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Chemistry IGCSE > Atoms, elements and compounds > Flashcards

Atoms, elements and compounds Flashcards

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1
Q

Define an element

A

substance made up of atoms that that all contain the same amount of protons
substance that can no longer be divided

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2
Q

Define a mixture

A

combination of two or more substances that are NOT chemically combined
Mixtures can be seperated by physical methods

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3
Q

Define a compound

A

pure substance of two or more elements chemically combined
they can’t be seperated back to their orginal elements by physical means

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4
Q

Difference between mixture and compound

A

mixture isn’t chemically combined and physical methods can be used to separate the elements inside whereas in the compound the elements are chemically combined and it’s not possible to separate them by physical means.
Compounds also have a sharp and specific bp and mp whereas mixtures will boil in a range of temperatures

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5
Q

a substance is pure if…

A

it has a sharp, specific boiling point, and melting point
if it is completely made up of a single element or a compound

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6
Q

What are the subatomic particles of an atom

A

electron
proton
neutron

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7
Q

Describe the structure of the atom

A

central nucleus containing neutrons and protons
surrounded by electrons in shells

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8
Q

What subatoms are located in the nucleus of an atom?

A

Protons and neutrons

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9
Q

What subatom is found in the shells of an element

A

electrons

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10
Q

What is the relative atomic mass of a proton

A

1

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11
Q

What is the relative atomic mass of a neutron

A

1

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12
Q

What is the relative atomic mass of an electron

A

0.005

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13
Q

Define proton number/ atomic number

A

number of protons in the nucleus of an atom

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14
Q

Define mass number/nucleon number

A

total number of protons and neutrons in the
nucleus of an atom

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15
Q

number of outer shell electrons is equal
to…?

A

the group number in Groups I to VII

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16
Q

the number of occupied electron shells is equal to…?

A

equal to the period number

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17
Q

What is the relative charge of a proton

A

+1

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18
Q

What is the relative charge of a neutron

A

0

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19
Q

What is the relative charge of an electron

A

-1

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20
Q

Number of protons in an element equal to what?

A

number of electrons

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21
Q

How can you calculate the number of neutrons in an element?

A

nucleon/mass number MINUS proton number

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22
Q

EASY TIP!!!!

A

MASS= MASSIVE, mass number is ALWYAS the bigger one

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23
Q

How to calculate the mass number of an element?

A

number of neutrons+ number of protons

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24
Q

What determines which element one is?

A

the atomic number of an atom and ion

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25
Q

maximum capacity of electrons the first shell can hold

A

2

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26
Q

maximum capacity of electrons the second shell can hold

A

8

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27
Q

maximum capacity of electrons the third shell can hold

A

8

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28
Q

Define the term isotope

A

different atoms of the same
element that have the same number of protons
but different numbers of neutrons

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29
Q

What is an ion?

A

ELECTRICALLY CHARGED atom or group of atoms formed by the loss or gains of electrons

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30
Q

Do isotopes of the same element have the same chemical properties?

A

isotopes of the same element have
the same chemical properties because they have
the same number of electrons and therefore the
same electronic configuration

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31
Q

Where does the loss or gain of electrons take place in?

A

outer most shell

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32
Q

Explain the ionisation of metals or formation of cations

A

all metals can loose electrons to other atoms to become positive ions known as CATIONS

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33
Q

Explain the ionisation of non-metals or formation of cations

A

all non metals can gain electrons from other atoms to become negatively charged ions, known as ANIONS

34
Q

State what an ionic bond is

A

a strong electrostatic attraction between oppositely charged ions that keep ionic compounds together

35
Q

How are ionic compounds formed? Explain

A

when metals react with non-metals
Metals loose one of their outermost electrons and non-metals GAIN to form positive and negative ions

36
Q

What are positive and negative ions hold together by?

A

electrostatic forces of attractions between opposite charges

37
Q

Describe the giant lattice structure of ionic
compounds

A

regular arrangement of alternating positive and negative ions

38
Q

How is the lattice structure of ionic compounds?

A

GIANT, has regular arrangement of alternating positive and negative ions

39
Q

What is formed when when metal atoms and non-metal atoms react?

A

Ionic compounds

40
Q

Describe the properties of ionic compounds:

A

high melting points and boiling points
good electrical conductivity when aqueous or
molten and poor when solid
good conductors of electricity in molten state or in a solution

41
Q

Explain in terms of structure and bonding the
properties of ionic compounds:

A

they have high melting/boiling points due to presence of strong electrostatic forces acting between oppositely charged ions =forces act in all directs and are very hard to overcome them

42
Q

The greater the charge of ions means…

A

the greater the electrostatic forces will be and the higher the mp and bp will be

43
Q

What is requires for electrical currents to flow?

A

freely moving charged particles such as ions or electrons present

44
Q

In what state do ionic compounds conduct electricity the best?

A

molten or in a solution as they have ions that can move and carry a charge

45
Q

When is a convalent bond formed?

A

when a pair of electrons is shared between two atoms leading
to noble gas electronic configurations

46
Q

What is the difference between ionic bonding and convalent bonding?

A

in covalent bonding the forces are quite weak whereas in ionic theyre the strongest type of chemical bond
metallic elements tend to form ionic bonds whilst non metallic elements tend to form covalent bonds
in ionic bonding it’s the attraction of eletrosatic forces of attraction of oppositely charged ions and in covalent the interaction of atoms are neutral and have no charge which makes them weaker

47
Q

Who can only participate in convalent bonding?

A

non metals

48
Q

When two or more atoms are contently bonded we describe them as…?

A

molecules

49
Q

How is a double bond formed

A

two adjacent atoms sharing a pair of electrons, two convalent bonds are formed=double bond formed

50
Q

How is a triple bond formed

A

two adjacent atoms sharing 3 pairs of electrons, three convalent bonds are formed=triple bond formed

51
Q

State the properties of simple molecular compounds

A

poor electrical conductivity
low melting points and boiling points due to weak intermolecular forces

52
Q

Describe diamond’s covalent structure?

A

each carbon atom bonds with 4 other carbons, forming a TETRAHEDRON
all covalent bonds are identical, very strong and there are no intermolecular forces

53
Q

Describe the giant covalent structures of graphite
and diamond

A

both substances contain only carbon atoms (due to the differences in bonding arrangements they are physically different)

54
Q

Describe the giant covalent structure of
silicon(IV) oxide, SiO2

A

it is a macromolecular compound which occurs NATURALLY as sand and quartz
oxygen atom forms covalent bond with 2 silicon atoms and each silicon atom in turn forms covalent bonds wit 4 oxygen atoms
has lots of very strong intermolecular forces
very hard
very high melting point
insoluble in water
doesn’t conduct electricity
cheap since it available naturally
used to make sand paper

55
Q

Describe the similarity in properties between
diamond and silicon(IV) oxide, related to their
structures

A

very high melting points due to regular repeating lattice and strong covalent bonds
don’t conduct electricity even when molten
strong

56
Q

What is diamond used for?

A

cutting tools

57
Q

What is graphite used for?

A

a lubricant and as an electrode

58
Q

What is metallic bonding?

A

e electrostatic attraction between the positive ions in a giant
metallic lattice and a ‘sea’ of delocalised
electrons

59
Q

Why do metals have good electrical conductivity, are malleable and ductile?

A

Because of strong metallic bonding
delocalization of electrons in metallic bonds confers to the electrical conductivity
layers of positive ions can slide over one another and take up different positions

60
Q

malleable definition

A

capable of being hammered out into a sheet

61
Q

ductile definition

A

capable of being drawn into a wire

62
Q

What is a giant covalent structure?

A

solids with very high melting points
all atoms are linked by strong covalent bonds which must be broken to melt the substance

63
Q

Describe the covalent structure of Graphite?

A

Each carbon atoms in graphite is bonded to three others forming layers of hexagons, leaving 1 free electron per carbon which becomes delocalized
covalent bonds within layers are very strong, but layers are attracted to each other by weak intermolecular forces

64
Q

properties of a diamond

A

doesn’t conduct electricity
very high melting point
it is extremly hard and dense
there are no freely moving charged particles to carry the current so it can’t conduct electricity
hard but brittle

65
Q

what is diamond used for?

A

jewlery for shiny appearance and for cutting tools since it is such hard material

66
Q

properties of graphite

A

conducts electricity
has a very high melting point
soft and slippery
less dense than diamond

67
Q

what is graphite used for?

A

pencils and industrial lubricant
lock
engines
used to make non-reactive elctrodes for electrolysis

68
Q

why do metals conduct electricity?

A

because of the free electrons available to move
electrons can flow= electricity is conducted

69
Q

Define an allatrope:

A

different structural forms of the same element in the same physical state

70
Q

what is an ionic bond

A

attraction of positive and negative ions

71
Q

why do ionic compounds have high melting points?

A

due to the large number of strong electrostatic attractions between the positive and neative ions

(due to strong ionoic bonding)

72
Q

what does covalent bonding consist of?

A

one or more shared pairs of electrons between two atoms

73
Q

what are delocalized electrons?

A

electrons that can move about between layers and are not bound to an individual atom

74
Q

what is a metallic bond?

A

electrostatic attraction between delocalised electrons and the positive metal ions in the lattice

75
Q

how can metals be so ductile and malleable

A

because of the layered structurz of the lattice - which cab slide over eachother without breaking the bonds

76
Q

how is the structure of macromolecular substances described as?

A

giant
macromolecular

77
Q

what does the molecular formula actually show?

A

actual number if atoms each ekement in a compound has

78
Q

what does the structural formulae show?

A

shows arrangement of atoms

79
Q

what is an alloy?

A

mixture containing a metal and another element (non metal or metal)

80
Q

what is an alloy?

A

mixture containing a metal and another element (non metal or metal)

Chemistry IGCSE (13 decks)

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