Ch. 2 (Atoms, Ions, and Molecules)

Briefly explain the discovery of electrons.

During an experiment that researched how gases conduct electricity, cathode rays (streams of electricity) were discovered to be deflected if the site of beam transmission had an opposite charge.

Explain the mass-to-charge ratio of a particle.

It is equal to the mass of an ion divided by its electric charge. It is the same for every given type of particle.

Explain the difference between alpha and beta particles.

• Alpha particles are emitted during radioactive decay and are essentially the mass and charge to the nucleus of helium-4. They carry a positive charge.

• Beta particles are emitted during radioactive decay and are equivalent in mass and charge to a high-energy electron. They were found to penetrate materials best.

Explain the array structure of the periodic table.

• In order of increasing atomic number, rows are called periods and columns are called groups.

• All the elements with atomic numbers above 83 are highly radioactive.

Explain the properties of three major categories of the periodic tables.

• Metals tend to conduct heat and electricity well, are malleable, and ductile; all but mercury are solid at room temperature.

• Nonmetals are poor conductors and most are gases at room temperature; the solids among them, like iodine, are brittle.

• Metalloids are both; they have the physical properties of metals but the chemical properties of nonmetals.

How are the ion numberings arranged in the periodic table?

• Group one, two, three, and four commonly form 1+, 2+, 3+ and 4+ monoatomic ions, respectively.

• Groups 15, 16, and 17 form monoatomic ions with charges of 3-, 2-, and 1-, respectively.

Explain the specific chemical groups of the periodic table.

• Elements with atomic numbers 58 to 71 are called the lanthanides, all of which have radioactive isotopes.

• Group 1 elements are called alkali metals (except hydrogen) because they form alkaline solutions upon reacting with water.

• Group 17 elements are called halogens and form most salts and ionic compounds.

• Group 2 elements are called alkaline earth metals and form ionic bounds with halogens.

Explain the cation-to-anion ratio.

• Alkaline earth metals that bond with halogens from group 17 have a ratio of 1:2 cations to anions since one 2+ charge needs two 1- charges to be stable.

• Based on this similar principle, an alkaline earth metal that bonds with a halogen from group 16 has a ratio of 1:1 cations to anions since one 2+ charge needs only one 2- charge to neutralize.