Chapter 2 Definitions

Question 1

subatomic particles

Answer 1

the neutrons, protons, and electrons in an atom.

Question 2

cathode rays

Answer 2

streams of electrons emitted by the cathode in a partially evacuated tube.

Question 3

electron

Answer 3

a subatomic particle that has a relative charge of 12 and negligible mass.

Question 4

radioactivity

Answer 4

the spontaneous emission of high-energy radiation and particles by materials.

Question 5

beta (𝛃) particle

Answer 5

a radioactive emission that is a high-energy electron.

Question 6

alpha (𝛂) particle

Answer 6

a radioactive emission with a charge of 21 and a mass equivalent to that of a helium nucleus.

Question 7

nucleus (of an atom)

Answer 7

the positively charged center of an atom that contains nearly all the atom’s mass.

Question 8

proton

Answer 8

a subatomic particle in the nuclei of atoms that has a relative charge of 11 and a mass number of 1.

Question 9

neutron

Answer 9

an electrically neutral (uncharged) subatomic particle with a mass number of 1.

Question 10

atomic mass unit (amu)

Answer 10

the unit used to express the relative masses of atoms and subatomic particles that is exactly 1/12 the mass of 1 atom of carbon with 6 protons and 6 neutrons in its nucleus.

Question 11

dalton (Da)

Answer 11

a unit of mass equal to 1 atomic mass unit.

Question 12

isotopes

Answer 12

atoms of an element containing the same number of protons but different numbers of neutrons.

Question 13

nuclide

Answer 13

a specific isotope of an element.

Question 14

atomic number (Z)

Answer 14

the number of protons in the nucleus of an atom.

Question 15

nucleon

Answer 15

a proton or neutron in a nucleus.

Question 16

mass number (A)

Answer 16

the number of nucleons in an atom.

Question 17

cation

Answer 17

a positively charged ion.

Question 18

anion

Answer 18

a negatively charged ion.

Question 19

radionuclide

Answer 19

a radioactive (unstable) nuclide.

Question 20

halogen

Answer 20

from green word for “salt former.”

an element in group 17 of the periodic table.

Question 21

alkali metal

Answer 21

an element in group 1 of the periodic table.

Question 22

alkaline earth metal

Answer 22

an element in group 2 of the periodic table.

Question 23

chalcogen

Answer 23

an element in group 16 of the periodic table.

Question 24

metals

Answer 24

elements that are typically shiny, malleable, ductile solids that conduct heat and electricity well and tend to form positive ions.

Question 25

nonmetals

Answer 25

elements with properties opposite those of metals, including poor conductivity of heat and electricity.

Question 26

metalloids or semimetals

Answer 26

elements that tend to have the physical properties of metals and the chemical properties of nonmetals.

Question 27

main group elements or representative elements

Answer 27

the elements in groups 1, 2, and 13 through 18 of the periodic table.

Question 28

transition metals

Answer 28

the elements in groups 3 through 12 of the periodic table.

Question 29

noble gases

Answer 29

the elements in group 18 of the periodic table.

Question 30

molecular mass

Answer 30

the mass in amu of one molecule of a molecular compound.

Question 31

formula unit

Answer 31

the smallest electrically neutral unit of an ionic compound.

Question 32

formula mass

Answer 32

the mass in amu of one formula unit of an ionic compound.

Question 33

mole (mol)

Answer 33

an amount of a substance that contains Avogadro’s number of particles (atoms, ions, molecules, or formula units).

Question 34

Avogadro’s number (NA)

Answer 34

the number of carbon atoms in exactly 12 grams of carbon-12; (6.0221x10^23). It is the number of particles in 1 mole.

Question 35

molar mass (ℳ)

Answer 35

the mass of 1 mole of a substance.