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

Question 1

Which subatomic particle is primarily responsible for determining the chemical properties and reactivity of an element?

Accepted Answer

Electron

Question 2

A neutral atom of phosphorus has an atomic number of 15 and a mass number of 31. How many neutrons does it contain?

Accepted Answer

16

Question 3

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the transfer of electrons from one atom to another

Question 4

What is the charge of a magnesium ion ($$\mathrm{Mg$$^{2+}$$}) $$after it loses two electrons?

Accepted Answer

$$+2$$

Question 5

Which element is the most electronegative according to the Pauling scale provided in the study materials?

Accepted Answer

Oxygen

Question 6

A molecule of water ($$\mathrm{H_2O}) $$exhibits which type of covalent bond between its atoms?

Accepted Answer

Polar covalent bond

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have different numbers of neutrons

Question 8

During a chemical reaction, which of the following occurs?

Accepted Answer

Chemical bonds are broken and new bonds are formed

Question 9

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

Their valence shells are completely filled with electrons

Question 10

If a sulfur atom gains two electrons, what is the symbol and charge of the resulting ion?

Accepted Answer

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

Question 11

Which type of chemical bond is responsible for the unique properties of water, such as its high boiling point and surface tension?

Accepted Answer

Hydrogen bonds

Question 12

Which of the following is a real-world example of a compound formed by ionic bonding?

Accepted Answer

Sodium chloride ($$\mathrm{NaCl})$$

Question 13

Which formula correctly calculates the mass number of an atom?

Accepted Answer

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

Question 14

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons and has a positive charge

Question 15

Which of the following molecules contains only nonpolar covalent bonds?

Accepted Answer

Methane ($$\mathrm{CH_4$})$$

Question 16

Which of the following is true about chemical reactions in biological systems, such as photosynthesis?

Accepted Answer

The number of atoms in the reactants is always equal to the number of atoms in the products

Question 17

Which of the following best explains the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing

Question 18

Which of the following weak interactions is most important for the three-dimensional structure of proteins?

Accepted Answer

Hydrogen bonds

Question 19

If an atom has 8 protons, 8 neutrons, and 10 electrons, what is its net charge?

Accepted Answer

$$-2$$

Question 20

Which of the following is NOT considered matter?

Accepted Answer

Light

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

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