Chemistry 101: Chapter 2/3: Atoms, Ions, And Molecules; Stoichiometry

Gold and Helium are both elements, Ethanol is a molecular compound, and Sodium Chloride is an ionic compound.

J.J. Thompson is credited with the discovery of electrons in 1897 through his experiments with cathode rays.

Robert Millikan's famous oil-drop experiment in 1909 provided the first accurate measurement of the charge of an electron, from which he was able to calculate the mass of an electron. This experiment was integral in determining key properties of subatomic particles.

The Plum-pudding Model suggests that electrons (e-) are distributed throughout a diffuse, positively charged sphere, unlike the incorrect answers provided.

Henri Becquerel discovered invisible radiation, consisting of charged particles, which led to the development of the field of nuclear physics.

Radioactivity refers to the spontaneous emission of high energy radiation and particles, such as Beta and Alpha particles, from the nucleus of an unstable atom.

Beta particles are high energy electrons while alpha particles have a +2 charge and a mass equal to a helium nucleus. Therefore, the correct answer is the one that highlights these characteristics accurately.

The gold foil experiment was conducted by Rutherford to test Thompson's model of the atom, which eventually led to the discovery of the atomic nucleus.

James Chadwick discovered the neutron by bombarding a thin sheet of beryillium with alpha particles.

The nucleus of an atom is the positively charged center where most of the mass is concentrated, consisting of protons and neutrons. The other options do not accurately describe the nucleus.

Protons and neutrons are the two main subatomic particles that make up the nucleus of an atom. Electrons are found in the electron cloud surrounding the nucleus. Photons are particles of light and are not found within the nucleus. Mesons are subatomic particles that do play a role in the strong nuclear force, but they are not part of the nucleus of an atom.

Distances within a nucleus are typically measured in picometers due to the extremely small size of atomic nuclei.

The correct answer defines AMU as a unit for expressing relative masses of atoms and subatomic particles, not temperature, length, or counting atoms.

The measurement 'Dalton' was named for the English chemist John Dalton, who is known for his work in the development of modern atomic theory. Therefore, the correct answer is that it was named after John Dalton.

Neon has three different isotopes: Neon-20, Neon-21, and Neon-22.

Aston is known for proposing the theory of isotopes, which revolutionized our understanding of atomic structure and elements.

The mass number (A) encompasses both protons and neutrons in the nucleus, providing a measure of the total nucleons present.

Elemental symbols in chemistry are used to represent elements on the periodic table, helping to distinguish between different types of atoms. These symbols are typically one or two letters long and are unique to each element.

The atomic number (Z) specifically refers to the number of protons in the nucleus of an atom, which is a fundamental property that uniquely identifies the element. It does not directly involve the number of neutrons, electrons, or the mass number of the atom.

Most elements have multiple isotopes due to differing numbers of neutrons in their nuclei.

The correct format for isotopic symbols is to write the element symbol followed by the mass number. This helps to represent the specific isotope of an element.

The Average Atomic Mass is a weighted average that takes into account the natural abundance of each isotope of an element, not just the sum of masses or the mass of the most abundant isotope. It is a comprehensive calculation involving all isotopes present.

Natural abundance specifically refers to the proportion of a particular isotope in relation to all isotopes for an element in a natural sample, not just the amount of an element found in nature.

Mercury has a total of 7 isotopes with the masses 196, 198, 199, 200, 201, 202, and 204. Each isotope has a specific number of protons and neutrons within its nucleus, resulting in different atomic masses and properties.

Dmitri Mendeleev's major contributions in 1872 were the organization of elements in the periodic table based on atomic mass and properties, along with leaving gaps for undiscovered elements.

The Periodic Table is organized in horizontal rows and vertical columns, with elements in the same group sharing similar properties. It also categorizes elements into metals, nonmetals, and metalloids.

Metals are known for their shiny appearance, ability to conduct heat and electricity, as well as being malleable and ductile. The incorrect answers provided describe properties that are not typically associated with metals.

Nonmetals can exist in solids, liquids, and gases, unlike metals which are typically solid. Plasma and superfluids are not typically associated with nonmetals.

Metalloids exhibit properties that are a mixture of metals and nonmetals, making them important elements in the periodic table.