Question 1

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

Accepted Answer

Oxygen has six valence electrons and needs two more to fill its valence shell, so it can form two covalent bonds.

Question 2

A radioactive isotope of carbon, carbon-14, differs from the most common carbon isotope, carbon-12, in which of the following ways?

Accepted Answer

Carbon-14 has more neutrons than carbon-12.

Question 3

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 4

Which element makes up the largest percentage of the human body by mass?

Accepted Answer

Oxygen

Question 5

A sodium atom (Na) transfers an electron to a chlorine atom (Cl), forming NaCl. After this transfer, what is the charge on the sodium ion?

Accepted Answer

$$+1$$

Question 6

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

Accepted Answer

They have a full valence shell of electrons.

Question 7

Which of the following is true about covalent bonds in a water molecule ($$\mathrm{H_2O}$$)?

Accepted Answer

The electrons are shared unequally, making the bonds polar covalent.

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 statements about isotopes is correct?

Accepted Answer

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

Question 10

A molecule of formic acid ($$\mathrm{CH_2O_2}) $$contains which of the following types of bonds?

Accepted Answer

Only covalent bonds

Question 11

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, so electrons are pulled closer to oxygen.

Question 12

If an atom has an atomic number of 7 and a mass number of 15, how many neutrons does it have?

Accepted Answer

$$8$$

Question 13

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

Accepted Answer

Sodium chloride ($$\mathrm{NaCl})$$

Question 14

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

Accepted Answer

A molecule is any group of atoms held together by covalent bonds, while a compound is a substance consisting of two or more elements in a fixed ratio.

Question 15

Which of the following elements is NOT one of the four most abundant elements in the human body?

Accepted Answer

Calcium

Question 16

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond?

Accepted Answer

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

Question 17

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons determine the chemical behavior of an atom.

Question 18

A patient is exposed to a radioactive isotope used in medical imaging. Which property of the isotope is most important for this application?

Accepted Answer

It decays spontaneously, emitting particles and energy that can be detected.

Question 19

Which of the following best describes electronegativity?

Accepted Answer

The ability of an atom to attract electrons in a covalent bond.

Question 20

Which of the following is the correct molecular formula for formic acid?

Accepted Answer

$$\mathrm{CH_2O_2}$$

Chapter 2: The Chemical Context of Life – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard