elements with atomic numbers above 92, the atomic number of uranium

Question 27

Fission

Answer 27

when the nucei of certain isotopes are bombarded with neutrons, the nuclei split into smaller fragments

Question 28

Neutron moderation

Answer 28

a process that slows down neutrons so the reactor fuel can capture them to continue the chain reaction

Question 29

Neutron absorption

Answer 29

a process that decreases the number of slow-moving neutrons

Question 30

Fussion

Answer 30

occurs when nuclei combine to produce a nucleus of greater mass.

Question 31

ionizing radiation

Answer 31

the radiation emitted by radioisotopes

Question 32

Atom

Answer 32

the smallest particle of an element that retains its identity in a chemical reaction

Question 33

Daltons atomic theory

Answer 33

1. all elements are composed of tiny indivisible particles called atoms, 2. Atoms of the same element are identical. Atoms of any one element are different from those of any other element. 3. Atoms of different elements can physically mix together or can chemically combine in simple whole number ratios to form compounds. 4. Chemical reactions occur when atoms are separated from eachother, joined or rearranged in a different combination. Atoms of one element are never changed into the atoms of antoher element as a result of a chemical reaction.