In Dalton's atomic theory, all atoms of a given element are identical in mass and other properties.
Correct Answer
True
True. This was one of Dalton's postulates. It was later revised when isotopes were discovered, since atoms of one element can differ in mass.
Category: Early Atomic Theory
Question 2
An electron has about the same mass as a proton.
Correct Answer
False
False. An electron is far lighter, with roughly 1/1800 of the mass of a proton. Almost all of an atom's mass comes from its protons and neutrons.
Category: Atomic Structure
Question 3
A proton and a neutron each have a mass of about 1 amu.
Correct Answer
True
True. Protons and neutrons have nearly equal masses, each slightly more than 1 amu. That is why an atom's mass in amu is close to its mass number.
Category: Atomic Structure
Question 4
Electrons are located inside the nucleus along with the protons and neutrons.
Correct Answer
False
False. Electrons occupy the region around the nucleus, and that region makes up nearly all of an atom's volume. Only protons and neutrons are found in the nucleus.
Category: Atomic Structure
Question 5
A neutral atom has equal numbers of protons and electrons.
Correct Answer
True
True. Each proton carries a 1+ charge and each electron a 1- charge, so equal numbers give a net charge of zero. An ion forms when these numbers become unequal.
Category: Atomic Structure
Question 6
A cation forms when an atom gains one or more electrons.
Correct Answer
False
False. A cation is a positive ion, formed when an atom loses electrons. Gaining electrons produces a negative ion, an anion.
Category: Atomic Structure
Question 7
The mass number of an atom is the total number of protons and neutrons in its nucleus.
Correct Answer
True
True. The mass number counts all the nucleons, protons plus neutrons. The atomic number counts only the protons.
Category: Atomic Structure
Question 8
In the modern periodic table, the elements are arranged in order of increasing atomic mass.
Correct Answer
False
False. The modern table arranges elements by increasing atomic number. Mendeleev's early table was based on atomic mass, but strict mass order puts a few pairs, such as tellurium and iodine, in the wrong groups.
Category: The Periodic Table
Question 9
Elements in the same group of the periodic table have similar chemical properties.
Correct Answer
True
True. Elements in a vertical column behave alike chemically; for example, sodium and potassium both react vigorously with water. This repeating pattern is the basis of the periodic table.
Category: The Periodic Table
Question 10
The noble gases are found in group 1 of the periodic table.
Correct Answer
False
False. The noble gases, such as helium, neon and argon, are in group 18. Group 1 holds hydrogen and the alkali metals.
Category: The Periodic Table
Question 11
Hydrogen gas is made of diatomic molecules with the formula H2.
Correct Answer
True
True. Elemental hydrogen exists as molecules of two bonded atoms. Nitrogen, oxygen and the halogens also exist as diatomic molecules.
Category: Chemical Formulas
Question 12
Most of the elements on the periodic table are nonmetals.
Correct Answer
False
False. Most elements are metals, which lie mostly to the left of the stair-step line on the table. Nonmetals are found in the upper right portion.
Category: The Periodic Table
Question 13
Molecular compounds are usually formed from two or more nonmetals.
Correct Answer
True
True. Nonmetal atoms share electrons in covalent bonds to form discrete molecules, as in water and carbon dioxide. Compounds of a metal and a nonmetal are usually ionic.
Category: Ionic and Molecular Compounds
Question 14
In an ionic compound such as NaCl, the atoms share electrons in covalent bonds.
Correct Answer
False
False. In NaCl, sodium transfers an electron to chlorine, and the resulting Na+ and Cl- ions are held together by electrostatic attraction. Electron sharing describes covalent bonds in molecular compounds.
Category: Ionic and Molecular Compounds
Question 15
The formula of the ionic compound formed from aluminum and oxygen is Al2O3.
Correct Answer
True
True. Aluminum forms Al 3+ and oxygen forms O 2-, and two Al 3+ ions (6+) balance three O 2- ions (6-). An ionic formula always has a net charge of zero.
Category: Ionic and Molecular Compounds
Question 16
The sulfate ion has the formula SO3 2-.
Correct Answer
False
False. Sulfate is SO4 2-. The ion SO3 2-, with one fewer oxygen atom, is sulfite.
Category: Chemical Nomenclature
Question 17
The ionic compound CaCO3 is named calcium carbonate.
Correct Answer
True
True. An ionic compound is named cation first, then anion; Ca 2+ is calcium and CO3 2- is the polyatomic carbonate ion. No Roman numeral is needed because calcium forms only one charge.
Category: Chemical Nomenclature
Question 18
Greek prefixes such as di- and tri- are used in the names of ionic compounds such as MgCl2.
Correct Answer
False
False. MgCl2 is named magnesium chloride without prefixes, because the ion charges fix the ratio. Greek prefixes are used for binary molecular compounds, such as carbon dioxide.
Category: Chemical Nomenclature
Question 19
An aqueous solution of HCl is named hydrochloric acid.
Correct Answer
True
True. A binary acid in water is named with the prefix hydro-, the root of the nonmetal and the suffix -ic, followed by acid. Pure gaseous HCl is called hydrogen chloride.
Category: Chemical Nomenclature
Question 20
An oxyacid whose anion ends in -ate is named with the suffix -ous followed by acid.
Correct Answer
False
False. An -ate anion gives an -ic acid, as sulfate gives sulfuric acid and nitrate gives nitric acid. The -ous ending is used for acids from -ite anions, such as nitrous acid from nitrite.
Category: Chemical Nomenclature