the model of the atom Flashcards

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1
Q

who developed the plum pudding theory and when?

A

JJ Thomson, 1897

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2
Q

what did John Dalton describe atoms as and when?

A

solid spheres, start of 18th century

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3
Q

what was the plum pudding model?

A

a model which showed the atom as a ball of positive charge with electrons stuck in it

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4
Q

what experiment did ernest rutherford conduct and when?

A

alpha scattering, 1909

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5
Q

what was the alpha scattering experiment?

A

they fired positively charged alpha particles at an extremely thin sheet of gold

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6
Q

what were the results of the alpha experiment expected to be?

A

expecting particles to pass straight through the sheet or be slightly deflected at most

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7
Q

why were the results predicted as they were?

A

the positive charge was thought to be spread out through the atom

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8
Q

what were the actual results of the alpha experiment?

A

most of the particles went straight through, some were deflected more than expected and some were deflected backwards

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9
Q

why did some particles pass straight through?

A

they passed through the empty space

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10
Q

why did some particles deflect?

A

they passed close to the nucleus

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11
Q

why did some particles deflect backwards?

A

they were fired at the nucleus

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12
Q

what was rutherford’s model called?

A

the nuclear model

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13
Q

what was the nuclear model?

A

there’s a positively charged nucleus at the centre where most of the mass is concentrated, a cloud of negative electrons surrounds the nucleus so most of the atom is empty space

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14
Q

who suggested electrons were in shells and when?

A

neils bohr, 1913

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15
Q

why was rutherford’s model proved wrong?

A

scientists realised electrons around the nucleus would be attracted to it, causing the atom to collapse

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16
Q

what did bohr propse?

A

electrons orbit the nucleus in fixed shells

17
Q

how long after the acceptance of nuclei were protons discovered?

A

20 years

18
Q

who carried out an experiment which provided evidence for protons and when?

A

james chadwick, 1932

19
Q

radius of an atom

A

1 × 10⁻¹⁰ m

20
Q

how can electrons move to a higher energy level?

A

by absorbing EM radiation

21
Q

how can electrons move to a lower energy level?

A

by emitting EM radiation

22
Q

isotopes

A

atoms with the same number of protons, but a different number of neutrons

23
Q

radioactive decay

A

when an unstable isotope gives out radiation to become a stable isotope