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Chemistry IGCSE > Atoms, elements and compounds > Flashcards

Atoms, elements and compounds Flashcards

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
maximum capacity of electrons the first shell can hold
2
26
maximum capacity of electrons the second shell can hold
8
27
maximum capacity of electrons the third shell can hold
8
28
Define the term isotope
different atoms of the same element that have the same number of protons but different numbers of neutrons
29
What is an ion?
ELECTRICALLY CHARGED atom or group of atoms formed by the loss or gains of electrons
30
Do isotopes of the same element have the same chemical properties?
isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration
31
Where does the loss or gain of electrons take place in?
outer most shell
32
Explain the ionisation of metals or formation of cations
all metals can loose electrons to other atoms to become positive ions known as CATIONS
33
Explain the ionisation of non-metals or formation of cations
all non metals can gain electrons from other atoms to become negatively charged ions, known as ANIONS
34
State what an ionic bond is
a strong electrostatic attraction between oppositely charged ions that keep ionic compounds together
35
How are ionic compounds formed? Explain
when metals react with non-metals Metals loose one of their outermost electrons and non-metals GAIN to form positive and negative ions
36
What are positive and negative ions hold together by?
electrostatic forces of attractions between opposite charges
37
Describe the giant lattice structure of ionic compounds
regular arrangement of alternating positive and negative ions
38
How is the lattice structure of ionic compounds?
GIANT, has regular arrangement of alternating positive and negative ions
39
What is formed when when metal atoms and non-metal atoms react?
Ionic compounds
40
Describe the properties of ionic compounds:
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
Explain in terms of structure and bonding the properties of ionic compounds:
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
The greater the charge of ions means...
the greater the electrostatic forces will be and the higher the mp and bp will be
43
What is requires for electrical currents to flow?
freely moving charged particles such as ions or electrons present
44
In what state do ionic compounds conduct electricity the best?
molten or in a solution as they have ions that can move and carry a charge
45
When is a convalent bond formed?
when a pair of electrons is shared between two atoms leading to noble gas electronic configurations
46
What is the difference between ionic bonding and convalent bonding?
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
Who can only participate in convalent bonding?
non metals
48
When two or more atoms are contently bonded we describe them as...?
molecules
49
How is a double bond formed
two adjacent atoms sharing a pair of electrons, two convalent bonds are formed=double bond formed
50
How is a triple bond formed
two adjacent atoms sharing 3 pairs of electrons, three convalent bonds are formed=triple bond formed
51
State the properties of simple molecular compounds
poor electrical conductivity low melting points and boiling points due to weak intermolecular forces
52
Describe diamond's covalent structure?
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
Describe the giant covalent structures of graphite and diamond
both substances contain only carbon atoms (due to the differences in bonding arrangements they are physically different)
54
Describe the giant covalent structure of silicon(IV) oxide, SiO2
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
Describe the similarity in properties between diamond and silicon(IV) oxide, related to their structures
very high melting points due to regular repeating lattice and strong covalent bonds don't conduct electricity even when molten strong
56
What is diamond used for?
cutting tools
57
What is graphite used for?
a lubricant and as an electrode
58
What is metallic bonding?
e electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons
59
Why do metals have good electrical conductivity, are malleable and ductile?
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
malleable definition
capable of being hammered out into a sheet
61
ductile definition
capable of being drawn into a wire
62
What is a giant covalent structure?
solids with very high melting points all atoms are linked by strong covalent bonds which must be broken to melt the substance
63
Describe the covalent structure of Graphite?
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
properties of a diamond
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
what is diamond used for?
jewlery for shiny appearance and for cutting tools since it is such hard material
66
properties of graphite
conducts electricity has a very high melting point soft and slippery less dense than diamond
67
what is graphite used for?
pencils and industrial lubricant lock engines used to make non-reactive elctrodes for electrolysis
68
why do metals conduct electricity?
because of the free electrons available to move electrons can flow= electricity is conducted
69
Define an allatrope:
different structural forms of the same element in the same physical state
70
what is an ionic bond
attraction of positive and negative ions
71
why do ionic compounds have high melting points?
due to the large number of strong electrostatic attractions between the positive and neative ions (due to strong ionoic bonding)
72
what does covalent bonding consist of?
one or more shared pairs of electrons between two atoms
73
what are delocalized electrons?
electrons that can move about between layers and are not bound to an individual atom
74
what is a metallic bond?
electrostatic attraction between delocalised electrons and the positive metal ions in the lattice
75
how can metals be so ductile and malleable
because of the layered structurz of the lattice - which cab slide over eachother without breaking the bonds
76
how is the structure of macromolecular substances described as?
giant macromolecular
77
what does the molecular formula actually show?
actual number if atoms each ekement in a compound has
78
what does the structural formulae show?
shows arrangement of atoms
79
what is an alloy?
mixture containing a metal and another element (non metal or metal)
80
what is an alloy?
mixture containing a metal and another element (non metal or metal)

Chemistry IGCSE (13 decks)

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