Question 1

Which four elements make up approximately 96% of the mass of living organisms?

Accepted Answer

Hydrogen, Oxygen, Nitrogen, Carbon

Question 2

An atom of carbon-14 has 6 protons, 8 neutrons, and 6 electrons. Which of the following statements is correct about this isotope?

Accepted Answer

It is radioactive and will decay over time.

Question 3

Which of the following best explains why atoms are considered mostly empty space?

Accepted Answer

The nucleus is very small compared to the overall size of the atom, and electrons occupy a large volume around it.

Question 4

Which property of an atom determines its chemical identity?

Accepted Answer

The number of protons in its nucleus

Question 5

A molecule of water (H$$_2O) is $$held together by which type of bond between the hydrogen and oxygen atoms?

Accepted Answer

Polar covalent bond

Question 6

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom

Question 7

Which of the following is an example of a van der Waals interaction?

Accepted Answer

Temporary attractions between nonpolar molecules due to momentary uneven electron distribution

Question 8

If an atom has an atomic number of 8 and a mass number of 16, how many neutrons does it have?

Accepted Answer

$$16 - 8 = 8$$ neutrons

Question 9

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 10

Which type of bond is responsible for the formation of table salt (NaCl)?

Accepted Answer

Ionic bond

Question 11

Why is carbon uniquely suited to form a wide variety of organic molecules?

Accepted Answer

It can form four covalent bonds with other atoms, allowing for complex structures.

Question 12

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 13

A patient is exposed to a radioactive isotope used in medical imaging. What property of this isotope makes it useful for imaging?

Accepted Answer

It emits radiation as its nucleus decays, which can be detected by imaging equipment.

Question 14

Which of the following best describes the relationship between atomic number and element identity?

Accepted Answer

The atomic number is equal to the number of protons, which defines the element.

Question 15

Which of the following is a real-world example of a hydrogen bond?

Accepted Answer

The attraction between water molecules that allows insects to walk on water

Question 16

Which of the following best explains why oxygen is essential for life on Earth?

Accepted Answer

It is highly electronegative and plays a key role in cellular respiration.

Question 17

A scientist discovers a new element with 12 protons, 12 neutrons, and 12 electrons. What is the atomic mass of this element?

Accepted Answer

$$12 + 12 = 24$$

Question 18

Which of the following statements about covalent bonds is correct?

Accepted Answer

Covalent bonds involve the sharing of electron pairs between atoms.

Question 19

Which of the following best describes the role of electrons in determining the chemical behavior of an atom?

Accepted Answer

Electrons in the outermost shell (valence electrons) determine how an atom interacts with other atoms.

Question 20

Which of the following is a correct statement about the mass of protons and neutrons?

Accepted Answer

The mass of protons and neutrons is nearly equal and is approximately $$1.7 	imes 10$$^{-24}$$ grams.

Atoms, Bonds, Carbon, and Water: The Chemical Basis of Life

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