Q: Which of the following is the correct formula for calculating the atomic mass of an atom?

Atomic mass $$= \text{number of protons} + \text{number of neutrons}$$

Question 1

Which of the following statements best describes an element?

Accepted Answer

An element is a substance that cannot be broken down into other substances by chemical means and is defined by its number of protons.

Question 2

Which of the following is the correct formula for calculating the atomic mass of an atom?

Accepted Answer

Atomic mass $$= 	ext{number of protons} + 	ext{number of neutrons}$$

Question 3

Carbon-12 and Carbon-14 are examples of:

Accepted Answer

Isotopes

Question 4

Which of the following best explains why water is considered an excellent solvent?

Accepted Answer

Water molecules are polar, allowing them to surround and separate charged and polar substances.

Question 5

If an oxygen atom gains two electrons, what is its resulting charge?

Accepted Answer

$$-2$$

Question 6

Which of the following ions is most important for nerve impulse transmission in humans?

Accepted Answer

$$\mathrm{Na^+}$$

Question 7

What is the main difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from one atom to another, while covalent bonds involve the sharing of electrons between atoms.

Question 8

Which property of water allows insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 9

A radioactive isotope can be used as a biological tracer because:

Accepted Answer

It can be detected due to its radioactive emissions, allowing scientists to track its movement in biological systems.

Question 10

Which of the following best describes the octet rule?

Accepted Answer

Atoms are most stable when their outermost electron shell contains 8 electrons.

Question 11

Which of the following is NOT one of the four elements that make up the bulk of living cells?

Accepted Answer

Calcium

Question 12

If a sodium atom ($$\mathrm{Na}) $$loses one electron, what is its resulting charge?

Accepted Answer

$$+1$$

Question 13

Which of the following best explains why isotopes of the same element have different physical properties?

Accepted Answer

They have different numbers of neutrons, which affects their mass and stability.

Question 14

Which of the following is a correct statement about ions?

Accepted Answer

An ion is an atom that has gained or lost electrons, resulting in a net electrical charge.

Question 15

Which of the following best describes the role of electrons in chemical bonding?

Accepted Answer

Electrons in the outermost shell (valence electrons) are involved in forming chemical bonds.

Question 16

Which of the following is a real-world application of radioactive isotopes in medicine?

Accepted Answer

Using radioactive isotopes as biological tracers to detect tumors in PET scans.

Question 17

Which of the following equations correctly represents the relationship between the number of protons ($$p$$), neutrons ($$n$$), and electrons ($$e) in a $$neutral atom?

Accepted Answer

$$p = e$$

Question 18

Which property of water helps moderate Earth's climate by absorbing heat without a large increase in temperature?

Accepted Answer

Water's high specific heat

Question 19

A molecule of water ($$\mathrm{H_2O}) is $$held together by which type of bond?

Accepted Answer

Covalent bond

Question 20

Which of the following best explains why sodium chloride ($$\mathrm{NaCl}) $$forms an ionic bond?

Accepted Answer

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

The Chemical Foundations of Life: Atoms, Elements, and Water in Biology

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