$$\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following statements best explains why table salt (NaCl) forms a crystal lattice structure when solid?

Accepted Answer

The sodium and chloride ions are attracted to each other by ionic bonds, arranging themselves in a repeating pattern.

Question 2

A radioactive isotope of carbon, carbon-14, is used in radiometric dating. Which of the following statements about carbon-14 is correct?

Accepted Answer

Carbon-14 has 6 protons and 8 neutrons, giving it a mass number of 14.

Question 3

Which element is the most abundant in the human body by mass, and what is its approximate percentage?

Accepted Answer

Oxygen, 65.0\%

Question 4

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule is any group of atoms bonded together, while a compound is a molecule that contains at least two different elements in a fixed ratio.

Question 5

Which of the following equations correctly represents the calculation of the mass number of an atom?

Accepted Answer

$$	ext{Mass number} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 6

Why is water (H$$_2O) $$considered a polar molecule?

Accepted Answer

The oxygen atom is more electronegative than the hydrogen atoms, causing an unequal sharing of electrons.

Question 7

Which of the following best explains why noble gases such as helium (He) are chemically inert?

Accepted Answer

They have a full valence shell of electrons.

Question 8

A hydrogen bond is most likely to form between which of the following pairs of atoms?

Accepted Answer

A hydrogen atom covalently bonded to oxygen and another oxygen atom in a different molecule.

Question 9

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 10

Which of the following best describes the process that occurs when sodium (Na) reacts with chlorine (Cl) to form sodium chloride (NaCl)?

Accepted Answer

Sodium donates an electron to chlorine, forming Na$$^+$$ and Cl$$^-$$ ions that are held together by ionic bonds.

Question 11

Which of the following is the correct electron configuration for a neutral carbon atom (atomic number 6)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^2$$

Question 12

Which of the following best explains why formic acid (CH$$_2O$_2) $$has different properties than its constituent elements?

Accepted Answer

A compound has characteristics different from those of its elements due to the specific arrangement and bonding of atoms.

Question 13

Which of the following elements is NOT one of the four most abundant elements in the human body?

Accepted Answer

Phosphorus (P)

Question 14

If an atom has an atomic number of 7 and a mass number of 15, how many neutrons does it have?

Accepted Answer

$$15 - 7 = 8$$ neutrons

Question 15

Which of the following best describes a nonpolar covalent bond?

Accepted Answer

Electrons are shared equally between two atoms.

Question 16

Which of the following is a real-world example of the importance of trace elements in biology?

Accepted Answer

A deficiency in iodine can lead to thyroid gland problems in humans.

Question 17

Which of the following best explains why atoms form chemical bonds?

Accepted Answer

To achieve a full valence shell of electrons and become more stable.

Question 18

Which of the following is true about the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is equal to the number of protons and determines the element's identity.

Question 19

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are involved in forming chemical bonds because they are in the outermost shell.

The Chemical Context of Life: Atoms, Elements, and Chemical Bonds

Study Guide - Practice Questions