Question 1

Which of the following statements best describes an isotope?

Accepted Answer

An atom with the same number of protons and electrons, but a different number of neutrons.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. What makes $$^{14}C$$ radioactive compared to $$^{12}C$$?

Accepted Answer

$$^{14}C$$ has an unstable nucleus due to extra neutrons, causing it to decay over time.

Question 3

Which of the following best explains why noble gases like neon are chemically inert?

Accepted Answer

Their valence electron shells are completely filled, making them stable.

Question 4

Given an atom with atomic number $$Z = 11$$ and mass number $$A = 23$$, how many neutrons does it have?

Accepted Answer

$$12$$

Question 5

Which type of chemical bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 6

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

Accepted Answer

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

Question 7

Which of the following best describes the process of oxidation in biological systems?

Accepted Answer

The loss of electrons from a molecule, often involving oxygen.

Question 8

A sodium atom ($$Na) $$loses one electron to become a sodium ion ($$Na^+). $$What is the charge of the resulting ion?

Accepted Answer

$$+1$$

Question 9

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

Accepted Answer

Using radioactive glucose to detect cancerous tissue in PET scans.

Question 10

Which equation correctly represents the photosynthesis reaction?

Accepted Answer

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

Question 11

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 12

If an atom has 8 protons, 8 neutrons, and 10 electrons, what is its net charge?

Accepted Answer

$$-2$$

Question 13

Which of the following elements is NOT one of the four most abundant elements in living organisms?

Accepted Answer

Calcium ($$Ca)$$

Question 14

What is the atomic number of an element, and what does it determine?

Accepted Answer

The number of protons in the nucleus, which determines the element's identity.

Question 15

Which of the following best explains why water molecules are polar?

Accepted Answer

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

Question 16

Which of the following is true about chemical reactions in biological systems?

Accepted Answer

Chemical reactions rearrange electrons among atoms but do not create or destroy atoms.

Question 17

A molecule of methane ($$CH_4) is $$formed when carbon shares electrons with four hydrogen atoms. What type of bond is present in methane?

Accepted Answer

Nonpolar covalent bonds

Question 18

Which of the following best describes the concept of chemical equilibrium?

Accepted Answer

The forward and reverse reactions occur at the same rate, and the concentrations of reactants and products remain constant.

Question 19

Which of the following is a consequence of the three-dimensional shape of biological molecules?

Accepted Answer

Molecular shape determines how biological molecules recognize and interact with each other.

Question 20

Which of the following best describes a van der Waals interaction?

Accepted Answer

A weak attraction between molecules due to temporary partial charges.

The Chemical Context of Life: Atoms, Elements, and Chemical Bonds

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