atomic model (basics)

Question 1

Describe the plum-pudding

model

Answer 1

The atom is a ball of positive charge with negative electrons embedded in it.

Question 2

Describe nuclear model and how it came

about

Answer 2

The nuclear model suggests that the atom has a small positively charged nucleus with negatively charged electrons lining the atom, but it’s mostly empty space

– it came about from the alpha scattering experiments

Question 3

What did the work of James Chadwick provide evidence for?

Answer 3

The existence of neutrons in the nucleus

Question 4

Describe the structure of an atom

Answer 4

The atom has a small central nucleus (made up of protons and neutrons)
around which there are electrons

Question 5

Explain why atoms are electrically neutral

Answer 5

They have the same number of electrons and protons, charges are cancelled.

Question 6

What is the radius of an atom?

Answer 6

0.1 nm (1x10^-10m)

Question 7

What is the radius of a nucleus and what is it compared to that of the atom?

Answer 7

1 x 10-14 m and 1/10000

Question 8

What name is given to the number of protons in the nucleus?

Answer 8

Atomic number

Question 9

Atoms of the same element have the same number of which particle in the nucleus?

Answer 9

Protons

Question 10

What was the alpha scattering experiment?

Answer 10

• Positively charged alpha particles were fired at a piece of thin gold
• most particles passed straight through the gold foil without changing direction, atoms mainly empty space
• some particles were deflected, changing directions as it passed through, centre of atom must have a positive charge
• some particles were deflected straight back, centre of atom must have mass (nucleus)
• lead to the development of the nuclear model

Question 11

What did Niels Bohr propose?

Answer 11

that electrons orbit the nucleus in specific distances rather than in a general area.