Average Atomic Mass

Multiple Choice

The properties of elements are periodic functions of their

• mass numbers

• atomic numbers

• atomic masses

• atomic radii

Multiple Choice

If an element has two isotopes with masses 10 amu and 12 amu, and their abundances are 25% and 75% respectively, what is the average atomic mass of the element?

• 13 amu

• 10.5 amu

• 11.5 amu

• 9 amu

Multiple Choice

If an element has two isotopes with masses 5 amu and 7 amu, and their abundances are 40% and 60% respectively, what is the average atomic mass of the element?

• 5.6

• 6.8

• 7.5

• 6.2

Multiple Choice

If an element has two isotopes with masses 8 amu and 10 amu, and their abundances are 60% and 40% respectively, what is the average atomic mass of the element?

• 8.8 amu

• 10.4 amu

• 9.6 amu

• 9.2 amu

Multiple Choice

If 75.0% of the isotopes of an element have a mass of 35.0 amu and 25.0% of the isotopes have a mass of 37.0 amu, what is the atomic mass of the element?

• 35.0 amu

• 35.5 amu

• 37.0 amu

• 36.0 amu

Multiple Choice

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
How many protons does this element have?

• 32
• 33
• 34
• no way to know

Multiple Choice

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
What is the average mass of this element?

• 74.92 amu
• 24.97 amu
• 75.01 amu
• 74.51 amu

Multiple Choice

An element has three different isotopes. One has a mass of 35.00 amu; another has a mass of 36.00  amu; and another has a mass of 38.00  amu. What is the average atomic mass of this element?

• 36.33 amu
• 37.00 amu
• 12.11 amu
• impossible to tell

Multiple Choice

An element with 4.35% have a mass of 49.9461 amu, 83.79% have amass of 51.9405 amu, 9.50% have a mass of 52.9407 amu, and 2.36% have a mass of 53.9389amu.

• 51.99 amu
• 52.19 amu
• 53.45 amu
• 17.33 amu

Multiple Choice

An isotope has three forms.  30% have a mass of 4 amu, 20% have a mass of 5 amu and 50% have a mass of 3 amu.  Average atomic mass will be closest to

• 2 amu
• 3 amu
• 4 amu
• 5 amu

Multiple Choice

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

Multiple Choice

If X is the symbol for an element, which of the following two symbols represent    isotopes of the same element?  
I. ⁷⁷₃₅X  II. ⁷⁷₃₃X  III. ⁸¹₃₇X  IV. ⁸¹₃₅ X

• I and II
• III and IV
• I and IV
• I and III

Multiple Choice

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

Multiple Choice

What is the name of the atom pictured here?

• Nitrogen
• Nitrogen-15
• Nitrogen-7
• Nitrogen-8

Multiple Choice

An element has three isotopes. Given the abundances and relative masses, calculate the average atomic mass and determine (from the periodic table) which element it is.

Abundances | Relative masses

0.005% | 234.04 amu

0.720% | 235.04 amu

99.275% | 238.05 amu

• Uranium (#92, Atomic Mass: 238.03 amu)

• Fluorine (#9, Atomic Mass: 19.00 amu)

• Mercury (#89, Atomic Mass: 200.59 amu)

• Polonium (#84 209 amu)

Multiple Choice

Element Z has 2 natural isotopes. One isotope has a mass of 15.0 amu and a relative abundance of 30%. The other isotope has a mass of 16.0 amu and a relative abundance of 70%. Estimate the average atomic mass for this one element.

• 15.0 amu

• 16.0 amu

• 15.7 amu

• 16.9 amu

Multiple Choice

Chromium has four naturally occurring isotopes (chromium-50, chromium-52, chromium-53, and chromium-54). Which isotope would you predict is the most abundant? (Hint: You will need to look at the average atomic mass of chromium on the periodic table to make your decision.)

• chromium-50

• chromium-52

• chromium-53

• chromium-54

Multiple Choice

Which has more protons?

• neither

• carbon - 12

• carbon - 13

Multiple Choice

Which has more electrons?

• neither

• carbon - 12

• carbon - 13

Multiple Choice

Which has more neutrons?

• neither

• carbon - 12

• carbon - 13

Fill in the Blank

What is the most abundant isotope? (answer in hyphen notation)

Fill in the Blank

What is the most abundant isotope? (answer in hyphen notation)

Ions

• Ion means charged atom

• To be charged it needs more or less electrons than protons

• more electrons = NEGATIVE

• less electrons = POSITIVE

Ion Notation

• Same as isotope

• includes charge in upper right

• + means LESS ELECTRONS than PROTONS

• (-) means MORE ELECTRONS than PROTONS

Multiple Choice

How many protons?

• 36

• 17

• 18

• 19

Multiple Choice

How many neutrons?

• 36

• 17

• 18

• 19

Multiple Choice

How many electrons?

• 36

• 17

• 18

• 19

Multiple Choice

How many protons?

• 9

• 4

• 5

• 2

Multiple Choice

How many neutrons?

• 9

• 4

• 5

• 2

Multiple Choice

How many electrons?

• 9

• 4

• 5

• 2

Multiple Choice

If a proton is added or removed from an atom, what happens?

• It becomes a different element.

• It becomes a different isotope.

• Nothing happens.

Multiple Choice

How many neutrons are in 1 atom of Carbon-13?

• 6

• 13

• 7

• 20

Multiple Choice

Which is the correct symbol for Fluorine-18?

Multiple Choice

What do these isotopes of carbon all have in common?

• neutrons & mass number
• atomic number and neutrons
• atomic number and electrons
• protons, atomic number, and mass number

Multiple Choice

which atom has  4 neutrons?

• Li-6
• Li-7
• Li-8
• they have the same # of neutrons

Multiple Choice

Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208.  The average atomic mass of lead is 207.2.  Which isotope of lead is likely to be the most abundant.

• 204
• 206
• 207
• 208

Multiple Choice

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
What is the average mass of this element?

• 74.92 amu
• 24.97 amu
• 75.01 amu
• 74.51 amu

Multiple Choice

What does the 1.00794 stand for?

• Hydrogen
• atomic number
• atomic mass
• atomic explosion

Multiple Choice

The atomic mass of an element is the ___.

• average of the mass number and the atomic number for the element

• weighted average of the masses of the isotopes of the element

• total mass of the isotopes of the element

• total number of subatomic particles in the nucleus

Multiple Choice

Oxygen has 8 protons. What is oxygen's atomic number?

• 16
• 8
• 15.999
• 0

Multiple Choice

A neutral atom of Carbon-13 has ________ electrons and _________ neutrons

• 13, 13
• 6, 7
• 7, 7
• 6, 6

Multiple Choice

The average atomic mass on the periodic table is found from...

• calculating the weighted average mass of all the isotopes of that element

• Calculating different types of elements together

• calculations the average of all elements in that period together.

• making a guess about how much all the isotopes might wiegh together.

Multiple Choice

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu
• 42.19 amu
• 10.43 amu
• 40.04 amu

Multiple Choice

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

Multiple Choice

What is the name of the atom pictured here?

• Nitrogen
• Nitrogen-15
• Nitrogen-7
• Nitrogen-8

Multiple Choice

The vertical (up and down) columns in the Periodic Table are called

• groups

• towers

• periods

• atomic numbers

Multiple Choice

Write the hyphen notation for the isotope that has 39 protons and 50 neutrons.

• Yttrium-11

• Tin-39

• Tin-89

• Yttrium-89

Multiple Choice

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu
• 42.19 amu
• 10.43 amu
• 40.04 amu

Multiple Choice

A Bromine ion gains 1 electron, which of the following is the correct symbol for a Bromine ion?

• Br^-1

• Br⁺¹

• Br⁺⁷

• Br^-7

Multiple Choice

An atom becomes _______ when it loses electrons.

• Positive
• Negative
• Neutral
• Invinsible

Multiple Choice

What is the charge of an atom that has lost one electron?

• -1
• -2
• +1
• +2