1.2 Atomic Mass Vs Atomic Weight

Question 1

What are the different terms used to describe the heaviness of an element?

Answer 1

Atomic mass and atomic number (which are essentially synonymous) and atomic weight.

Question 2

While atomic weight is a constant for a given element and is reported in the periodic table, the atomic mass or mass number

Answer 2

Varies from one isotope to another

Question 3

The mass of one proton is approximately

Answer 3

One amu

Question 4

Atomic number (Z)

Answer 4

Number of protons

Question 5

Mass number (A)

Answer 5

Number of protons + number of neutrons

Question 6

Number of protons

Answer 6

Number of electrons (in a neutral atom)

Question 7

Electrons are not included in mass calculations because

Answer 7

They are much smaller

Question 8

The atomic number of an atom (in amu) is nearly equal to its

Answer 8

Mass number

Question 9

Atoms of the same element with varying mass numbers are called

Answer 9

Isotopes

Question 10

Isotopes mean

Answer 10

Same place

Question 11

Isotopes differ in their number of neutrons and are referred to by

Answer 11

the name of the element followed by the mass number (ex: carbon-12, iodine-131)

Question 12

What are the three isotopes of hydrogen?

Answer 12

Protium, deuterium, and tritium

Question 13

Protium

Answer 13

Greek: “first”, has one proton and an atomic mass of 1 amu

Question 14

Deuterium

Answer 14

Greek: “second”, has one proton and one neutron and an atomic mass of 2 amu

Question 15

Tritium

Answer 15

Greek: “third”, has one proton and two neutrons and an atomic mass of 3 amu.

Question 16

Because isotopes have the same number of protons and electrons

Answer 16

They generally exhibit similar chemical properties

Question 17

In nature, almost all elements exists as

Answer 17

Two or more isotopes, and these isotopes are usually present in the same proportions in any sample of a naturally occurring element

Question 18

The weighted average of these different isotopes is referred to as the

Answer 18

Atomic weight and is the number reported on the periodic table. For example chlorine has two main naturally occurring isotopes: chlorine-35 and chlorine-37; therefore, the atomic weight of chlorine is closer to 35 then 37. On the periodic table it is listed as 35.5.

Question 19

Half life corresponds with

Answer 19

Stability, it also helps determine the relative proportions of these different isotopes

Question 20

When an element has two or more isotopes

Answer 20

No one isotope will have a mass exactly equal to the elements atomic weight. Bromine, for example, is listed in the periodic table as having a mass of 79.9 amu. This is an average of the two naturally occurring isotopes, bromine-79 and bromine-81, which occur in almost equal proportions. There are no bromine atoms with an actual mass of 79.9 amu.

Question 21

The utility of the atomic weight is that it represents both

Answer 21

The mass of the “average” atom of that element, in amu, and the mass of one mole of the element, in grams

Question 22

A mole is a number of

Answer 22

“Things” (atoms, ions molecules) equal to Avogadro’s number NA=6.02 x 10^23

For example, the atomic weight of carbon is 12.0 amu, which means that the average carbon atom has a mass of 12.0 amu (carbon-12 is far more abundant than carbon-13 or carbon-14) , and 6.02 x 10^23 carbon atoms have a combined mass of 12.0 grams

Question 23

Atomic mass is nearly synonymous with

Answer 23

Mass number

Question 24

Atomic weight is a weighted average of

Answer 24

Naturally occurring isotopes of that element