Question 1

Electrons whirl around the center of the atom at high speed, forming a(n)

Accepted Answer

Electrons do not follow a specific, predictable path, but instead occupy regions of space around the nucleus known as an electron cloud. The cloud represents the probability of finding an electron in a particular region at a particular time.

Question 2

The innermost electron shell in an atom holds up to ________ electrons.

Accepted Answer

The innermost electron shell of an atom, known as the K shell, can hold up to 2 electrons according to the 2n^2 rule, where n is the principal quantum number of the shell. For the K shell, n=1, so it can hold up to 2 electrons.

Question 3

The smallest stable units of matter are

Accepted Answer

Atoms are the smallest stable units of matter. They are made up of protons, neutrons, and electrons.

Question 4

If an isotope of oxygen has 8 protons, 10 neutrons, and 8 electrons, its mass number is

Accepted Answer

The mass number is calculated by adding the number of protons and neutrons in an atom. In this case, adding 8 protons and 10 neutrons gives a mass number of 18. Therefore, the correct answer is (C).

Question 5

Isotopes of an element differ in the number of

Accepted Answer

Isotopes of an element have the same number of protons in the nucleus, but different numbers of neutrons. This gives them the same atomic number but different atomic masses. The number of electrons in the nucleus and electron clouds may also vary, but this is not what defines an isotope.

Question 6

Radioisotopes have unstable

Accepted Answer

Radioisotopes have unstable nuclei, which means they have an excess of either protons or neutrons. This instability can lead to the emission of particles and/or energy in the form of radiation, which can be dangerous if not properly handled.

Question 7

By weight, which element is the second most abundant in the human body?

Accepted Answer

Carbon is the second most abundant element by weight in the human body, following oxygen. Oxygen makes up about 65% of the human body weight, while carbon accounts for about 18%.

Question 8

By weight, which element is the most plentiful in the human body?

Accepted Answer

Oxygen is the most plentiful element in the human body by weight, making up approximately 65% of the body's total weight. It is a key component of water and many organic molecules that make up the body, including carbohydrates, proteins, and lipids.

Question 9

Given the following approximate values, calculate the molecular weight for NaCl. Atomic number for Na: 11, Atomic weight for Na: 23 g/mol, Atomic number for Cl: 17,Atomic weight for Cl: 35 g/mol, Boiling point for Cl: -34 °C

Accepted Answer

NaCl is composed of one sodium (Na) atom and one chlorine (Cl) atom. To calculate the molecular weight, we add the atomic weights of both atoms together:

23 g/mol (Na) + 35 g/mol (Cl) = 58 g/mol (NaCl)

Therefore, the correct answer is E.

Question 10

The "atomic weight" of an atom reflects the average number of

Accepted Answer

Atomic weight is the sum of the number of protons and neutrons in an atom's nucleus, as electrons contribute very little to the mass of an atom.

Question 11

One mole of any element has the same

Accepted Answer

One mole of any element contains Avogadro's number of atoms (approximately 6.022 x 10^23 atoms), which is a constant for all elements, making the number of atoms the same for one mole of any element.

Question 12

In any given molecule, the sum of the atomic weights of its component atoms is called

Accepted Answer

The answer of In any given molecule, the sum of...

Question 13

Which of these lists contains only trace elements?

Accepted Answer

Trace elements are those required by an organism in only minute quantities. Silicon, fluorine, and tin fit this description, whereas the elements listed in the other options are either too abundant in organisms (e.g., oxygen, carbon, calcium) or not universally considered trace elements.

Question 14

The nucleus of an atom consists of

Accepted Answer

The nucleus of an atom consists of protons and neutrons, which are collectively called nucleons. Electrons are located outside the nucleus in the electron cloud. Protons have a positive charge, while neutrons have no charge. The number of protons in the nucleus determines the atomic number and identity of the element, while the total number of protons and neutrons determines the atomic mass.

Question 15

Which element commonly has only a proton as its nucleus?

Accepted Answer

Hydrogen is the element that commonly has only one proton in its nucleus, making it the simplest and lightest element on the periodic table.

Question 16

________ is a pure substance composed of atoms of only one kind.

Accepted Answer

The answer of ________ is a pure substance composed of...

Question 17

The center of an atom is called the

Accepted Answer

The correct term for the center of an atom is the nucleus.

Question 18

The "atomic number" of an atom is determined by the number of ________ it has.

Accepted Answer

The atomic number of an atom is equal to the number of protons it has in its nucleus. This number determines which element the atom represents.

Question 19

If an element is composed of atoms with an atomic number of 6 and a mass number of 14, then a non-isotopicatom of this element contains

Accepted Answer

The answer of If an element is composed of atoms...

Question 20

Helium (HE) has an atomic number of 2. It is chemically stable because it

Accepted Answer

Helium has two electrons, filling its only electron shell. It does not need to gain or lose any electrons to achieve stability, and as such, it is chemically inert.

Quiz 2: The Chemical Level of Organization