Question 1

Which experiment led to the discovery that most of an atom's mass and all of its positive charge are concentrated in a small nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

A neutral atom of magnesium has an atomic number of 12. If it forms a $$\mathrm{Mg$$^{2+}$$}$$ ion, how many electrons does it have?

Accepted Answer

10 electrons

Question 3

Which of the following statements best explains why most alpha particles passed through the gold foil in Rutherford’s experiment?

Accepted Answer

Atoms are mostly empty space

Question 4

A chlorine isotope has 17 protons and 18 neutrons. What is its isotope symbol in the $$\mathrm{Z^A\,Element}$$ format?

Accepted Answer

$$\mathrm{^{35}_{17}Cl}$$

Question 5

Which element is a main-group metal, is found in Group 1A, and forms a $$1+$$ ion?

Accepted Answer

Potassium (K)

Question 6

A neutral atom has 6 protons, 6 neutrons, and 6 electrons. What is its mass in amu and its charge?

Accepted Answer

12 amu, charge-neutral

Question 7

Which of the following is NOT a property of metals?

Accepted Answer

Tend to gain electrons

Question 8

Calculate the atomic mass of gallium given the following data: Ga-69 (mass $$=68.9256$$ amu, abundance $$=60.11\%$$), Ga-71 (mass $$=70.9247$$ amu, abundance $$=39.89\%). $$Use the formula $$	ext{Atomic mass} = \sum (	ext{isotopic mass} 	imes 	ext{fractional abundance}).$$

Accepted Answer

$$69.72$$ amu

Question 9

Which element has a chemical symbol based on its Latin name?

Accepted Answer

Sodium (Na)

Question 10

A sulfur ion ($$\mathrm{S$$^{2-}$$}) $$has how many protons and electrons?

Accepted Answer

16 protons, 18 electrons

Question 11

Which group of elements is known as the noble gases and is characterized by being inert?

Accepted Answer

Group 8A

Question 12

If an atom has a mass number of 27 and 14 neutrons, what is its atomic number and which element is it?

Accepted Answer

Atomic number $$=13$$, Aluminum (Al)

Question 13

Which of the following ions has the same number of electrons as $$\mathrm{Na^+}$$?

Accepted Answer

$$\mathrm{Mg$$^{2+}$$}$$

Question 14

Which of the following statements about isotopes is TRUE?

Accepted Answer

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

Question 15

Which element is both a metalloid and a halogen?

Accepted Answer

Astatine (At)

Question 16

A neutral atom of iron has 26 electrons. If it forms a $$\mathrm{Fe$$^{3+}$$}$$ ion, how many electrons does it have?

Accepted Answer

23 electrons

Question 17

Which of the following best describes the trend for main-group elements forming ions?

Accepted Answer

Alkali metals lose 1 electron to form $$1+$$ ions; halogens gain 1 electron to form $$1-$$ ions

Question 18

Which of the following is a transition element?

Accepted Answer

Iron (Fe)

Question 19

A sample of chlorine contains $$75.77\%$$ $$\mathrm{Cl-35} ($$mass $$=34.97$$ amu) and $$24.23\%$$ $$\mathrm{Cl-37} ($$mass $$=36.97$$ amu). What is the atomic mass of chlorine? Use $$	ext{Atomic mass} = (0.7577 	imes 34.97) + (0.2423 	imes 36.97).$$

Accepted Answer

$$35.45$$ amu

Question 20

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

Accepted Answer

It is a weighted average of the masses of all naturally occurring isotopes

Atoms, Elements, and the Structure of Matter: Study Notes for Introduction to Chemistry

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