Section 11.8- Important Semimetals and Their Compounds

Question 1

the second most abundant element in earth’s crust

Answer 1

silicon

Question 2

silicon does not occur free but rather as

Answer 2

silicates

Question 3

the most common form of silicon is in

Answer 3

mineral silicates

Question 4

semimetal that is not very common, occurring primarily as the sulfide along with other metal sulfide ores

Answer 4

germanium

Question 5

electrical conductivity intermediate between conductors and insulators

Answer 5

semiconductor properties

Question 6

silicon and germanium’s ___________________ make them well-suited for use in devices such as transistors and diodes

Answer 6

semiconducting properties

Question 7

silicon is produced by

Answer 7

heating silica with coke to a very high temperature in an electric furnace

Question 8

the silicon produced is about 98% pure and is suitable for use as an

Answer 8

alloying element in aluminum alloys and spring steel

Question 9

one of the most important uses of silicon is in the

Answer 9

manufacture of computer chips and other electronic devices

Question 10

to be suitable for chipmaking, silicon must be further purified by first reacting it with gaseous hydrogen chloride to form

Answer 10

trichlorosilane

Question 11

more complex polyanion chains are found in substances like

Answer 11

asbestos

Question 12

most silicates consist of repeating units of Si)4 tetrahedrons, each sharing one or more oxygen atoms with other tetrahedrons to form

Answer 12

polyanions

Question 13

3D network or polymers of silicates in which all four oxygen atoms are shared between tetrahedrons are called

Answer 13

silica

Question 14

the most common crystalline form of silica is

Answer 14

sand or granulated quartz

Question 15

silicates in which some of the silicon atoms are replaced by aluminum atoms are known as

Answer 15

aluminosilicates

Question 16

when silica is melted, it does not return to its crystalline structure when it cools; rather, it assumes an amorphous or noncrystalline state known as ______________, which is transparent and solid

Answer 16

glass

Question 17

glass made of pure silica is called _____________________ and is used in halogen light bulbs

Answer 17

fused silica or fused quartz

Question 18

heat-resistant glass that does not expand and contract a great deal with temperature changes is known as

used in cookware and laboratory equipment

Answer 18

borosilicate glass
aluminosilicate glass

Question 19

one of th most controversial kinds of silicates is ________________, a natural polysilicate mineral formed by heat and pressure within the earth’s crust

Answer 19

asbestos

Question 20

the most commonly used form of asbestos is

Answer 20

chrysotile or white asbestos

Question 21

chrysotile is a fibrous form of a rock called

Answer 21

serpentine

Question 22

a relatively rare element, with some large deposits found in the US and Asia

Answer 22

boron

Question 23

one of the most common boron compounds is the mineral

Answer 23

borax

Question 24

uses of boron

Answer 24

laundry detergents
fire retardants
insecticides
fertilizers

Question 25

one of the hardest materials known, having almost identical properties to diamonds

Answer 25

boron nitride