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

Oxygen, carbon, hydrogen, and nitrogen make up approximately what percentage of living matter?

Accepted Answer

About 96%

Question 3

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 4

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. What property makes it useful for this purpose?

Accepted Answer

It emits energy as it decays, which can be detected by imaging equipment.

Question 5

Which subatomic particle is directly involved in chemical reactions between atoms?

Accepted Answer

Electron

Question 6

Which of the following best explains why glucose has more potential energy than water?

Accepted Answer

Glucose has more chemical bonds, which store potential energy.

Question 7

What determines the chemical behavior of an atom?

Accepted Answer

The distribution of electrons in the atom's electron shells.

Question 8

How many valence electrons does a carbon atom have?

Accepted Answer

$$4$$

Question 9

Which of the following best describes a covalent bond?

Accepted Answer

The sharing of a pair of valence electrons by two atoms.

Question 10

What is the valence of nitrogen?

Accepted Answer

$$3$$

Question 11

Which of the following molecules is NOT a compound?

Accepted Answer

Oxygen ($$O_2)$$

Question 12

What type of bond is formed when two oxygen atoms share two pairs of valence electrons?

Accepted Answer

Double covalent bond

Question 13

Which of the following best describes electronegativity?

Accepted Answer

The ability of an atom to attract electrons toward itself in a covalent bond.

Question 14

Which statement best explains the difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

In a polar covalent bond, electrons are shared unequally between atoms; in a nonpolar covalent bond, electrons are shared equally.

Question 15

What happens during the formation of an ionic bond between sodium and chlorine?

Accepted Answer

Sodium donates an electron to chlorine, forming oppositely charged ions that attract each other.

Question 16

In the formation of sodium chloride ($$NaCl$$), which ion is the cation?

Accepted Answer

Sodium ion ($$Na^+)$$

Question 17

What is a hydrogen bond?

Accepted Answer

A weak attraction between a partially positive hydrogen atom and a partially negative atom of another molecule.

Question 18

Which of the following best describes van der Waals interactions?

Accepted Answer

Weak attractions between molecules due to temporary local partial charges.

Question 19

A solution has a pH of $$5. $$How many times more acidic is it than a solution with a pH of $$7$$?

Accepted Answer

$$100$$ times

Question 20

Which of the following is a trace element required by vertebrates but not all forms of life?

Accepted Answer

Iodine

Chemical Elements and Bonding in Biological Systems: Study Notes

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