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Science Chemistry > C1 and C2 > Flashcards

C1 and C2 Flashcards

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1
Q

what is an element?

A

a substance with only one type of atom

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2
Q

what is a compound?

A

a substance with more than one type of atom

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3
Q

what do all atoms contain?

A

-a tiny nucleus at its centre surrounded by electrons

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4
Q

what is a mixture?

A

-made up of two or more substances that are not chemically combined together

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5
Q

how can mixtures be separated?

A
  • filtration
  • crystallisation
  • simple distillation
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6
Q

how was the first person to put forward ideas about atoms?

A

-It was not until the early 1800s when John Dalton put forward his ideas about atoms

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7
Q

What were Dalton’s ideas about atoms?

A
  • Elements only contain one type of atom
  • Atoms get re-arranged in chemical reactions
  • Atoms are solid spheres that cannon be split into simpler particles
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8
Q

Who discovered the electron?

A

-J.J. Thompson discovered the electron at the end of the 1800s

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9
Q

Who discovered the plum pudding model?

A

-J.J. Thompson

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10
Q

What were Thompson’ ideas about atoms? (plum pudding model)

A
  • Tiny negatively charged electrons must be embedded in a cloud of positive charge
  • He imagined the electrons as bits of plum in a plum pudding
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11
Q

What was Rutherford’s ideas about the atom?

A
  • The positive charge of an atom must be concentrated at a tiny spot in the centre of the atom (nucleus)
  • Electrons must be orbiting around the nucleus which contains very dense positively charged protons
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12
Q

Which sub-atomic particle did J.J. Thompson discover?

A

-Electrons

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13
Q

Explain the rutherford gold foil experiment?

A
  • Geiger and Marsden did experiment with radioactive particles between 1908 + 1913
  • They fired a beam of dense, positively charged particles (alpha particles) at very thin gold foil
  • They expected particles to pass straight through gold atoms
  • But some alpha particles emerged from the foil at different angles and some came straight back
  • Scientists realised that the alpha particles were being repelled + deflected by a tiny concentration of positive charge in the atom
  • the plum pudding model was replaced with the nuclear model of an atom
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14
Q

What was Niels Bohr’s ideas about an atom?

A
  • Electrons must be orbiting the nuclues at set distances

- Electrons much be orbiting the nucleus in certain fixed energy levels (shells)

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15
Q

Why did Bohr revise Rutherford’s model of the atom?

A

-He noticed that the light given out when atoms were heated only had specific amounts of energy

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16
Q

When was Bohr’s model of the atom discovered?

A

-In 1914

17
Q

How were neutrons discovered?

A
  • In 1932 James Chadwick did an experiment that could only be explained by the existance of neutrons
  • Because neutrons have no charge, it was very difficult to detect them in experiments
18
Q

What are atoms made up of?

A
  • Protons
  • Neutrons
  • Electrons
19
Q

What is the relative charge of a proton, electron and a neutron?

A
  • Protons have a relative charge of +1
  • Electrons have a relative charge of -1
  • Neutrons have no electric charge. They are neutral
20
Q

What is the relative mass of a proton, electron and a neutron?

A
  • Protons have a relative mass of 1
  • Neutrons have a relative mass of 1
  • Electrons have a relative mass of 0
21
Q

Why do all atoms carry no overall charge?

A

-Because atoms contain an equal number of protons and electrons

22
Q

What is the atomic number?

A

-Number of protons (so number of electrons)

23
Q

What is the mass number?

A

-Number of protons and neutrons

24
Q

How do you calculate the number of neutrons?

A

Number of neutrons = mass number - atomic number

25
Q

what is an ion?

A

-An atom that has gained or lost electrons forming negative or positive ions

26
Q

What do atoms that gain electrons form?

A

-Negative ions

27
Q

What do atoms that lose electrons form?

A

-Positive ions

28
Q

What are isotopes?

A
  • Atoms of the same element with different numbers of neutrons
  • They have identical chemical properties, but their physical properties, such as density, can differ
29
Q

how many electrons can be fitted on each shell?

A
  • the first shell holds up to 2 electrons
  • the second shell holds up to 8 electrons
  • the third shell holds up to 8 electrons
  • the fourth shell holds up to 18 electrons
  • 2,8,8,18
30
Q

what does the outermost shell determine?

A

-the number of electrons on the outermost shell determines the way in which that element reacts

31
Q

Who created the periodic table?

A

Dmitri Mendeleev

32
Q

How did Mandellev proof his periodic table?

A

-He left gaps for the unknown elements, which when discovered matched his predictions

33
Q

What are group 1 and 2 in the periodic table?

A
  • Reactive metals: these metals react vigorously with outher elements, and most react with water
  • These metals are all soft
34
Q

Transition elements and their properties:

A
  • These metals are usually very reactive
  • Some like silver and gold are very unreactive
  • Have high melting and boiling points
  • Are hard and tough
  • Have high densities
  • Good conductors of heat and electricity
35
Q

Noble gases and their properties:

A
  • low boiling points
  • non-metal elements
  • very unreactive
  • Density increases you go down
  • Colourless
36
Q

Group 1 - the alkali metals and their properties:

A
  • Very reactive (stored in oil to stop reacting with oxygen in the air)
  • Reactivity increases as you go down
  • Low density
  • Very soft
  • Silvery/shiny surface when first cut
  • Surface quickly goes dull as metals react with oxygen in the air. This form a layer of oxide on surface
  • They form 1+ ions in reactions to make ionic compounds
  • low melting + boiling temperatures for metals
  • melting + boiling points decrease as you go down
  • React with water to produce hydrogen and an alkaline solution containing the metal hydroxide
37
Q

What does electronic structure affect?

A

The properties of difference groups on the periodic table

38
Q

Group 7 - the halogens and their properties:

A
  • The halogens form ions with a single negative charge in their ionic compounds with metals
  • Toxic non-metals
  • Low melting and boiling points
  • Melting and boiling points increase as you go down
  • Poor conductors of heat and electricity
  • They form covalent compounds by sharing electrons with other non-metals
  • Elements get less reactive as you go down
  • A more reactive halogen can displace a less reactive halogen from a solution of one of its salts

Science Chemistry (5 decks)

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