history of atoms

Question 1

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

Answer 1

Tiny spheres that couldn’t be divided

Question 2

What did the plum pudding model suggest

Answer 2

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

Question 3

What was concluded from alpha particle scattering experiment

Answer 3

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

Question 4

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

Answer 4

A particles went straight through gold foil

Question 5

What caused scientists to believe that the nucleus was positively charged

Answer 5

Some A particles were slightly deflected

Question 6

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

Answer 6

sometimes an alpha particle would bounce straight back

Question 7

What replaced the plum pudding model

Answer 7

The nuclear model

Question 8

What suggestion did Niels Bohr make?

Answer 8

Electrons orbit the nucleus at specific distances

Question 9

What did Rutherford realise?

Answer 9

Most of the atom is empty space

Question 10

Rutherford model

Answer 10

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

Question 11

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

Answer 11

discovery of the neutron

Question 12

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

Answer 12

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

Question 13

describe structure of nuclear model

Answer 13

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

Question 14

what did Bohr discover

Answer 14

electrons orbit the nucleus at specific distances

Question 15

how did Bohr’s theory modify the nuclear model

Answer 15

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

Question 16

difference between plum pudding model and nuclear model

Answer 16

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

Question 18

basic structure of an atom

Answer 18

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

Question 19

why does an atom have no overall charge?

Answer 19

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