Q: Which of the following correctly describes the relationship between atomic number, mass number, and the number of neutrons in an atom?

$$\text{Number of neutrons} = \text{Mass number} - \text{Atomic number}$$

Q: Which calculation would you use to determine the atomic mass of an element from its isotopic abundances?

$$\text{Atomic mass} = \sum (\text{fractional abundance} \times \text{isotopic mass})$$

Question 1

A neutral atom of chlorine has 17 protons and 18 neutrons. What is the isotope symbol for this atom?

Accepted Answer

$$\mathrm{^{35}Cl}$$

Question 2

A magnesium ion has 12 protons and 10 electrons. What is the charge of this ion?

Accepted Answer

$$2^+$$

Question 3

Which of the following correctly describes the relationship between atomic number, mass number, and the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{Mass number} - 	ext{Atomic number}$$

Question 4

A sample of neon contains 90.48% $$\mathrm{^{20}Ne} ($$mass = 19.992 amu), 0.27% $$\mathrm{^{21}Ne} ($$mass = 20.994 amu), and 9.25% $$\mathrm{^{22}Ne} ($$mass = 21.991 amu). What is the atomic mass of neon?

Accepted Answer

$$20.18\ \mathrm{amu}$$

Question 5

Which of the following ions has 16 protons, 18 electrons, and 16 neutrons?

Accepted Answer

$$\mathrm{^{32}S$$^{2-}$$}$$

Question 6

A hospital uses a radioactive isotope with the symbol $$\mathrm{^{99m}Tc}$$ for imaging. If technetium has atomic number 43, how many neutrons are in $$\mathrm{^{99m}Tc}$$?

Accepted Answer

$$56$$

Question 7

Which statement is true about an anion?

Accepted Answer

It has more electrons than protons.

Question 8

A calcium ion has 20 protons, 20 neutrons, and 18 electrons. What is its isotope symbol and charge?

Accepted Answer

$$\mathrm{^{40}Ca$$^{2+}$$}$$

Question 9

Which calculation would you use to determine the atomic mass of an element from its isotopic abundances?

Accepted Answer

$$	ext{Atomic mass} = \sum (	ext{fractional abundance} 	imes 	ext{isotopic mass})$$

Question 10

A student analyzes a sample of boron and finds it contains 80.2% $$\mathrm{^{11}B} ($$mass = 11.009 amu) and 19.8% $$\mathrm{^{10}B} ($$mass = 10.012 amu). What is the atomic mass of boron?

Accepted Answer

$$10.81\ \mathrm{amu}$$

Question 11

Which of the following best describes the isotope $$\mathrm{^{14}C}$$?

Accepted Answer

It has 6 protons, 8 neutrons, and 6 electrons.

Question 12

A sodium ion is found to have 11 protons, 12 neutrons, and 10 electrons. What is its isotope symbol and charge?

Accepted Answer

$$\mathrm{^{23}Na$$^{+}$$}$$

Question 13

Which of the following would be the correct isotope symbol for an atom with 15 protons, 16 neutrons, and 18 electrons?

Accepted Answer

$$\mathrm{^{31}P$$^{3-}$$}$$

Question 14

A hospital technician prepares a solution containing $$\mathrm{^{131}I}$$ for thyroid imaging. If iodine has atomic number 53, how many neutrons are present in $$\mathrm{^{131}I}$$?

Accepted Answer

$$78$$

Question 15

Which of the following statements is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 16

A copper atom has atomic number 29 and mass number 65. How many neutrons does it have?

Accepted Answer

$$36$$

Question 17

Which of the following ions has the same number of electrons as a neutral argon atom?

Accepted Answer

$$\mathrm{Cl^-}$$

Question 18

A student is given an unknown element with atomic number 8 and mass number 18. If the atom is a $$2^-$$ ion, how many electrons does it have?

Accepted Answer

$$10$$

Question 19

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

It is a weighted average of the masses of its naturally occurring isotopes.

Question 20

A patient receives a dose of $$\mathrm{^{18}F}$$ for a PET scan. If fluorine has atomic number 9, what is the number of protons, neutrons, and electrons in a neutral $$\mathrm{^{18}F}$$ atom?

Accepted Answer

Atoms, Ions, and Isotopes: Structure and Calculations

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