Chapter 2: Atoms and the Periodic Table

Question 1

Dalton’s Atomic Theory

Answer 1

assumptions about atoms and matter to explain the chemical behavior of matter:
all matter is composed of atoms
all atoms of a given element are identical
the atoms of a given element are different from the atoms of all other elements
chemical compounds consist of atoms combined in specific ratios
chemical reactions change only the way that atoms are combined in compounds; the atoms themselves are unchanged

Question 2

law of constant composition

Answer 2

a given compound always contains the same proportions (by mass) of the elements

Question 3

atom

Answer 3

the smallest and simplest particle of an element

Question 4

atomic mass unit (amu)

Answer 4

a unit for describing the mass of an atom

Question 5

nucleus

Answer 5

the dense, central core of an atom that contains protons and neutrons

Question 6

atomic number (Z)

Answer 6

the number of protons and electrons in atoms of a given element

Question 7

mass number (A)

Answer 7

the total number of protons and neutrons in an atom

Question 8

isotopes

Answer 8

atoms with identical atomic numbers but different mass numbers (different amounts of neutrons)

Question 9

atomic weight

Answer 9

the weighted average mass of an element’s atoms

Question 10

main group element

Answer 10

an element in the first two or last six columns

Question 11

transition metal element

Answer 11

an element in the middle ten columns

Question 12

inner transition metal element

Answer 12

an element in the fourteen columns beneath the table

Question 13

alkali metal

Answer 13

in group 1; shiny, soft metals; low melting points; react rapidly with water to produce alkaline (basic) products; never found pure in nature

Question 14

alkaline earth metal

Answer 14

in group two; lustrous, silvery metal; slightly reactive; never found pure in nature

Question 15

halogen

Answer 15

in group seventeen; colorful and corrosive nonmetals; only found combined with other elements in nature

Question 16

noble gas

Answer 16

in group eighteen; colorless; lack chemical reactivity

Question 17

shell

Answer 17

a grouping of electons in an atom according to energy

Question 18

subshell

Answer 18

a grouping of electrons in a shell according to the shape of the region of space they occupy

Question 19

orbital

Answer 19

a region of space within an atom where an electron in a given subshell can be found

Question 20

electron configuration

Answer 20

the specific arrangement of electrons in an atom’s shells and subshells

Question 21

valence shell

Answer 21

the outermost electron shell of an atom

Question 22

valence electron

Answer 22

an electron in the outermost shell; the most important in determining an element’s properties because they are the most loosely held

Question 23

electron-dot symbol

Answer 23

an atomic symbol with dots placed around it to indicate the number of valence electrons

Question 24

ground state

Answer 24

an atom with its electrons in their usual, lowest-energy location

Question 25

excited

Answer 25

an electron that receives energy and is promoted to a higher energy level

Question 26

cathode ray tube

Answer 26

invented by William Cookes; a tube where negatively charge particles emitted from the cathode (negative) and travel to the anode (positive)

Question 27

Cathode Ray Experiment

Answer 27

performed by J.J. Thomson; a positive magnet was placed outside a cathode ray tube and the negatively charged particles moved toward it; allowed the theory that the negative particles -electrons- were in every element

Question 28

Plum Pudding Model

Answer 28

William Thomson’s model of the atom; since an atom is neutral, there must be another charge to oppose the electrons; theorized an atom as positively charged space with negatively charged electrons placed throughout

Question 29

Radioactive Particle Experiment

Answer 29

radioactive particles were directed straight through two charged plates (one positive, one negative); the particles were shown on a photographic plate in three places, which led to the theory that there are three charges: positive, negative, and neutral; one particle moved more so also theorized that it was larger

Question 30

Gold Foil Experiment

Answer 30

performed by Ernest Rutherford; radioactive particles were directed through a gold foil; the particles flew through the foil with little to no change in their flight, but some were significantly moved; theorized that an atom contains a small, poistively charged center (called the nucleus) that must contain nearly all of the atom’s mass, but only a tiny fraction of space

Question 31

neutron

Answer 31

discovered by Chadwick

Question 32

Modern View of the Atomic Theory

Answer 32

through the scientific method, this theory was ammended to include only:
all matter is composed of atoms
the atoms of a given element from the atoms of other elements
chemical reactions change only the way that atoms are combined in compounds; the atoms themselves are unchanged

Question 33

wavelength

Answer 33

the distance between consecutive peaks or troughs for a series of waves

Question 34

frequency

Answer 34

the number of wavelengths that pass a particular point in space per second

Question 35

speed

Answer 35

how fast a series of waves moves through space

Question 36

photon

Answer 36

a tiny packet of energy

Question 37

line spectrum

Answer 37

light is emitted by atoms only at certain wavelengths that correspond to specific colors; each element has a unique set of these

Question 38

Bohr Model of the Atom

Answer 38

based on the hydrogen line spectrum; electrons exist in specific regions at various distances from the nucleus; there are many possible electron orbits around the nucleus, each of which correspond to a different energy; the farther the electron orbit is away from the nucleus, the higher its energy; quantized energy levels; leads ot the emission of photons

Question 39

quantized energy levels

Answer 39

specific energy levels for an electron to exist

Question 40

quantum mechanical model of an atom

Answer 40

theorized by Erwin Schrodinger; determined the probability of finding an electron in a certain area of space; description of location of electrons is now 3-D

Question 41

electron configuration

Answer 41

shows the exact arrangement of electrons

Question 42

electron dot symbol

Answer 42

valence electrons are represented as dots around the element symbol; simplifies the representation of transfer of electrons