Question 1

Which of the following best explains why sodium (Na), a reactive metal, and chlorine (Cl), a poisonous gas, combine to form table salt (NaCl), which is safe to eat?

Accepted Answer

The combination of sodium and chlorine results in a compound with emergent properties different from those of the individual elements.

Question 2

Which four elements make up approximately 96% of the human body’s mass?

Accepted Answer

Oxygen, carbon, hydrogen, and nitrogen

Question 3

A neutral atom of sodium has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$

Question 4

Which statement best describes the difference between a covalent bond and an ionic bond?

Accepted Answer

A covalent bond involves the sharing of electrons, while an ionic bond involves the transfer of electrons.

Question 5

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

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

Question 6

Which type of bond is primarily responsible for holding together the two strands of DNA?

Accepted Answer

Hydrogen bonds

Question 7

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

Accepted Answer

Atomic number = 8, Mass number = 16

Question 8

Which of the following best describes a hydrogen bond?

Accepted Answer

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

Question 9

Which of the following is a trace element required by vertebrates for normal thyroid function?

Accepted Answer

Iodine (I)

Question 10

What is the maximum number of electrons that can occupy a single orbital?

Accepted Answer

2

Question 11

Which of the following best describes the energy change when an electron moves from a lower to a higher electron shell?

Accepted Answer

The electron absorbs energy equal to the difference between the two shells.

Question 12

Which of the following is an example of an emergent property?

Accepted Answer

Table salt (NaCl) is edible, while its component elements are not.

Question 13

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

Accepted Answer

They have full valence shells.

Question 14

Which of the following best describes van der Waals interactions?

Accepted Answer

Weak attractions due to temporary partial charges from uneven electron distribution.

Question 15

Which of the following is true about the molecular shape of methane (CH$$_4$$)?

Accepted Answer

It forms a tetrahedral shape due to the hybridization of orbitals.

Question 16

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

Accepted Answer

They are the electrons in the outermost shell and determine an atom’s chemical behavior.

Question 17

Which of the following is a real-life example of van der Waals interactions?

Accepted Answer

A gecko climbing a wall using thousands of tiny hairs on its toes.

Question 18

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 19

Which of the following is the best analogy for chemical equilibrium in a reaction?

Accepted Answer

When equal numbers of squirrels are entering and leaving a room.

Question 20

Which of the following best explains why the shape of a molecule is important in biology?

Accepted Answer

Molecular shape determines how biological molecules recognize and respond to each other.

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

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