Q: Which of the following equations correctly represents the calculation of atomic mass?

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

Question 1

Which of the following statements best explains why sodium chloride (NaCl) has properties different from those of its constituent elements, sodium and chlorine?

Accepted Answer

NaCl is a compound, and compounds have characteristics different from the elements that form them.

Question 2

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 3

A carbon atom has 6 protons, 6 neutrons, and 6 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number = 6, Mass number = 12

Question 4

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 5

What is the main reason that elements with a full valence shell are chemically inert?

Accepted Answer

Their outermost electron shell is full, so they do not tend to gain, lose, or share electrons.

Question 6

Which of the following equations correctly represents the calculation of atomic mass?

Accepted Answer

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

Question 7

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of a pair of valence electrons between two atoms

Question 8

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

Accepted Answer

In a polar covalent bond, electrons are shared unequally; in a nonpolar covalent bond, electrons are shared equally.

Question 9

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.

Question 10

Which of the following is true about ionic bonds?

Accepted Answer

They are formed by the attraction between oppositely charged ions.

Question 11

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

Accepted Answer

Na$$^+$$ has a positive charge because it has more protons than electrons.

Question 12

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 13

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

Accepted Answer

Oxygen

Question 14

If an atom has 7 protons, 7 neutrons, and 7 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number = 7, Mass number = 14

Question 15

Which of the following best explains why radioactive isotopes are useful in medical imaging?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be detected.

Question 16

Which of the following equations correctly represents the relationship between atomic number ($$Z$$), number of protons ($$p$$), and number of neutrons ($$n$$)?

Accepted Answer

$$Z = p$$

Question 17

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

Accepted Answer

Sodium chloride (NaCl), which is table salt and essential for nerve function in humans.

Question 18

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

Accepted Answer

Valence electrons are involved in forming bonds with other atoms.

Question 19

Which of the following statements about the periodic table is correct?

Accepted Answer

It shows the electron distribution for each element, which helps predict chemical behavior.

Question 20

A molecule of formic acid (CH$$_2O$_2) $$contains which of the following elements?

Accepted Answer

Carbon, hydrogen, and oxygen

Chapter 2: The Chemical Context of Life – Study Notes

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