Question 1

Which of the following statements best describes a key insight from J.J. Thomson's cathode ray experiment?

Accepted Answer

The nature of the rays Thomson studied was that they consisted of a fundamental unit of charge, later identified as the electron.

Question 2

A neutral sodium atom ($$Z=11) $$loses one electron. What is the resulting ion and its charge?

Accepted Answer

It becomes a cation with a $$+1$$ charge: $$\mathrm{Na}^+.$$

Question 3

Which of the following best describes a metalloid?

Accepted Answer

A substance that conducts heat and electricity moderately well and possesses some properties of both metals and nonmetals.

Question 4

Which of the following is the correct empirical formula for acetic acid ($$\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$$)?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 5

A chlorine sample contains two isotopes: $$^{35}\mathrm{Cl} ($$mass = $$34.969$$ amu, abundance = $$75.77\%) $$and $$^{37}\mathrm{Cl} ($$mass = $$36.966$$ amu, abundance = $$24.23\%). $$What is the average atomic mass of chlorine? (Round to two decimal places.)

Accepted Answer

$$35.45$$ amu

Question 6

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 7

Which of the following is the correct molecular formula for benzene if its empirical formula is $$\mathrm{CH}$$?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_6$$

Question 8

A neutral oxygen atom ($$Z=8) $$gains two electrons. What is the resulting ion and its charge?

Accepted Answer

It becomes an anion with a $$-2$$ charge: $$\mathrm{O}^{2-}.$$

Question 9

Which of the following best describes the relationship between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons; mass number is the sum of protons and neutrons.

Question 10

Which of the following is a correct example of an ionic compound and its ions?

Accepted Answer

$$\mathrm{NaCl}$$: $$\mathrm{Na}^+ ($$cation), $$\mathrm{Cl}^- ($$anion)

Question 11

If an atom has 20 protons, 22 neutrons, and 18 electrons, what is its symbol with charge?

Accepted Answer

$$^{42}\mathrm{Ca}^{2+}$$

Question 12

Which scientist is credited with discovering the periodic table's organizational principle?

Accepted Answer

Dmitry Mendeleev

Question 13

A sample of boron contains $$19.9\%$$ $$^{10}\mathrm{B} ($$mass = $$10.0129$$ amu) and $$80.1\%$$ $$^{11}\mathrm{B} ($$mass = $$11.0093$$ amu). What is the average atomic mass of boron? (Round to two decimal places.)

Accepted Answer

$$10.81$$ amu

Question 14

Which of the following best describes a nonmetal?

Accepted Answer

Appears dull and is a poor conductor of heat and electricity.

Question 15

Which of the following is the correct way to write the atomic symbol for an isotope of magnesium with 12 protons and 13 neutrons?

Accepted Answer

$$^{25}\mathrm{Mg}$$

Question 16

Which of the following best explains why the periodic table is useful to chemists?

Accepted Answer

It shows the relationship among properties of elements and organizes them in rows (periods) and columns (groups).

Question 17

A neutral atom of chromium ($$Z=24) $$has a mass number of $$52. $$How many protons, neutrons, and electrons does it have?

Accepted Answer

24 protons, 28 neutrons, 24 electrons

Question 18

Which of the following best describes the difference between a molecular formula and an empirical formula?

Accepted Answer

A molecular formula shows the actual number of atoms of each element in a molecule, while an empirical formula shows the simplest whole-number ratio.

Question 19

Which of the following ions is formed when a neutral atom of aluminum ($$Z=13) $$loses three electrons?

Accepted Answer

$$\mathrm{Al}^{3+}$$

Fundamental Concepts in General Chemistry: Atomic Theory, Atomic Structure, and the Periodic Table

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