Isotopes & Atomic Mass

Question 1

How is a symbol for a specific isotope of any element written?

Answer 1

By placing the mass number as a superscript to the left of the element symbol

Question 2

True or False: Since the atomic number defines the element’s identity, it is often omitted

Answer 2

True

Question 3

Is the density of solid water less than the density of liquid water?

Answer 3

Yes

Question 4

True or False: Each proton and neutron contribute 1 amu to the mass of an atom

Answer 4

True

Question 5

What is the atomic mass of a single atom approximately equal to?

Answer 5

The atomic mass of a single atom is approximately equal to its mass number (a whole number)

Question 6

True or False: The average masses of atoms of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes

Answer 6

True

Question 7

True or False: The mass of an element shown in a periodic table/listed in table of atomic masses is a weighted average mass of all the isotopes present in a naturally occurring sample of that element

Answer 7

True

Question 8

How can we find the mass of an element shown in the periodic table for all of the isotopes present?

Answer 8

The mass is equal to the sum of each individual isotope’s mass multiplied by its fractional abundance
(∑i (fractional abundance × isotopic mass)i)

Question 9

What can a mass spectrometer be used for?

Answer 9

The occurrence and natural abundance of isotopes through experimental determination

Question 10

What is the process of the hard ionization mass spectrometer?

Answer 10

Sample is vaporized and exposed to high-energy plasma that causes any chemical bonds to be broken and the constituent atoms to become electrically charged (by losing one or more electrons) which pass through electric/magnetic fields that detects atoms with only slight differences in mass (isotopes) while measuring their relative abundance

Question 11

What does a mass spectra of elements reveal?

Answer 11

The isotopic composition of the elements

Question 12

What occurs in a hard ionization mass spectrometer?

Answer 12

The sample is ionized by a high temperature plasma that breaks any bonds between atoms and causes them to lose electrons to make atomic cations

Question 13

What is the main difference between a hard-ionization mass spectrometer and a soft-ionization mass spectrometer?

Answer 13

Soft-ionization mass spectrometer does not break the covalent bonds of a molecule (therefore forming molecular ions)

Question 14

What occurs in a soft ionization mass spectrometer?

Answer 14

Molecular ions are deflected (depending on mass to charge ratio) as they fly through the mass spectrometer resulting in the mass spectrum telling us the molecular weight of the whole compound and its relative abundance

Question 15

What is a result when a molecule is subjected to hard ionization?

Answer 15

All covalent bonds are broken to produce monatomic ions

Question 16

What is a result when a molecule is subjected to soft ionization?

Answer 16

There is not a break in the covalent bonds of the molecule keeping the molecule intact and allowing us to know the molecular weight of the whole compound (x) and relative abundance (y)

Question 17

What information does hard ionization mass spectrum provide us?

Answer 17

Provides us with information about the individual atoms present in the sample

Question 18

What information does soft ionization mass spectrum provide us?

Answer 18

Provides us with information about the molecule itself

Question 19

What are isotopes of an element?

Answer 19

Atmos with the same atomic number but different mass numbers, differing only with the number of neutrons within the nucleus

Question 20

True or False: We can use hard ionization to break apart the molecule and determine the identity of the constituent atoms

Answer 20

True

Question 21

True or False: We can use soft ionization to determine the molecular mass of a molecule