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Chemistry > C1 - The Periodic Table > Flashcards

C1 - The Periodic Table Flashcards

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1
Q

All substances are made of atoms. What is an atom?

A

An atom is the smallest part of an element that can exist

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2
Q

There are about ____ different elements

A

100

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3
Q

How are compounds formed?

A

Compounds are formed from elements by chemical reactions

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4
Q

State two features of chemical reactions

A

Always involve the formation of 1 or more new substances

Often involve a detectable energy change

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5
Q

What are compounds?

A

Compounds are two or more elements chemically combined in fixed proportions

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6
Q

What is a mixture?

A

A mixture consists of two or more elements or compounds NOT chemically combined together

The chemical properties of each substance in the mixture are unchanged

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7
Q

What physical processes can mixtures be separated by?

A

Filtration
Crystallisation
Simple distillation
Fractional distillation
Chromatography

Physical processes do not involve chemical reactions and no new substances are made!

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8
Q

Before the discovery of the electron, what were atoms thought to be?

A

Tiny spheres that could not be divided

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9
Q

What did the discovery of the electron lead to?

A

The plum pudding model of the atom. It suggested that the atom is a ball of positive charge with negative electrons embedded in it

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10
Q

What did the alpha scattering experiment conclude? / Why did the new evidence lead to a change in the atomic model?

A

Some alpha particles deflected right back, suggesting the Mass of an atom was concentrated at the centre (nucleus)

Some alpha particles deflected at angles, suggesting the nucleus must have positive charge

Most of the alpha particles passed through, suggesting atoms have empty space

This lead to the nuclear model. A key indication of how key experimental evidence can lead to a scientific model being changed or replaced

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11
Q

What did the alpha scattering experiment disprove?

A

The plum pudding model was replaced for the nuclear model

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12
Q

Describe the alpha scattering experiment

A

Alpha particles were fired at gold foil as it is thin

Some alpha particles passed through, others deflected and some bounced straight back off the gold foil

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13
Q

How did Niels Bohr adapt the nuclear model/add to it?

A

Suggested that electrons orbit the nucleus at specific distances.

The theoretical calculations of Bohr agreed with experimental observations

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14
Q

What did later experiments AFTER Niels Bohr lead to?

A

The idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles having the same amount of positive charge

These particles were called protons

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15
Q

About 20 years after the nucleus became an accepted scientific idea, what did the experimental work of James Chadwick provide evidence for?

A

The existence of neutrons within the nucleus

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16
Q

What is the relative charge of the particles in atoms?

A

Proton: +1
Neutron: 0
Electron: -1

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17
Q

Why do atoms have no overall electrical charge?

A

In an atom, the number of electrons is equal to the number of protons in the nucleus

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18
Q

The number of protons in an atom of an element is…

A

Its atomic number

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19
Q

Atoms are very small. What is their radius?

A

About 0.1nm (1 x 10^-10m)

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20
Q

What is the radius of a nucleus?

A

Less than 1/10,000 of that of the atom (1 x 10^-14m)

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21
Q

What are the relative masses of the particles in an atom?

A

Proton: 1
Neutron: 1
Electron: Very small

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22
Q

The sum of the protons and neutrons in an atom is…

A

Its mass number

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23
Q

What are isotopes?

A

Atoms of the same element that have the same number of protons but different number of neutrons

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24
Q

What is relative atomic mass (Ar)?

A

Average value that takes account of the abundance of the isotopes of the element

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25
Formula for Ar?
[(Mass no. of isotope 1 x % abundance of isotope) / (the latter for isotope 2)] x 100 Can include 3 isotopes!
26
How are elements in the periodic table arranged? Why? (3)
- In order of atomic (proton) number - Because Elements in the same group have the same number of electrons in their outer shell - Giving them similar chemical properties
27
Why is the periodic table named as it is?
Similar properties occur at regular intervals
28
Before the discovery of protons, neutrons and electrons, how did scientists classify elements?
By arranging them in order of their ATOMIC WEIGHTS
29
What was the issue with early periodic tables?
Were incomplete Some atoms were placed in inappropriate groups if the strict order of atomic weights were followed
30
What does the valence/outer electron of an atom represent?
Its group number
31
What does the amount of energy levels of an atom represent?
The row/period the element is in
32
How did Dimitri Mendeleev arrange the periodic table? (4)
Left gaps for undiscovered elements Predicted the properties of undiscovered elements Gaps were filled with newly discovered elements In some places, changed the order based on atomic weights
33
What explained why ordering elements on atomic weight was not always correct?
Isotopes
34
Elements that react to form positive ions are…
Metals on the left of the periodic table
35
Elements that do not form positive ions are…
Non-metals on the right of the periodic table
36
Where are metals and non-metals found on the periodic table?
Metals: Left, towards the bottom Non-metals: Right, towards the top
37
Compare metals and non-metals
Metals are strong and malleable, whereas non-metals are brittle Metals are good conductors of heat and electricity due to delocalised electrons, whereas non-metals do not generally conduct electricity Metals have a higher density, whereas non-metals have a lower density Metals have higher melting point and boiling points, whereas non-metals have lower MP and BPs Metals react to form positively charged ions, whereas non-metals react to form negatively charged ions
38
What are elements in group 0 called?
Noble gases
39
Why are noble gases inert (unreactive)?
They have full outer energy levels (except for Helium) and therefore have a stable arrangement. This means they do not need to gain or loose electrons
40
Explain why the boiling points of the noble gases increases going down the group (5)
- Boiling point increases - due to an increase in the number of electrons - creating a stronger negatively-charged force - leading to greater intermolecular forces - that require more energy to overcome
41
What are elements in group 1 called?
Alkali metals
42
Explain why reactivity increases going down group 1
Increasing reactivity because distance between outer shell and nucleus increases down the group So there is a weaker attraction between nucleus and outer shell So electron is more easily lost
43
Explain how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms
More outer shells = nucleus is further away from valence electrons so weaker attraction so electrons easily lost
44
Going down group 1, what happens to the MP and BP?
Both decrease
45
Compounds can only be separated into elements by _______ ________
Chemical reactions
46
What is filtration used for? This is all important to know if they give you a 6 mark mixture separation question
Separating insoluble solids from liquids
47
What is crystallisation used for?
Separating a soluble solid from a liquid
48
What is simple distillation used for?
Separating a liquid from a solid when we want to KEEP the solid
49
What is fractional distillation used for?
Separating liquids with different boiling points
50
What is chromatography used for?
To separate different dyes on ink
51
How do the FIRST 3 alkali metals react with oxygen, chlorine and water? (Malle sure you know how to compare them)
Water: vigorous reaction to form hydrogen gas and metal hydroxide Chlorine: vigorous reaction to form white metal chloride salt Oxygen: Combustion, vigorous reaction forming a metal oxide
52
What are three properties of alkali metals?
Soft Very reactive Low density
53
Describe group 7 elements
Non-metals Form 1- ion Diatomic elements
54
Explain why there is a higher melting and boiling point going down group 7
55
Explain why the reactivity of group 7 decreases going down the group
Distance between outer shell and the nucleus increases going down the group So weaker attraction between the nucleus and outer shell So harder to gain an electron
56
Define displacement in terms of halogens
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salts
57
Compare group 1 and the transition metals
Alkalis form +1 ions, whereas transition metals from ions of different charges Alkalis are soft, whereas transition metals are hard Alkali metals are low density, whereas transition metals are high density Alkali metals are not useful as catalysts, whereas transition metals are used as catalysts Alkali metals cannot from coloured compounds, whereas transition metals form coloured compounds Alkali metals have low melting points, whereas transition elements have high melting points Alkali metals are very reactive, whereas transition metals are less reactive
58
What are properties of the compounds Cr, Mn, Fe, Co, Ni and Cu
Chromium (CR) = uses to harden steel and resistant against corrosion Manganese (Mn) = Improves resistance to corrosion and used to make an alloy of aluminium for drink cans Iron (Fe) = Used to make steel and very resistant against corrosion and alloyed with carbon to make strong structures Cobalt (Co) = Hard and resistant to corrosion Nickel (Ni) = Hard, corrosion, resistant alloys Copper (Cu) = Unreactive so used for water pipes, malleable and conducts electricity
59
Suggest how to safely heat a substance and describe one way to ensure all salt is dissolved in water
Heat using a water bath/electric heater Heat/stir
60
Describe a method to separate a mixture of salt and sand
Place mixture in a beaker Add water to the mixture and stir using a glass rod Filter the mixture using a filter and funnel paper Dry the residue in a warm oven Evaporate some of the water from the filtrate using a water bath Leave the solution to cool for 24hrs to form crystals Remove and pat the crystals dry
61
Describe a method to carry out a simple chromatography experiment (6)
- Draw a line in pencil near the bottom of a piece of paper - Place a small sample of each ink on the pencil line - Pour a shallow layer of water into a beaker and place the paper in the beaker - The water should be below the paper line and ink spots - Place lid on the container and wait for solvent to rise to the top of the paper - Remove paper from the container
62
Describe how to separate chalk from potassium chloride
Add water to the mixture to dissolve potassium chloride Filter the mixture using a funnel and funnel paper The dissolved potassium chloride will pass through and the chalk residue will remain on top
63
Describe how a solution can be separated using simple distillation
The solution is boiled in rounded bottomed flask The solution with the lower boiling point evaporates first and passes through a condenser with cold water This condenses the gaseous solution into a liquid which is then collected in a beaker
64
Explain when to use fractional distillation instead of simple distillation
If boiling points are too close together, simple distillation cannot be used Fractional distillation allows substances with close boiling points to be separated As it provides a temperature gradient So only substances with a specific BP can reach the top to be separated off without condensing and running back into the flask
65
Describe a method for fractional distillation
66
Describe the nuclear model of the atom
A small positively charged nucleus surrounded by a cloud of negative electrons
67
Compare the plum pudding model and nuclear model of the atom
Both have area of positive charge Both have electrons Both are neutral overall The plum pudding model does not have a nucleus, whereas the nuclear model does The plum pudding model does not have protons or neutrons, whereas the nuclear model does The plum pudding model does not have shells/energy levels surrounding the nucleus, whereas nuclear model does The nuclear model has most of its mass concentrated in the nucleus, whereas the plum pudding model has the mass spread evenly Only plum pudding model has electrons arranged randomly in a ball of positive charge
68
What is the radius of the nucleus in relation to the radius of an atom?
Radius of a nucleus is 1/10,000 of the radius of an atom
69
Give 3 reasons why Mendeleev put iodine in the same group as chlorine
- Iodine has similar properties to other elements in group 7 - iodine has Similar reactivity to other elements in group 7 (Similar properties occur at regular intervals) - Iodine is a diatomic molecule
70
Explain why lithium and potassium are all in group 1 of the modern periodic table
- They have similar properties - They have similar reactivity as they have one electron in outer energy level/shell (Similar properties occur at regular intervals)
71
Describe the chemical and physical properties of group 1elements
Physical: soft, low density, low MP Chemical: very reactive, form 1+ ions and colourLESS compounds
72
Describe 4 things you would see when sodium is added to water
Fizzing Floats Moves on surface Melts/dissolves
73
State three observations that can be made during the reaction between magnesium and dilute hydrochloric acid
- Effervescence - Fizzing - Gets smaller and disappears
74
Explain why the reactivity of the elements increases going down group 1 from lithium to rubidium, yet decreases going down group 7 from fluorine to iodine
Distance between outer shell and nucleus increases down both groups So weaker attraction between nucleus and outer shell So easier for group 1 elements to lose an electron Harder for group 7 elements to gain an electron
75
Give two reasons why the discovery of gallium helped Mendeleev’s periodic table to become accepted (2)
- Correctly predicted the chemical properties of gallium - Gallium fit in a gap he left for future elements
76
Which group of elements had not been discovered when Mendeelev’s version of the periodic table was publicised?
Group 0 (noble gases)
77
Review diatomic molecules
78
What are the differences between compounds and mixtures?

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