Q: Which equation correctly calculates the number of neutrons in an atom?

$$\text{Number of neutrons} = \text{Atomic mass} - \text{Atomic number}$$

Question 1

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

Accepted Answer

Oxygen is more electronegative than hydrogen, resulting in an unequal distribution of electrons and a bent molecular shape.

Question 2

Which equation correctly calculates the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{Atomic mass} - 	ext{Atomic number}$$

Question 3

Carbon-14 is used in radiometric dating because it is radioactive. What makes an isotope radioactive?

Accepted Answer

It has an unstable nucleus due to an excess of neutrons, causing it to emit particles or energy.

Question 4

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

Accepted Answer

All compounds are molecules, but not all molecules are compounds.

Question 5

Which of the following elements is most likely to form ionic bonds with sodium (Na)?

Accepted Answer

Chlorine (Cl), because it has a high electronegativity and needs one electron to complete its valence shell.

Question 6

Which statement about isotopes is correct?

Accepted Answer

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

Question 7

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

Accepted Answer

Their valence electron shells are full, making them stable and unlikely to react.

Question 8

Which of the following is a correct Lewis dot diagram for a carbon atom?

Accepted Answer

A carbon atom with four dots around the symbol 'C', representing its four valence electrons.

Question 9

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 10

Which of the following molecules is NOT classified as a compound?

Accepted Answer

$$O_2$$, because it consists of two atoms of the same element.

Question 11

Which property of water is most directly responsible for its ability to dissolve many ionic compounds?

Accepted Answer

Its polarity, which allows it to surround and separate ions.

Question 12

Which of the following best explains the role of buffers in biological systems?

Accepted Answer

Buffers help maintain a stable pH by absorbing excess hydrogen or hydroxide ions.

Question 13

Which equation correctly relates pH to the concentration of hydrogen ions in solution?

Accepted Answer

$$	ext{pH} = -\log_{10}[H^+]$$

Question 14

Which of the following best describes the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity, while nonpolar covalent bonds involve equal sharing.

Question 15

Which of the following is an example of an allotrope?

Accepted Answer

Diamond and graphite, which are different forms of carbon.

Question 16

Which of the following best explains why the shape of a molecule like water is important for its function?

Accepted Answer

The bent shape of water creates a dipole moment, making it polar and allowing it to form hydrogen bonds.

Question 17

Which of the following best describes the relationship between atomic number and chemical properties?

Accepted Answer

The atomic number determines the number of protons, which defines the element and its chemical behavior.

Question 18

Which of the following is true about the energy levels of electrons in an atom?

Accepted Answer

Electrons in higher energy levels are farther from the nucleus and have more potential energy.

Question 19

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

Accepted Answer

Carbon-14 dating is used to determine the age of ancient biological samples.

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

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