$$\text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following statements best explains why water is considered essential in the search for extraterrestrial life?

Accepted Answer

Water is a universal solvent, allowing many biochemical reactions necessary for life to occur.

Question 2

Which of the following best describes the Bohr model of the atom?

Accepted Answer

Electrons occupy orbits or shells around a central nucleus, which contains protons and neutrons.

Question 3

A neutral atom of carbon has an atomic number of 6. How many electrons and protons does it have?

Accepted Answer

6 electrons and 6 protons

Question 4

Which of the following elements is most likely to form four covalent bonds in biological molecules?

Accepted Answer

Carbon

Question 5

The mass number of an atom is calculated as:

Accepted Answer

$$	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 6

Which property of water is primarily responsible for its ability to moderate Earth's climate by absorbing heat energy?

Accepted Answer

High heat capacity

Question 7

If two atoms have very different electronegativities, what type of bond are they most likely to form?

Accepted Answer

Ionic bond

Question 8

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between the $$\delta^-$$ end of one molecule and the $$\delta^+$$ hydrogen end of another molecule.

Question 9

Why does water have a high heat of vaporization?

Accepted Answer

Because hydrogen bonds between water molecules require a lot of energy to break.

Question 10

Which of the following statements about covalent bonds is correct?

Accepted Answer

Covalent bonds involve the sharing of electron pairs between atoms.

Question 11

A molecule of methane ($$\mathrm{CH_4$}) $$always forms a tetrahedral shape. This is due to:

Accepted Answer

The orientation and angle of covalent bonds between carbon and hydrogen atoms.

Question 12

Which of the following best explains why water is an excellent solvent for ionic and polar substances?

Accepted Answer

Water molecules are polar, allowing them to surround and interact with charged and polar molecules.

Question 13

Which of the following is a consequence of water's high heat of vaporization for living organisms?

Accepted Answer

Evaporation of water from the skin removes heat and helps cool the body.

Question 14

If an atom has an atomic number of 8 and a mass number of 18, how many neutrons does it have?

Accepted Answer

$$18 - 8 = 10$$ neutrons

Question 15

Which of the following is NOT a property of hydrogen bonds in water?

Accepted Answer

They are stronger than covalent bonds.

Question 16

Which of the following best describes the octet rule as it applies to atoms in biological molecules?

Accepted Answer

Atoms will lose, gain, or share electrons to achieve a stable configuration of 8 electrons in their outermost shell.

Question 17

Which of the following elements has the highest electronegativity according to the provided table?

Accepted Answer

Chlorine

Question 18

A polar covalent bond is most likely to form between two atoms when:

Accepted Answer

The two atoms have different electronegativities, causing unequal sharing of electrons.

Question 19

Which of the following real-life scenarios best illustrates the concept of cohesion due to hydrogen bonding in water?

Accepted Answer

A water droplet maintaining its shape on a leaf surface.

Question 20

Which of the following statements about the relationship between atomic structure and chemical bonding is correct?

Accepted Answer

The number of electrons in the outermost shell determines the bonding behavior of an atom.

The Chemistry and Energy of Life: Atomic Structure, Chemical Bonds, and Water

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