Atomic structure

Question 1

What is the first event in the atomic timeline, who discovered it and when?

Answer 1

1803: Dalton: Solid atom model, all atoms of an element are identical; different elements have different atoms.

Question 2

What is the second event in the atomic timeline, who discovered it and when?

Answer 2

1897: Thomson: Discovers the electron.

Question 3

What is the third event in the atomic timeline, who discovered it and when?

Answer 3

1904: Thomson: Plum pudding model, atoms are spheres of positive charge with negative electrons dotted around inside.

Question 4

What is the fourth event in the atomic timeline, who discovered it and when?

Answer 4

1911: Rutherford: Solar system model, atoms have a positive nucleus surrounded by negative electrons in orbit.

Question 5

What is the fifth event in the atomic timeline, who discovered it and when?

Answer 5

1913: Bohr: Electron shell model, electrons occupy shells or energy levels around the nucleus.

Question 6

What is the sixth event in the atomic timeline, who discovered it and when?

Answer 6

1918: Rutherford: Discovers the proton.

Question 7

What is the seventh event in the atomic timeline, who discovered it and when?

Answer 7

1932: Chadwick: Discovers the neutron.

Question 8

A brief atomic timeline:

Answer 8

1803: Dalton: Solid atom model, all atoms of an element are identical; different elements have different atoms.
1897: Thomson: Discovers the electron.
1904: Thomson: Plum pudding model, atoms are spheres of positive charge with negative electrons dotted around inside.
1911: Rutherford: Solar system model, atoms have a positive nucleus surrounded by negative electrons in orbit.
1913: Bohr: Electron shell model, electrons occupy shells or energy levels around the nucleus.
1918: Rutherford: Discovers the proton.
1932: Chadwick: Discovers the neutron.

Question 9

Relative values:

Answer 9

Atoms are very small. Their diameters, masses and electrical charges are expressed as relative values.

Eg. The diameter of a hydrogen NUCLEUS is 1.75 x 10[-15]m. The diameter of a hydrogen ATOM is 1.06 x 10[-10]m.

The diameter of the nucleus relative to the atom=

1. 75 x 10[-15]
   - ————
2. 06 x 10[-10]

=1/60600

Question 10

What does an atom consist of?

Answer 10

A central nucleus, which:

• contains protons and neutrons
• is surrounded by electrons in shells

Question 11

How do you work out the number of neutrons?

Answer 11

Mass number - atomic number = neutrons

Question 12

What subatomic particle has a mass of almost 0?

Answer 12

electron

Question 13

What is the charge of a proton?

Answer 13

+1

Question 14

What is the charge of an electron?

Answer 14

-1

Question 15

Explain why atoms are electrically neutral overall.

Answer 15

Atoms contain equal numbers of protons and electrons.

Protons have a +1 charge and electrons have -1 charge (so charges cancel out).

Question 16

Describe the structure of an atom.

Answer 16

Central nucleus containing protons and (usually) neutrons.

Surrounded by electrons in shells.

Question 17

The mass of a proton is 1.6726 x 10[-27] kg.
The mass of an electron is 9.1094 x 10[-31] kg.
Calculate the mass of an electron relative to a proton.
Give your answer to 4 significant figures.

Answer 17

(9. 1094 x 10[-31])/(1.6726 x 10[-27]) =

5. 446 x 10[-4] or 1/1836

Question 18

What is the charge of a neutron?

Answer 18

0

Question 19

What is the mass of a proton?

Answer 19

1

Question 20

What is the mass of a neutron?

Answer 20

1

Question 21

What is the mass of an electron?

Answer 21

almost 0, 1/1836