Question 1

Which statement best describes an element as defined in biology?

Accepted Answer

An element is a collection of atoms of the same type that cannot be broken down into other substances by chemical reactions.

Question 2

What is the atomic number of an element?

Accepted Answer

The number of protons in the nucleus of an atom.

Question 3

Which subatomic particle is responsible for the chemical behavior of an atom?

Accepted Answer

Electrons in the outermost shell

Question 4

A sodium atom has 11 protons, 12 neutrons, and 11 electrons. What is its atomic mass?

Accepted Answer

$$23$$

Question 5

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed when two atoms share electrons.

Question 6

What is the main difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve the sharing of electrons unequally, resulting in partial charges on the molecule.

Question 7

Which of the following is true about hydrogen bonds?

Accepted Answer

Hydrogen bonds are about 20 times easier to break than covalent bonds.

Question 8

Why do water molecules tend to stick together?

Accepted Answer

Because of hydrogen bonds formed between polar water molecules.

Question 9

Which of the following best explains why sodium chloride (NaCl) forms crystals?

Accepted Answer

NaCl forms crystals due to ionic bonds between oppositely charged sodium and chloride ions.

Question 10

If an atom has an almost empty or almost full outer electron shell, what is it most likely to do?

Accepted Answer

Form an ion by gaining or losing electrons.

Question 11

Which statement about electron shells is correct?

Accepted Answer

Each electron shell occupies a specific distance from the nucleus; the further away, the higher the energy level.

Question 12

Which of the following is a correct definition of a molecule?

Accepted Answer

A molecule is two or more atoms held together by chemical bonds.

Question 13

Which type of bond is responsible for the three-dimensional shape of large biological molecules?

Accepted Answer

Hydrogen bonds

Question 14

A molecule of nitrogen gas ($$N_2) $$contains three pairs of shared electrons between the two nitrogen atoms. What type of bond is this?

Accepted Answer

Triple covalent bond

Question 15

Which of the following best describes a mixture?

Accepted Answer

A mixture is composed of two or more elements or compounds in a variable ratio.

Question 16

Which of the following statements about water is correct?

Accepted Answer

Water covers about 70% of the surface of the earth.

Question 17

Which of the following is true about the charge distribution in a water molecule?

Accepted Answer

The oxygen atom has a partial negative charge and the hydrogen atoms have a partial positive charge.

Question 18

Which of the following is a consequence of the polarity of water molecules?

Accepted Answer

Water molecules form hydrogen bonds with each other.

Question 19

Which of the following is NOT a property of ionic compounds?

Accepted Answer

They are held together by the sharing of electrons.

Question 20

Which statement best explains why oxygen in a water molecule has a partial negative charge?

Accepted Answer

Oxygen has more protons than hydrogen, attracting electrons more strongly.

Atoms, Molecules, and Life: Foundations of Biological Chemistry

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