Atomic Structure And The Periodic Table Flashcards

1
Q

What are all substances made of?

A

Atoms (smallest part of an element that can exist)

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2
Q

What is an element?

A

A substance that contains only one sort of atom.

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3
Q

How are compounds formed?

A

From elements by chemical reactions, chemical reactions always involve a detectable energy change.

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4
Q

What do compounds always contain?

A

Two or more elements chemically combined in fixed proportions and can be represented by formulae by using the symbols of the atoms from which they are formed.

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5
Q

How can compounds be separated into elements?

A

By chemical reactions

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6
Q

Total mass of products=

A

Total mass of reactants, no atoms lost/made

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7
Q

What is does mixture consist of?

A

Two or more elements not chemically combined. The chemical properties of each substance in the mixture are unchanged.

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8
Q

How can mixtures be separated?

A

Using physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.

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9
Q

What is filtration?

A

Used to separate soluble solids from insoluble solids.

E.g. a mixture of salt (soluble) and sand (insoluble) can be separated by dissolving salt in water then filtering the mixture.

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10
Q

What is crystallisation?

A

Used to obtain a soluble solid from a solution

E.g. salt crystals can be obtained from a solution of salty water.

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11
Q

How can salt crystals can be obtained from a solution of salty water?

A

1) Gently warm the mixture

2) Water evaporates leaving crystals of pure salt

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12
Q

What is simple distillation?

A

Used to obtain solvent from solution

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13
Q

What is fractional distillation?

A

Used to separate mixtures in which the components have different boiling points.

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14
Q

What is chromatography?

A

Used to separate the different soluble, coloured components of a mixture e.g. the different colours added to a fizzy drink.

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15
Q

What can new experimental evidence cause a scientific model to be?

A

Changed/replaced

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16
Q

What were atoms thought to be before the discovery of the electron?

A

Tiny spheres that could not be divided.

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17
Q

What did the discovery of the electron lead to?

A

The plum pudding model of the atom.

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18
Q

What did the plum pudding model suggest?

A

The atom is a ball of positive change with negative electrons embedded in it.

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19
Q

Which experiment was carried out in 1909?

A

The alpha particle scattering experiment where scientists fired alpha particles at a sheet of extremely thin gold foil.

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20
Q

What did the scientists expect to happen to the alpha particles in the experiment?

A

For them to pass straight through the foil or to be slightly deflected because the positive charge of each atom was thought to be spread out through the ‘pudding’ of the atom.

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21
Q

What actually happened to the alpha particles in the scattering experiment?

A

Most of them went straight through, some were deflected more than expected and some were deflected straight back.

22
Q

Which model explained the out come of the scattering experiment?

A

The nuclear model.

23
Q

What did the nuclear model explain?

A
  • There’s a cloud of negative electrons surrounding the nucleus so most of it’s empty space.
  • There’s a tiny positively charged nucleus, where most of the mass is concentrated.
24
Q

What happened when alpha particles came near the concentrated, positive charge of the nucleus?

A

They are deflected- if they were fired directly at the nucleus, they were deflected backwards. Otherwise, they passed through the empty space.

25
Q

How did Neil Bohr adapt the nuclear model?

A

He suggested that electrons orbit the nucleus at different distances, Bohr’s theoretical calculations agreed.

26
Q

Which idea did experiments after Neil Bohr’s discovery lead to?

A

The idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. These were protons.

27
Q

What evidence did James Chadwick’s work provide evidence for?

A

The existence of neutrons within the nucleus about 20 years after the nucleus became a scientific idea.

28
Q

What is the relative atomic mass of an element?

A

An average value that takes account of the abundance of the isotopes of the element.

29
Q

What are isotopes?

A

An element that has the same number of protons but a different number of neutrons.

30
Q

What is the electron configuration for the first 20 elements?

A

2,8,8,18

31
Q

How are elements arranged in the periodic table?

A

In order of atomic number so that elements with similar properties are in columns known as groups. Elements in the same group in the PY have the same number of electrons in their outer shell giving them similar chemical properties.

32
Q

Why is the periodic table called the periodic table?

A

Similar properties occur at regular intervals.

33
Q

How did scientists classify elements before the discovery of protons, neutrons and electrons?

A

In order of atomic weights

34
Q

What was the problem with ordering elements in atomic weights?

A

The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of the atomic weights was followed.

35
Q

How did Mendeleev overcome the problems of the original periodic table?

A

He left gaps for elements that he thought had not yet been discovered and in some places changed the order based in atomic weights.

36
Q

What helped to explain why the order based on atomic weights was not always correct?

A

Knowledge of isotopes

37
Q

Which elements react to form positive ions?

A

Metals

38
Q

Which element for negative ions?

A

Non-metal

39
Q

What are the majority of elements?

A

Metals.

40
Q

Where are metals and non-metals found on the periodic table?

A

Metals- found to the bottom of periodic table

Non-metals- To the right and top of the periodic table

41
Q

What are group 0 known as?

A

The noble gases.

42
Q

What are some overall properties of the noble gases?

A

They are unreactive and do not form molecules easily because their atoms have stable arrangements of electrons. Their boiling points increase as you go down the group.

43
Q

How many electrons do noble gases have in their outer shell?

A

8 apart from helium which has 2

44
Q

What do the increasing boiling points of noble gases mean?

A

There are greater intermolecular forces between them as you go down the group which need to be overcome.

45
Q

What are the noble gases?

A
Helium 
Neon
Argon
Krypton
Xenon
Radon
46
Q

What are the elements in group 1 known as?

A

Alkali metals

47
Q

Why are alkali metals stored in oil?

A

They react very vigorously with oxygen and water (including the moisture in the air).

48
Q

What are group 7 metals known as?

A

Halogens - they have 7 electrons in their outer shell

49
Q

What are the properties of transition metals?

A
  • High melting points
  • Strong
  • Not very reactive
  • Useful as catalysts
  • Form coloured compounds
  • High density
  • React with water forming an alkaline solution
  • Can form different ions
50
Q

How do alkali metals compare with transition metals?

A

Properties of alkali metals:

  • Relatively low melting point
  • Very reactive
  • Form white compounds
  • Soft & white can be cut with a knife
  • Low density, some float on water
  • Form 1+ ions
  • React with water forming hydrogen gas
51
Q

What are the properties shared by alkali and transition metals?

A
  • Form ionic compounds one reaction with non-metals

- Good thermal and electrical conductors