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chem > chap 4 and 5 > Flashcards

chap 4 and 5 Flashcards

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1
Q

what are noble gases?

A

noble gases are element in the rightmost group of the periodic table. they all have full valence shells and have noble gas configuration. hence, noble gases are chemically unreactive. they are monoatomic and exist as simple atoms

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2
Q

how does a cation form?

A

metal atom loses electrons to form positive ion

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3
Q

how does an anion form?

A

non-metal atom gains electrons to form negative ion

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4
Q

how does an ionic bond form?

A

when a metal reacts with non-metal, one or more valence electrons is / are transferred from a metal atom to a non-metal atom

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5
Q

what are ionic bonds?

A

ionic bonds are the strong electrostatuc forces of attraction between oppositely-charged ions

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6
Q

what is the formula for zinc?

A

Zn^2+

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7
Q

what is the formula for silver>

A

Ag^+

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8
Q

what is the formula for ammonium?

A

NH₄⁺

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9
Q

what is the formula for ammonia?

A

NH3

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10
Q

what is the formula for methane?

A

CH₄

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11
Q

what is the formula for hydroxide?

A

OH¯

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12
Q

what is the formula for nitrate?

A

NO3^-

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13
Q

what is the formula for sulfite?

A

SO₃²⁻

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14
Q

what is the formula for sulfate?

A

SO₄²-

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15
Q

what is the formula for phosphate?

A

PO₄³⁻

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16
Q

what is the formula for carbonate?

A

CO3^2-

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17
Q

what are polyatomic ions?

A

they are ions composed of two or more covalently bonded atoms. compounds formed from these ions have both covalent and ionic bonding.

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18
Q

what are the structural properties of ionic substances?

A

ionic compounds have giant ionic crystal lattice structures. the lattice consists of large number of alternating positive and negative ions held together by strong electrostatic forces of attraction

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19
Q

do ionic compounds have low or high melting and boiling points?

A

they have high melting and boiling points. ionic compounds are typically solids at room temperature. ionic compounds have a large giant ionic structure. large amounts of energy is needed to overcome the strong forces of attraction between oppositely charged ions

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20
Q

are ionic compounds hard?

A

ionic compounds are hard but brittle. the strong electrostatic forces of attraction between oppositely charge ions makes ionic compounds resistant to deforming. hence, ionic compounds tend to be hard
when enough force is applied , the ions move away from their lattice positions and ions of the same charge approach each other. the repulsive forces between ions of the same charge becomes larger than the attractive forces. the ionic structure is deformed and the structure shatters

21
Q

are ionic compound soluble in water?

A

most are soluble in water, insoluble in organic solvents. water molecules are attracted to the ions. this weakens the electrostatic forces of attraction between oppositely charged ions. hence, the ions are pulled from the lattice structure and the compound dissolves to form an aqueous solution

22
Q

can ionic compounds conduct electricity?

A

ionic compounds can conduct electricity in the molten and aqueous state. in the solid state, the ions in the lattice can only vibrate about their fixed positions. hence the ions are immobile and there are no mobile ions to conduct electricity. in aqueous or molten state, the ions are free to move about. hence the mobile ions enable the ionic compounds to conduct electricty.

23
Q

how are covalent bonds formed?

A

covalent bonds are formed when electrons are shared between atoms of non-metals

24
Q

what are the structural properties of molecules with simple molecular structure?

A

atoms in the molecule are held together by strong covalent bonds. however, the molecules are held together by weak intermolecular forces of attraction

25
Q

does simple molecules have low or high melting and boiling point?

A

molecules with simple molecular structure evaporate easily and are described as volatile. they exist mostly as gases or liquids at room temperature.
these molecules have simple molecular structure. small amount of energy is needed to overcome the weak intermolecular forces of attraction
the size of the molecule will affect the melting and boiling point. as the molecule gets larger, the intermolecular forces of attraction are stronger and hence more energy is required to overcome them. hence, larger molecules have higher melting and boiling points than smaller molecules

26
Q

are simple molecules soluble in water?

A

insoluble in water but soluble in organic solvents e.g. alcohol, acetone, benzene

27
Q

can simple molecules conduct electricity?

A

most substances with simple molecular structure exist as molecules and do not have mobile ions or electrons to conduct electricity
some substances might dissociate in water to form aqueous solutions that can conduct electricity, for example, hydrogen chloride gas dissolving in water to form hydrochloric acid (presence of mobile H+ and cl- ions)

28
Q

what is the arrangement of atoms in diamond?

A

each carbon atom forms covalent bonds with four other carbon atoms. diamond has a three-dimensional network structure in a tetrahedral structure

29
Q

what is the arrangement of atoms in graphite ?

A

each carbon atom forms covalent bonds with three other carbon atoms. graphite has a layered structure consisting of hexagonal rings of carbon atoms

30
Q

what are allotropes?

A

allotropes are different forms of the same element with different structural arrangements of atoms

31
Q

what are the structural properties of molecules with giant covalent structure?

A

molecules with giant covalent structure have numerous covalent bonds holding many atoms together, making them very rigid and able to withstand large forces (e.g. diamond)

32
Q

what are the structural properties of graphite?

A

graphite’s structure consists of strong covalent bonds between atoms within each layer, but weak intermolecular forces of attraction between the layers of carbon. hence, layer of carbon atoms can slide past each other , but each layer is hard to break apart

33
Q

are giant covalent substances hard?

A

diamond is hard and is often used to coat drill bits and cutting tools. giant covalent structures are hard. large amount of energy is needed to break the strong covalent bonds between atoms in diamond
graphite is soft and slippery, and is used in solid lubricant and pencil lead. small amount of energy is needed to overcome the weak intermolecular forces of attraction between layers of carbon atoms. the layers of carbon atoms can slide over each other easily

34
Q

do giant covalent substances have a higher or lower melting and boiling points?

A

molecules with giant covalent structure are very resistant to heat and are solids at room temperature. the molecules have giant covalent structure. large amount of energy is needed to break the strong covalent bonds between atoms

35
Q

are giant covalent substances soluble in water?

A

insoluble in water and organic solvents

36
Q

are giant covalent substances conductors of electricity?

A

molecules with giant covalent structure, like diamond and silicon dioxide, have no mobile electrons or mobile ions and hence do not conduct electricity. however, in graphite, each carbon atom is bonded to three pother carbon atoms. this leaves one unbonded delocalised electron per carbon atom. hence the presence of mobile electrons allow graphite to conduct electricity

37
Q

what is metallic bonding?

A

metal atoms are held strongly together by metallic bonding. in the solid state, metal atoms are closely packed in an orderly manner. these atoms form a giant metallic lattice structure. the metal atoms lose their outermost electrons to become positively-charged ions (cations). the electrons are now said to be delocalised. the delocalised mobile electrons can move around freely between the metal cations

38
Q

what are metallic bonds?

A

metallic bonds are the strong electrostatic forces of attraction between positively-charged ions (cations) in the metal and “sea of delocalised mobile electrons”

39
Q

metals are malleable and ductile. define the terms malleable and ductile.

A

malleable: can be hammered, bent and flattened into a thin sheet
ductile: can be pulled into a wire without breaking

40
Q

why are metals malleable and ductile?

A

pure metals have a regular structure. if enough force is applied, the layers of atom can slide over one another easily, without disrupting the metallic bonding

41
Q

why are metals malleable and ductile?

A

pure metals have a regular structure. if enough force is applied, the layers of atom can slide over one another easily, without disrupting the metallic bonding

42
Q

do metals have a higher or lower melting and boiling point?

A

metals have a high melting and boiling point. metals are typically solids at room temperature and pressure. metals have a giant metallic lattice structure. large amount of energy is needed to overcome the strong electrostatic forces of attraction between positively-charged ions and “sea of delocalised mobile electrons”

43
Q

are metals good conductors of heat?

A

metals are good conductors of heat. in the metallic lattice, the ions are closely packed. the proximity of the ions allow them to transfer heat energy by vibration quickly from one ion to another. the movement of mobile electrons further speed up the rate of transfer of heat. hence, metals are good conductors of heat

44
Q

can metal conduct electricity?

A

metals conduct electricity in molten and solid state. in solid or molten state, the electrons are free to move about. hence the mobile electrons enable metals to conduct electricity

45
Q

what are alloys?

A

an alloy is a mixture of a metal with one or more other elements. the elements can be metals or non-metals

46
Q

list two examples of alloys

A

brass (copper and zinc)
stainless steel (iron, chromium nickel and carbon)

47
Q

what are alloys used for?

A

-to improve the appearance of metals
-make metals harder and stronger
-lower the melting points of metals: alloys are mixtures that melts over a range of temperatures
-make metals more resistant to corrosion

48
Q

are alloys strong and hard or weak and soft?

A

compared to pure metals which are soft as the layers of atoms that are orderly arranged can slide over each other easily, alloys are harder and stronger. in alloys, the additional metal / non-metal atoms of different sizes disrupts the orderly arrangement of atoms in the pure metal, making it difficult for layers of atom to slide over one another. this makes alloys much stronger and harder

chem (8 decks)

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