history of atoms Flashcards

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1
Q

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

A

Tiny spheres that couldn’t be divided

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2
Q

What did the plum pudding model suggest

A

That the atom was a ball of positive charge with negative electrons embedded in it.

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3
Q

What was concluded from alpha particle scattering experiment

A

Mass of an atom was concentrated at the centre
Nucleus was charged
Most of an atom is empty space

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4
Q

What caused scientists to believe that an atom was mostly empty space

A

A particles went straight through gold foil

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5
Q

What caused scientists to believe that the nucleus was positively charged

A

Some A particles were slightly deflected

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6
Q

What caused scientists to believe that the mass of an atom was concentrated in the nucleus

A

sometimes an alpha particle would bounce straight back

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7
Q

What replaced the plum pudding model

A

The nuclear model

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8
Q

What suggestion did Niels Bohr make?

A

Electrons orbit the nucleus at specific distances

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9
Q

What did Rutherford realise?

A

Most of the atom is empty space

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10
Q

Rutherford model

A

Positive nucleus in centre of an atom and negative electrons existing in a circle around nucleus

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11
Q

what did James Chadwick’s experimental work lead to 20 years after the nucleaus became an accpeted scientific idea

A

discovery of the neutron

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12
Q

Explain what led to the plum pudding model of the atom being replaced by the nuclear model of the atom. [6 marks]

A

most a particles went thru the foil meaning that an atom mostly consisted of empty space
sometimes A particles deflected at large angles so the concentration of mass is in the centre of an atom and nucleus is positively charged
plum pudding mass is spread throughoutthe atom
plum pudding charge is spread throughout the atom

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13
Q

describe structure of nuclear model

A

most of an atom is empty space with a postively charged nucleus in the centre with negitavely charged electrons on the edge

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14
Q

what did Bohr discover

A

electrons orbit the nucleus at specific distances

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15
Q

how did Bohr’s theory modify the nuclear model

A

electrons orbit the nucleus at specific distances rather than a general area called orbits which we know call energy levels or shells

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16
Q

difference between plum pudding model and nuclear model

A

in the P.P Model, negative electrons are scattered throughout the atom, where as in the nuclear model, negative electrons orbit the nucleus at a specific distance
In P.P.Model, the mass is evenly distributed where as in nuclear, the mass is concentrated in the centre of the atom
In P.P model, the atom is a ball of postive charge where as in nuclear, the centre of the atom (the nucleus) is postively charged

17
Q
A
18
Q

basic structure of an atom

A

positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons

19
Q

why does an atom have no overall charge?

A

there are the same amount of protons and electrons. electrons have a negative charge and protons have a positive charge so they both cancel eachother out. neutrons have no charge

20
Q
A