An oxide or hydroxide that reacts with both acids and bases, as aluminum hydroxide does, is described as amphoteric.
Missing Word
amphoteric
An amphoteric substance can act as either an acid or a base. Aluminum hydroxide dissolves in acid to form Al3+ and in excess hydroxide to form a complex ion.
Category: Periodic Trends
Question 2
Different structural forms of the same element in the same physical state, such as O2 and O3, are called allotropes.
Missing Word
allotropes
Allotropes differ in how the atoms of one element are bonded. Oxygen has two allotropes, dioxygen and ozone, and carbon and phosphorus also have several.
Category: Carbon Allotropes
Question 3
A single layer of graphite, only one atom thick and an excellent conductor of heat and electricity, is called graphene.
Missing Word
graphene
Graphene is one sheet of sp2-bonded carbon atoms arranged in six-membered rings. Stacking many such sheets gives graphite, and rolling one gives a nanotube.
Category: Carbon Allotropes
Question 4
In diamond, each carbon atom is covalently bonded to four other carbon atoms in a rigid tetrahedral network.
Missing Word
diamond
Diamond's three-dimensional network of sp3-hybridized carbon atoms makes it extremely hard and an electrical insulator, unlike the layered graphite.
Category: Carbon Allotropes
Question 5
Aluminum is produced from bauxite, an ore made of impure aluminum oxide hydroxide.
Missing Word
bauxite
Bauxite is purified by dissolving it in hot sodium hydroxide, then reprecipitating aluminum hydroxide, which is heated to aluminum oxide for electrolysis.
Category: Metal Production
Question 6
Metalloids such as silicon conduct electricity less well than metals but better than nonmetals, so they are classified as semiconductors.
Missing Word
semiconductors
A semiconductor has electrical conductivity between that of a metal and an insulator. This property makes silicon and germanium the basis of transistors, computer chips and solar cells.
Category: Metalloids
Question 7
Most common rocks, soils, and clays are made of silicates, salts whose anions are built from SiO4 tetrahedra.
Missing Word
silicates
Silicates are built from SiO4 tetrahedra that share corners to form chains, sheets or three-dimensional frameworks. They make up much of Earth's crust and are the basis of many ceramics.
Category: Metalloids
Question 8
The only metalloid in group 13, which forms trigonal planar compounds that act as Lewis acids, is boron.
Missing Word
boron
Boron has three valence electrons, so its compounds such as BF3 and B(OH)3 have an incomplete octet and accept electron pairs. The other group 13 elements are metals.
Category: Metalloids
Question 9
The most common isotope of hydrogen, whose nucleus is a single proton with no neutrons, is called protium.
Missing Word
protium
Protium makes up nearly all natural hydrogen. Hydrogen is unusual in that each of its isotopes, protium, deuterium and tritium, has its own name.
Category: Hydrogen
Question 10
Industry combines nitrogen gas with hydrogen to make ammonia, a basic gas that is the starting material for many fertilizers.
Missing Word
ammonia
Ammonia, NH3, is made from atmospheric nitrogen and is the key raw material for fertilizers and nitric acid. A large share of all hydrogen produced is used for this purpose.
Category: Nitrogen and Phosphorus
Question 11
Certain microorganisms convert atmospheric N2 into compounds that living things can use with the help of an enzyme called nitrogenase.
Missing Word
nitrogenase
Nitrogenase is the enzyme that carries out biological nitrogen fixation, and it contains iron and molybdenum. Only certain microorganisms produce it, so most living things depend on them for usable nitrogen.
Category: Nitrogen and Phosphorus
Question 12
Elements of group 15, such as nitrogen and phosphorus, usually complete an octet by forming 3 covalent bonds.
Missing Word
3
Group 15 atoms have five valence electrons, so sharing 3 more electrons through 3 covalent bonds gives an octet, as in NH3 and PCl3.
Category: Nitrogen and Phosphorus
Question 13
The greenish-yellow halogen gas widely used to disinfect public water supplies is chlorine.
Missing Word
chlorine
Chlorine is a greenish-yellow gas made mainly by electrolysis of aqueous sodium chloride. It is used to disinfect water, bleach wood pulp and make PVC plastic.
Category: Halogens and Noble Gases
Question 14
A compound formed between two different halogens, such as ClF3 or IF7, is called an interhalogen.
Missing Word
interhalogen
In an interhalogen the heavier halogen is the central atom and is bonded to an odd number of lighter halogen atoms. These compounds are strong oxidizing agents.
Category: Halogens and Noble Gases
Question 15
The radioactive noble gas that can build up in tightly sealed buildings and raise the risk of lung cancer is radon.
Missing Word
radon
Radon forms from the decay of other radioactive elements in soil and rock. Because it is a gas, it can seep into basements and accumulate in poorly ventilated buildings.
Category: Halogens and Noble Gases