Question 1

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Based on this information, which of the following is also true of molybdenum?

Accepted Answer

The number of neutrons in an atom is calculated by subtracting the atomic number (number of protons) from the mass number. For molybdenum with an atomic number of 42 and mass numbers ranging from 92 to 100, the number of neutrons would range from 50 (92-42) to 58 (100-42). Choices B, C, and D are incorrect because the number of protons (and thus electrons in a neutral atom) in molybdenum is constant (42), and isotopes differ in the number of neutrons, not electrons.

Question 2

How many electrons are present in the neutral atom represented in the Periodic Table block in the figure?

Accepted Answer

C

Question 3

What element does not react with other elements?

Accepted Answer

Helium is a noble gas, which means it is very stable and does not easily react with other elements due to its full valence electron shell.

Question 4

Atoms have no electric charge because they have ________.

Accepted Answer

Atoms are neutral because they contain an equal number of positively charged protons and negatively charged electrons, which balance each other out.

Question 5

A neutral atom has 2, 8, 8 electrons in its first, second, and third energy levels. This information ________.

Accepted Answer

The atomic mass of an element is determined by the number of protons and neutrons in its nucleus, not by the electron configuration.

Question 6

Which of the following statements is TRUE?

Accepted Answer

Some naturally occurring elements, such as mercury, lead, and arsenic, can be toxic to organisms even in relatively low concentrations. This toxicity can affect various biological processes and lead to health issues.

Question 7

An ion that consists of 7 protons, 6 neutrons, and 11 electrons has a net charge of ________.

Accepted Answer

The ion has 7 protons (positive charges) and 11 electrons (negative charges). The net charge is calculated as the difference between the number of protons and electrons: 7 - 11 = -4, so the ion has a net charge of 4-.

Question 8

Which pair of elements is most likely to react if bought together?

Accepted Answer

Sodium and chlorine react vigorously to form sodium chloride (table salt), as sodium is a highly reactive alkali metal and chlorine is a reactive halogen.

Question 9

What is the atomic number of the neutral atom represented by the Periodic Table block in the figure?

Accepted Answer

The answer of  What is the atomic number of...

Question 10

Which of the following has the smallest total mass?

Accepted Answer

Electrons have a significantly smaller mass compared to neutrons and protons, making two electrons have the smallest total mass among the options.

Question 11

How many electrons are present in a H- and H+ ion respectively?

Accepted Answer

A hydrogen atom typically has one electron. In a H- ion, an extra electron is added, making it 2 electrons. In a H+ ion, the single electron is removed, leaving it with 0 electrons.

Question 12

How many electrons are present in the +2 ionic form of the atom in the Periodic Table block shown in the figure?

Accepted Answer

The answer of  How many electrons are present in...

Question 13

Which of the following best explain why argon, which is a noble gas, does not react with other elements. Noble gases ________.

Accepted Answer

Noble gases like argon have completely filled valence electron shells, which makes them chemically stable and unreactive. This full outer shell configuration is energetically favorable and does not easily allow for the gain or loss of electrons, thus preventing reactions with other elements.

Question 14

An ion with six protons, seven neutrons, and a charge of 2+ has an atomic number of ________.

Accepted Answer

The atomic number is determined by the number of protons in an atom, which in this case is six.

Question 15

Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by all forms of life?

Accepted Answer

Iron is a trace element essential for all forms of life because it plays a critical role in processes such as oxygen transport, DNA synthesis, and electron transport in mitochondria.

Question 16

The atomic number of nitrogen is 7. Which of the following explains the greater mass number of nitrogen-15 compared to nitrogen-14? Nitrogen-15 contains ________.

Accepted Answer

The mass number of an isotope is the sum of its protons and neutrons. Since nitrogen's atomic number is 7 (indicating 7 protons), the difference in mass number between nitrogen-15 and nitrogen-14 must be due to the difference in the number of neutrons. Nitrogen-15 has 8 neutrons (15 - 7 = 8) and nitrogen-14 has 7 neutrons (14 - 7 = 7).

Question 17

About 25 of the 92 natural elements are known to be essential to life. Four of these 25 elements make up approximately 96% of living matter. Which of the following elements account for most of the remaining 4% of an organism's mass?

Accepted Answer

The four elements that make up approximately 96% of living matter are carbon, oxygen, hydrogen, and nitrogen. Therefore, the elements that account for most of the remaining 4% of an organism's mass include calcium, potassium, phosphorus, and sulfur, as these are essential for various biological processes but are present in smaller amounts compared to the primary four.

Question 18

Which of the following is true of oxygen that has 8 protons, 8 neutrons, and 8 electrons?

Accepted Answer

Oxygen with 8 protons, 8 neutrons, and 8 electrons has an atomic number of 8, as the atomic number is determined by the number of protons.

Question 19

Which of the following atoms has the smallest number of neutrons?

Accepted Answer

Nitrogen-14 has 7 protons and 14 - 7 = 7 neutrons, which is the smallest number of neutrons among the options listed.

Question 20

Which of the following are compounds?

Accepted Answer

Compounds are substances formed from two or more different elements chemically bonded together. H₂O (water) and CH₄ (methane) are compounds, while O₂ (oxygen) is a molecule of a single element.

Quiz 2: Atoms and Molecules