Chapter 2: Atoms and Elements

Question 1

atomos

Answer 1

indivisible

Question 2

atomic theory

Answer 2

all matter is composed of atoms

Question 3

law of conservation of mass

Answer 3

in a chemical reaction, matter is neither created nor destroyed
- consistent with the idea that matter is composed of small, indestructible particles
when a chemical reaction occurs, the total mass of the substances involved in the reaction does not change

Question 4

law of definite proportions (law of constant composition)

Answer 4

all samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements

Question 5

law of multiple proportions

Answer 5

when two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers
- an atom of A combines with either one, two, three, or more atoms of B
- the ratio of these two masses is itself a small whole number

Question 6

Dalton’s atomic theory

Answer 6

• each element is composed of tiny, indestructible particles called atoms
• all atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements
• atoms combine in simple, whole-number ratios to form compounds
• atoms of one element cannot change into atoms of another element. in a chemical reaction, atoms only change the way they they are bound together with other atoms

Question 7

J.J. Thomson

Answer 7

proposed that the negatively charged electrons were small particles held within a positively charged sphere
- incorrect plum-pudding model

Question 8

nuclear theory

Answer 8

• most of the atom’s mass and all of its positive charge are contained in a small core called a nucleus
• most of the volume of the atom is empty space, throughout which tiny, negatively charge electrons are dispersed
• there are as many negatively charged electrons outside the nucleus as there are positively charged particles (named protons) within the nucleus, so that the atom is electrically neutral

Question 9

neutrons

Answer 9

neutral particles within the nucleus

Question 10

subatomic particles

Answer 10

protons, neutrons, electrons

Question 11

proton

Answer 11

charge = +1

Question 12

neutron

Answer 12

charge = 0

Question 13

electron

Answer 13

charge = -1

Question 14

atomic number

Answer 14

the number of protons in an atom’s nucleus

Question 15

chemical symbol

Answer 15

either a one- or two-letter abbreviation listed directly below its atomic number on the periodic table

Question 16

isotopes

Answer 16

atoms with the same number of protons but a different number of neutrons

Question 17

natural abundance

Answer 17

the percentages representing the relative amount of each different isotope in a naturally occurring sample of a given element is roughly constant

Question 18

mass number

Answer 18

the sum of the number of neutrons and protons in an atom

Question 19

ions

Answer 19

in chemical changes, atoms can lose or gain electrons and become charged particles called ____

Question 20

cations

Answer 20

positively charged ions, such as Na+

Question 21

anions

Answer 21

negatively charged ions, such as F-

Question 22

periodic law

Answer 22

when the elements are arranged in order of increasing mass, certain sets of properties recur periodically

Question 23

metals

Answer 23

lie on the lower left side and middle of the periodic table and share some common properties:
- good conductors of heat and electricity
- can be pounded into flat sheets (malleability)
- can be drawn into wires (ductility)
- often shiny
- tend to lose electrons when they undergo chemical changes

Chromium, copper, strontium, lead, etc.

Question 24

nonmetals

Answer 24

lie on the upper right side of the periodic table
- total of 17
properties:
- poor conductors of heat and electricity
- not ductile and not malleable
- gain electrons when they undergo chemical changes

Oxygen, carbon, sulfur, bromine, iodine, etc.

Question 25

metalloids/semimetals

Answer 25

• elements that lie along the zigzag diagonal line that divides metals and nonmetals
• exhibit mixed properties
• several are also classified as semiconductors because of their intermediate (and highly temperature-dependent) electrical conductivity

Question 26

main-group elements

Answer 26

properties tend to be largely predictable based on their position in the periodic table

Question 27

transition elements (transition metals)

Answer 27

properties tend to be less predictable based simply on their position in the periodic table

Question 28

group/family

Answer 28

each vertical column of the periodic table

Question 29

period

Answer 29

each horizontal row of the periodic table

Question 30

noble gases

Answer 30

the group 8A elements that are mostly unreactive
- Helium is chemically stable - it does not combine with other elements to form compounds - and is therefore safe to put into balloons
- others include neon (often used in electronic signs), argon (a small component of our atmosphere), krypton, and xenon

Question 31

alkali metals

Answer 31

the group 1A elements that are all reactive metals
- sodium, lithium, potassium, and rubidium
– have a tendency to lose one electron and form 1+ ions

Question 32

alkaline earth metals

Answer 32

the group 2A elements that are fairly reactive, but not quite as reactive as the alkali metals
- calcium, magnesium, strontium, and barium
– tend to lose two electrons and form 2+ ions

Question 33

halogens

Answer 33

the group 7A elements that are very reactive nonmetals and always found in nature as a salt
- chlorine, bromine, iodine, and fluorine
– tend to gain one electron and form 1- ions

Question 34

oxygen family nonmetals

Answer 34

group 6A elements that tend to gain two electrons and form 2- ions

Question 35

mole (mol)

Answer 35

the measure of material containing 6.02214x10^23 particles:
- 1 mole = 6.02214 x 10^23 particles

Question 36

Avogadro’s number

Answer 36

6.02214x10^23 particles

Question 37

molar mass

Answer 37

the mass of 1 mol of atoms of an element