Isotopes + Atomic Mass

Question 1

What are isotopes?

Answer 1

atoms wt the same number of protons but different number of neutrons

same element due to same number of protons

diff. mass # & weight due to diff. # of neutrons

Question 2

What are different representations of isotopes?

Answer 2

wt number of (protons + neutrons) & neutrons = nucleus symbol notation

wt number of protons = mass number

word form wt number of protons = word form

Question 3

What is mass number?

Answer 3

number of protons and electrons in an atom

whole # value

Question 4

What is relative atomic mass (Ar)?

Answer 4

weighted average of all the isotopes of an element, which takes into account the percentage abundance of each isotope (as it occurs in nature)

not whole # value

Question 5

How is relative atomic mass calculated?

Answer 5

((mass # x % abundance of isotope 1) + (mass # x % abundance of isotope 2)) / 100

Question 6

What is a mass spectrometer?

Answer 6

produces a spectrum (graph) used to identify isotopes / composition of unknown object

Question 7

What is percentage abundance?

Answer 7

how much of an isotope is present in nature

Question 8

What is atomic mass unit?

Answer 8

based on carbon -112 isotope

units - amu (atomic mass unit)

1 amu = 1/12 the mass of carbon 12

Question 9

What is atomic mass?

Answer 9

the mass of an atom of an atom based on the number of protons & neutrons in the nucleus, expressed in atomic mass units

whole #

Question 10

What is relative molecular mass (Mr)?

Answer 10

the sum of all relative atomic masses of each atom within a molecule (covalent substance)

Question 11

What is relative formula mass (Fr)?

Answer 11

the sum of the relative atomic masses of each atom within a formula unit (ionic compound)

ONLY GIVES MASS OF SMALLEST REPEATING UNIT