Question 1

Which of the following statements best explains why oxygen atoms can form two covalent bonds?

Accepted Answer

Oxygen has six electrons in its valence shell and needs two more to complete it, allowing it to form two covalent bonds.

Question 2

Which of the following best describes the difference between an element and a compound?

Accepted Answer

An element is a substance that cannot be broken down by chemical reactions, while a compound consists of two or more elements combined in fixed ratios.

Question 3

Given the atomic number ($$Z) $$and mass number ($$A) of an $$atom, which formula correctly calculates the number of neutrons ($$N) in $$the atom?

Accepted Answer

$$N = A - Z$$

Question 4

A radioactive isotope of carbon has an atomic number of 6 and a mass number of 14. How many neutrons does it have?

Accepted Answer

8

Question 5

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.

Question 6

Which element makes up the largest percentage of body mass in humans, including water?

Accepted Answer

Oxygen

Question 7

What is the main reason noble gases are chemically inert?

Accepted Answer

They have a full valence electron shell.

Question 8

Which of the following molecules contains a polar covalent bond?

Accepted Answer

H$$_2O$$

Question 9

If sodium (Na) transfers an electron to chlorine (Cl), what type of ions are formed?

Accepted Answer

Na becomes a cation and Cl becomes an anion.

Question 10

Which of the following best explains why water molecules can form hydrogen bonds?

Accepted Answer

The oxygen atom in water is highly electronegative, creating partial charges that allow hydrogen bonds to form.

Question 11

A molecule of formic acid (CH$$_2O$_2) $$contains which types of atoms?

Accepted Answer

Carbon, hydrogen, and oxygen

Question 12

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which formula represents the calculation of atomic mass ($$M) of an $$atom, given the number of protons ($$p) $$and neutrons ($$n$$)?

Accepted Answer

$$M = p + n$$

Question 14

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of one or more pairs of valence electrons between atoms.

Question 15

Which of the following is a real-world example of an ionic compound?

Accepted Answer

Sodium chloride (NaCl)

Question 16

Which property of atoms primarily determines their chemical behavior?

Accepted Answer

The distribution of electrons in the electron shells, especially the valence electrons

Question 17

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity is the attraction of an atom for the electrons in a covalent bond.

Question 18

Which of the following best describes a nonpolar covalent bond?

Accepted Answer

A bond in which electrons are shared equally between atoms.

Question 19

Which of the following is a consequence of unequal sharing of electrons in a polar covalent bond?

Accepted Answer

Each atom acquires a partial positive or negative charge.

Question 20

Which of the following best explains why sodium chloride forms a crystal lattice structure?

Accepted Answer

The oppositely charged ions are attracted to each other and arrange themselves in a repeating pattern.

Chapter 2: The Chemical Context of Life – Study Notes

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