Question 1

Which of the following best describes an element?

Accepted Answer

A substance that cannot be broken down into other substances by chemical reactions.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Carbon, hydrogen, oxygen, and nitrogen

Question 3

What is the atomic number of an element?

Accepted Answer

The number of protons in its nucleus

Question 4

Radioactive isotopes are useful in medicine because:

Accepted Answer

They decay spontaneously, releasing particles and energy that can be tracked.

Question 5

Which statement about potential energy in electrons is correct?

Accepted Answer

Electrons in shells farther from the nucleus have higher potential energy.

Question 6

An atom with a full valence shell is:

Accepted Answer

Chemically inert

Question 7

Which of the following best explains why sodium and chlorine form an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract.

Question 8

Which equation correctly represents the photosynthesis reaction?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 9

Which type of bond involves the sharing of a pair of valence electrons between two atoms?

Accepted Answer

Covalent bond

Question 10

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

Accepted Answer

Polar covalent bonds have unequal sharing of electrons due to differences in electronegativity.

Question 11

Which of the following is a trace element required by humans in minute quantities?

Accepted Answer

Iron

Question 12

A molecule’s shape is determined primarily by:

Accepted Answer

The arrangement of its atoms’ orbitals

Question 13

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Question 14

Which scenario best illustrates the importance of molecular shape in biology?

Accepted Answer

The ability of morphine to bind to endorphin receptors due to similar shapes.

Question 15

Which of the following is true about van der Waals interactions?

Accepted Answer

They are weak attractions that occur when molecules are close together due to temporary charges.

Question 16

If an atom has 8 protons, 8 neutrons, and 8 electrons, what is its atomic mass?

Accepted Answer

$$16$$

Question 17

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions make and break chemical bonds.

Question 18

What is the main reason that weak chemical bonds are important in biological systems?

Accepted Answer

They enable large biological molecules to be held in functional forms and allow reversibility.

Question 19

Which of the following best describes an ion?

Accepted Answer

An atom or molecule with a net electrical charge due to loss or gain of electrons.

Question 20

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

The Chemical Context of Life: Foundations for General Biology

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