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Flashcards in T1 - Key Concepts in Chemistry Deck (103):
1

Reactants

Molecules which react with each other

2

Products

Produced from the reactants

3

Symbol equations must be…

Balanced

4

What do state symbols tell you?

The state of substance in an equation

5

What are the 4 state symbols?

(s) - solid
(l) - liquid
(g) - gas
(aq) - aqueous (dissolved in water)

6

What is the chemical formula for ammonia?

NH3

7

When do ions form?

When atoms, or groups of atoms, gain or lose electrons to form charged particles

8

What’s the chemical formula for ammonium (include charge)?

NH4+

9

What’s the chemical formula for nitrate (include charge)?

NO3-

10

What’s the chemical formula for sulfate (include charge)?

SO4 2-

11

What’s the chemical formula for hydroxide (include charge)?

OH-

12

What’s the chemical formula for carbonate (include charge)?

CO3 2-

13

What can you write and ionic equation for and what do you need to do?

For any reaction involving ions that help in solution
Need to look at the balanced symbol equation and take out any aqueous ions that are present on both sides of the equation

14

Hazard

Anything that has the potential to cause harm or damage

15

Risk

The probability of someone or something being harmed if they are exposed to the hazard

16

What are the 6 hazards and what do they mean?

Oxidising – provides oxygen which allows other materials to burn more fiercely
Harmful - can cause irritation, reddening or blistering of the skin
Environmental hazard – harmful to organisms and to the environment
Highly flammable – catches fire easily
Toxic – can cause death by swallowing, breathing in, absorption through the skin…
Corrosive – destroys materials, including living tissue

17

Atoms

Tiny particles of matter which make up everything in the universe

18

What did John Dalton say about the atom?

At the start of the 19th century, he described atoms as solid spheres and said that different spheres made up the different elements

19

What did JJ Thompson say about the atom?

In 1897 he concluded from his experiments that they weren’t solids spheres. His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles (electrons)

20

What was the new theory that JJ Thompson came up with called?

‘plum pudding model’

21

Who proved that the plum pudding model was wrong and what experiment did they do?

Ernest Rutherford (1909) - Gold foil experiment (fired positively charged alpha particles at an extremely thin sheet of gold)

22

What did Rutherford expect to happen to the particles from the plum pudding model and what happened instead?

Expected – particles to pass straight through or be slightly deflected
Happened – most passed straight through, more than expected were deflected and a small number were deflected backwards

23

What is the name of Rutherford’s theory and what is it?

The nuclear atom – a tiny, positively charged nucleus at the centre, surrounded by a cloud of negative electrons (most of the atom’s empty space)

24

What was Niels Bohr’s theory?

Electrons contained in shells
Electrons can only exist in fixed orbits or shells and not anywhere in between
Each shell has a fixed energy

25

Subatomic particles

Protons, neutrons and electrons make up an atom

26

Relative mass

Measures mass on a scale where the mass of a proton neutron is 1

27

What are the relative charges of a proton, neutron and electron?

Proton - +1
Neutron - 0
Electron - -1

28

What are the relative masses of a proton, neutron and electron?

Proton - 1
Neutron - 1
Electron - 0.0005

29

About the nucleus

In the middle of the atom
Contains protons and neutrons
Positive charge
Almost all the mass is concentrated in it

30

About the electrons

Move around the nucleus and electrons shells
Negatively charged
Tiny but their shells cover a lot of space
Size of their shells depends on the size of the atom
Tiny mass

31

What is the radius of an atom?

About 10^-10m

32

What’s the overall charge of an atom?

Neutral

33

In an atom, the number of protons equals…

The number of electrons

34

What does the atomic number tell you?

How many protons and atom has

35

What does the mass number tell you?

The total number of protons and neutrons in the atom

36

How do you work out the number of neutrons in an atom?

Subtract the atomic number from the mass number

37

Isotopes

Different forms of the same element, which have the same number of protons but a different number of neutrons

38

Isotopes have the same… but different…

Same atomic number, different mass number

39

How many protons, electrons and neutrons does carbon – 12 and carbon – 13 have?

Carbon – 12:
Protons – 6
Electrons – 6
Neutrons – 6
Carbon – 13
Protons – 6
Electrons – 6
Neutrons – 7

40

On the periodic table, the elements have two numbers next to them. What number is the bigger one (top number)?

Relative atomic mass (Ar)

41

Relative atomic mass (Ar)

The average mass of one atom of the element, compare to 1/12 of the mass of one atom of carbon – 12

42

What’s the relative atomic mass chlorine and why?

35.5 because chlorine has two stable isotopes, chlorine – 35 and chlorine – 37, there is quite a lot of chlorine- 35 around and not so much chlorine – 37

43

Isotopic abundances

Different isotopes of an element occur in different quantities

44

How do you work out the relative atomic mass of an element?

Multiply each relative isotopic mass by its isotopic abundance, and add up the results. Divided by the sum of the abundances

45

Who made the first proper periodic table? And when?

Dmitri Mendeleev, in 1869

46

How did Mendeleev begin to sort the elements and after, what did he realise?

Began to sort the elements into groups based on their properties and the properties of their compounds. He realised if he put them in order of atomic mass, a pattern appeared (could put similar elements with similar chemical properties in columns)

47

Group (periodic table)

Ordered by how many electrons are in its outer shell

48

How many electrons do group 0 have on their outer shells?

Full outer shell - 8

49

Periods (periodic table)

The number of shells of electrons it has

50

What are the 3 electron shell rules?

Electrons always occupy shells (sometimes called energy levels)
Lowest energy levels are filled first
Only a certain number of electrons are allowed in each shell

51

How many electrons are sowed in the first, second and third shell?

First - 2
Second - 8
Third - 8

52

How are simple ions formed?

When atoms lose or gain electrons

53

Ion

Charged particles - can be single atoms or groups of atoms

54

Stable electronic structure

When atoms lose or gain electrons to form ions to get a full outer shell

55

Anions

Negative ions

56

Cations

Positive ions

57

Anions form when atoms....

Gain electrons (more electrons than protons)

58

Cations form when atoms....

Lose electrons (more protons than electrons)

59

What are the 4 groups that are most likely to form ions?

1,2,6 and 7

60

Group 1 and 2 elements are....
They... electrons to form.... ions

Metals, lose, positive

61

Group 6 and 7 elements are....
They... electrons to form.... ions

Non-metals, gain, negative

62

Ionic bonding

When a metal and a non-metal react together, the metal atom loses electrons to form a positive ion and the non-metal gains these electrons to form a negative ion.

63

Electrostatic forces

Force which holds oppositely charged ions which are strongly attracted to one another in ionic bonding

64

What diagram is used for ionic bonding?

Dot and cross diagram

65

What do dot and cross diagrams show?

The arrangement of electrons in an atom or ion. They show which atom the electrons in an ion originally came from

66

What is the structure of ionic compounds?

Giant ionic lattice structure

67

In ionic compounds, the ions form a closely packed regular lattice. What is the name of the force between oppositely charged ions in all directions?

Electrostatic forces of attraction

68

What is the name of the model which shows ionic compounds?

Ball and stick model

69

What are the 3 properties all ionic compounds have?

High melting and boiling points (because of the strong attraction between ions, takes a lot of energy to break)
Don’t conduct electricity as a solid but do when the ionic compound melts
They dissolve easily in water

70

Give 1 advantage and 1 disadvantage of 2D representations

Good at showing what atoms something contains and how they’re connected
Don’t show the shape or sizes of the substances

71

Give 1 advantage and 1 disadvantage about dot and cross diagrams

Show how compounds or molecules are formed and where the electrons in the bonds or irons come from
Don’t show the size or arrangement of atoms or ions

72

Give 1 advantage and 1 disadvantage of 3D models

Show the arrangement of irons
Only show the outer layer of the substance

73

Give 3 advantages and 3 disadvantages of ball and stick models

Show how the atoms in a substance are connected
Help to visualise structures
More realistic
Misleading
Don’t show the correct scales/sizes
Seems like there are big gaps where in reality there isn’t

74

Covalent bonding

Strong bond that forms when a pair of electrons is shared between two atoms

75

What diagram is used for covalent bonding?

Dot and cross diagram

76

Simple molecular substances

Substances made up of molecules containing a few atoms joined by covalent bonds

77

Describe the covalent bond in hydrogen

They have one electron so they need one more to complete the first shell. They can form a single covalent bond with another hydrogen atom to achieve this

78

Describe the covalent bond in hydrogen chloride

Both atoms only need one more electron to complete their outer shell

79

Describe the covalent bond in water

In water molecules and oxygen atom share a pair of electrons with two hydrogen atoms to form two single covalent bonds

80

Describe the covalent bond oxygen

An oxygen atom needs to more electrons to complete its outer shell. In oxygen gas each oxygen atom forms a double covalent bond (A bond made of two shared electron pairs) with another oxygen atom

81

Describe the covalent bond in methane

Carbon has four outer electrons, which is half its outer shell. It can form 4 covalent bonds with hydrogen atoms to fill up its outer shell

82

Describe the covalent bond in carbon dioxide

In carbon dioxide molecules, a carbon atom shares 2 pairs of electrons with two oxygen atoms to form 2 double covalent bonds

83

The atoms within the molecules bonded by covalent bonds are held together by…

Very strong covalent bonds

84

The forces of attraction between molecules formed by covalent bonds are…

Very weak

85

Why are the melting and boiling points of molecules bonded by covalent bonding low?

Because the molecules are easily parted from each other; only need to break the feeble intermolecular forces and not the covalent bonds

86

What state are most molecular substances at room temperature?

Gas or liquid

87

Do you molecular compounds formed by covalent bonding conduct electricity?

No because they don’t contain any free electrons or ions

88

Polymers

Molecules made up of long chains of covalently bonded carbon atoms

89

How are polymers formed?

When lots of small molecules called monomers join together

90

Name 4 properties that most giant covalent structures have

All the atoms are bonded to each other by strong covalent bonds
High melting and boiling points
Don’t contain charged particles – don’t conduct electricity (apart from graphite and graphene)
Aren’t soluble in water

91

Name 3 examples of carbon-based giant covalent structures

Diamond, graphite and graphene

92

Give 4 properties of diamond

Made up of a network of carbon atoms that each form 4 covalent bonds
High melting point – strong covalent bonds take lots of energy to break
Rigid lattice structure – really hard
Doesn’t conduct electricity

93

Give 4 properties of graphite

Each carbon atom only forms three covalent bonds creating sheets of carbon atoms arranged in hexagons
Aren’t any covalent bonds between the layers – weak so it’s soft and slippery
High melting point – covalent bonds need lots of energy to break
Conducts electricity - only three out of each carbon‘s 4 outer electrons are used in bonds so each carbon atom has one delocalised (free) electron

94

Give 3 properties of graphene

1 layer of graphite (fullerene)
Sheet of carbon atoms joined together in hexagons
Sheet is just 1 atom thick making it a 2D compound

95

Fullerenes

Molecules of carbon shaped like closed tubes or hollow balls

96

What are fullerenes used for?

Trap other molecules, the structure forms around another atom or molecule which is then trapped inside. This could be used to deliver a drug directly to the cells in the body

97

What structure do metals consist of?

Giant

98

What are the strong forces of electrostatic attraction between in metals?

Positive metal ions and the shared negative electrons

99

Metallic bonding

Forces of attraction hold the atoms together in a regular structure

100

Name 7 properties of metals

The electrostatic forces between metal ions and delocalised sea of electrons are strong
Shiny solids at room temperature
High melting and boiling points
Not soluble in water
More dense than non-metals
Malleable
Good conductors of electricity and heat

101

During a chemical reaction, no atoms are destroyed or created. However, why could the mass increase?

Because at least one of the reactants is a gas that’s found in the air and the products are solids, liquids or aqueous

102

During a chemical reaction, no atoms are destroyed or created. However, why could the mass decrease?

Because some, or all, of the reactants are solids, liquids or aqueous and at least one of the products is a gas

103

Relative formula mass (Mr)

The relative atomic masses of all the atoms in its formula added together