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IGCSE Chemistry > [C3] Atoms, elements and compounds > Flashcards

[C3] Atoms, elements and compounds Flashcards

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1
Q

Define an isotope

A

atoms of the same element which have the same proton number but a different nucleon number

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2
Q

Define nucleon number

A

(mass number) as the total number of protons and neutrons in the nucleus of an atom

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3
Q

Define proton number

A

(atomic number) as the number of protons in the nucleus of an atom

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4
Q

Define the term solvent

A

It is the substance in which the solute is dissolved

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5
Q

Define the term solute

A

a solid that is dissolved in a solvent

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6
Q

Define the term solution

A

The mixture formed when a solute dissolves in a solvent

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7
Q

Define the term concentration

A

the amount of a substance in a defined space.

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8
Q

Name the 3 elements in an atom

A

Central nucleus (containing protons, neutrons)
Shells of electrons

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9
Q

Define an element

A

A substance that cannot be further broken down by any chemical reaction.
(Each element has a unique number of protons in its atom)

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10
Q

Define mixture

A

A mixture is made from different substances that are not chemically joined.

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11
Q

Define compound

A

A compound is formed when two or more atoms join together chemically, with covalent or ionic bonds

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12
Q

Describe the difference between a mixture and a compound {2}

A
  • Mixture is made from different substances but not chemically joined together. They can be separated by physical methods.
    -Compound is made from different substances when they are chemically joined together
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13
Q

Describe 4 differences between metals and non-metals [4]
(7 are listed on the other side)

A

Metals- Shiny, high melting points, good conductors of electricity and heat, high density, malleable

Non-metals- Dull, low melting points, poor conductors of electricity and heat, low density, Brittle

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14
Q

Describe the lattice structure of ionic compounds

A

A regular arrangement of alternating positive
and negative ions,
ex. the sodium chloride structure

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15
Q

How do you identify physical changes from chemical changes?

A

Physical changes are to do with the state of matter. The substance will be a different shape or size at the end but no new substances are formed.

Chemical changes produce a new substance and either absorbs or releases energy during the reaction. Chemical reactions are on a nuclear level

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16
Q

Give 2 examples of physical changes [2]

A

boiling water, melting ice, breaking a bottle, crumbling paper.

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17
Q

Give 2 examples of chemical changes [2]

A

burning wood, dissolving salt in water, and digesting food.

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18
Q

State the different forms of carbon [2]

A

Diamond, graphite

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19
Q

Describe the giant covalent structure of diamond

A

Every carbon atom is bonded to 4 other carbon atoms with strong covalent bonds

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20
Q

Describe the giant covalent structure of graphite

A

Each carbon is bonded by 3 strong covalent bonds to make a giant structure consisting of layers of hexagons

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21
Q

State the relative mass and charge for
- protons [2]
-neutrons [2]
-electrons [2]

A

Protons- mass= 1 charge= +1
neutrons- mass=1 charge= 0
electrons- 1/12000 charge= -1

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22
Q

State 2 uses for radioactive isotopes

A
  • Used in medicine (sterilise equipment or treat cancer tumours)
  • Used in industry (to detect leaks in pipes)
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23
Q

Why do isotopes have the same chemical properties?

A

Because they have the same number of electrons in their outer shells

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24
Q

Describe the formation of an anion
(state which atoms become anions)

A

If an atom gains electrons, there are more electrons than protons so, negative ions are formed
(Non-metals gain electrons to become anions)

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25
Q

What is the name of a negatively charged ion?

A

Anion

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26
Q

What is the name of a positively charged ion?

A

Cation

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27
Q

Describe the formation of a cation
(State which atoms become cations)

A

If an atom loses electrons, there are more protons than electrons, so a positive ion is formed
(Metals lose electrons to become cations)

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28
Q

Describe a noble gas outer shell

A

It is full (this is called the noble gas electronic structure)

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29
Q

When atoms react they achieve this stable _______ by losing or gaining electrons to form ions.

A

A. Noble Gas electronic structure

30
Q

What is noble gas electronic structure?

A

When the outer shell of the atom is full

31
Q

How are the elements arranged in the periodic table?

A

In proton number order

32
Q

What are the columns in the periodic table?

A

Groups- elements with similar properties are grouped together

33
Q

What does the Group Number tell you?

A

How many electrons are in the outer shell
ex. Group 1- Li, Na, K, all have 1 electron in their outer shell

34
Q

Which group contains elements with full outer shells?

A

Group 8 (VIII)

35
Q

What are the rows called?

A

Periods
(in period 1 Shell 1 is being filled, in period 2 Shell 2 etc…)

36
Q

What is an ionic bond and how is it formed? [2]

A

Formed by the transfer of electrons.
The oppositely charged ions are held together by a strong electrostatic attraction, this is called an ionic bond. It is a bond between metallic and non-metallic elements

37
Q

Define an ionic bond

A

An ionic bond is the strong electrostatic attraction between oppositely charged ions.

38
Q

Define a covalent bond

A

A single covalent bond is a shared pair of electrons between 2 atoms

39
Q

State how covalent bonds are formed

A

When non-metal elements react, their atoms join together with covalent bonds (a pair of electrons is shared)

40
Q

Describe the differences in
Volatility, solubility, electrical conductivity
between ionic and covalent compounds

A

Volatility:
Ionic- low volatility
Covalent- high volatility
Solubility:
ionic- often not soluble in water
Covalent- mostly insoluble in water
Electrical conductivity:
ionic- does not conduct electricity solid, conduct when molten
Covalent- does not conduct electricity

41
Q

Which has stronger forces of attraction between atoms and why?

A

A. Ionic compounds because of the strong force between the opposite charges

42
Q

State the difference in melting point and boiling point between ionic and covalent compounds (in terms of attractive forces)

A

Melting point:
Ionic- High melting point due to strong forces of attraction
Covalent- Low melting point due to weak forces of attraction
Boiling point:
Ionic- High boiling point due to strong forces of attraction
Covalent- Low boiling point due to weak forces of attraction

43
Q

Explain why graphite can conduct electricity when diamond cant [2]

A

Diamond has no delocalised electrons
Graphite conducts electricity because the fourth electron of every carbon atom is unbonded and moves among the layers in a sea of delocalised electrons

44
Q

State some 3 properties of diamond

A
  • Hardest natural substance
  • Has a very high melting point
  • Does not conduct electricity
45
Q

Why is graphite used as a lubricant?

A

Because the layers are not bonded together with covalent bonds just a weak force of attraction so the layers can slide over each other, making graphite a good lubricant

46
Q

Describe a use for diamond

A

Cutting tools or drill bits

47
Q

Describe 2 uses for graphite

A

a lubricant or a conductor

48
Q

Describe the macromolecular structure of silicon (IV) oxide

A

Similar structure to a diamond except instead of carbon, there are alternating silicon and oxygen atoms. It also has similar properties to diamond e.g hard, and high melting point

49
Q

Which of the following would be a physical changes?
a) Acid base neutralisation
b) Metal displacement
c) Boiling ethanol
d) Combustion of magnesium

A

C
Because:
- When ethanol boils it changes from liquid to gas

50
Q

Which of the following statements best describes activation energy?

a) The minimum energy released when colliding particles react
b) The minimum energy required for particles to react
c) The maximum energy required for particles to react
d) The maximum energy released when colliding particles react

A

B

51
Q

Non-metallic elements form simple molecules with _______ _______ between atoms.

A

covalent bonds

52
Q

What does a period (row) tell you about all the elements in that period?

A

How many electrons in a shell

53
Q

Why are the noble gases very unreactive?

A

They have a full outer shell = most stable configuration

54
Q

How are ions formed?

A

Positive ions - when they lose an electron
negative ion - when they gain an electron

55
Q

What types of elements are iconic bonds formed between?

A

Metal and non-metal

56
Q

Describe the structure of an ionic compound

A
  • Big lattice structure
  • Held together by electrostatic attraction
  • Alternating between positive and negative ions
57
Q

Why do atoms form covalent bonds ?

A

To obtain a more stable structure (full outer shell)

58
Q

Give an example of a compound that contains at least 1 covalent bond

A

H², Cl², H²O, CH⁴, NH³ & HCL

59
Q

Compare the volatility of ionic and covalent compounds [3]

A
  • Ionic compounds have low volatility
  • Giant covalent compounds have low volatility
  • compounds have high volatility
60
Q

Compare the solubility of ionic and covalent compounds

A

Iconic - Generally soluble
Covalent - Insoluble in water

61
Q

What are the uses of graphite and why

A

Electrode because they conduct electricity and have hight boiling points
Lubricant because it’s slippery

62
Q

Describe the structure of graphite

A

In graphite, each carbon is covalently bonded to 3 other carbons, forming layers
of hexagonal rings, which have no covalent bonds between the layers.

63
Q

Describe the formation of ionic bonds between elements from Groups 1 and 7

A

when ionic bonds are formed between group 1 and 7:
- group 1 atom loses one electron and forms a +1 ion
- group 7 atom gains the electron the group 1 atom lost and becomes a -1
ion

64
Q

Describe the formation of ionic bonds between metallic and
non-metallic elements

A

Metal + Non-metal: electrons in the outer shell of the metal atom are transferred
- Metal atoms lose electrons to become positively charged ions
- Non-metal atoms gain electrons to become negatively charged ions

65
Q

Why do isotopes have the same properties?

A
  • they have the same number of electrons in their outer shell
  • electrons in the outer
    shell is responsible for chemical reactions
66
Q

First shell can have up to
___ electrons
Second shell can have up to ___ electrons
Third shell can have up to ___ electrons

A

2
8
8

67
Q

Which change to an atom occurs when it forms a positive ion?

A )It gains electrons.
B ) It gains protons.
C )It loses electrons.
D It loses protons.

A

C

68
Q

“Electrons from each element are shared by both of the elements in a compound.”
Which compound matches this description?

A ) lead bromide
B ) sodium chloride
C ) water
D ) zinc oxide

A

C

69
Q

Which statement about bonding is not correct?

A ) Carbon can form four single covalent bonds.

B) Chlorine atoms react to gain a noble gas electronic structure.

C) Covalent bonding involves losing and gaining electrons.

D) Hydrogen molecules have the formula H2.

A

C

70
Q

Why are small covalent molecules liquids or gases at room temperature?

A
  • When small molecules melt or boil, it’s the weak intermolecular forces that break.
  • Since these intermolecular forces are weak and break easily, simple covalent molecules have very low melting and boiling points.
  • Therefore, they exist as liquid and gases at room temperature.
71
Q

Why do ionic compounds have a low electrical conductivity when not in a solution but a high electrical conductivity when dissolved in a solution?

A
  • When not in a solution the ions are not free to move so cannot create a current.
  • When they get dissolved in a solution, the ions can move around and so can create a current very easily.

IGCSE Chemistry (14 decks)

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