Topic 3 - Atomic Structure

Question 1

1.1 - Describe how Dalton’s model of the atom has changed over time

Answer 1

John Dalton’s theory was that all matter is made up of atoms. Atoms are indestructible small spheres that can’t be broken down. Atoms cannot be created or destroyed. Atoms in an element are identical.
However Thompson found that when a voltage is applied to a glass tube, rays were shown called cathode rays. When calculating the mass of these rays, he found that electrons in the rays were lighter than atoms, proving that atoms are made of smaller particles.

Question 2

1.2 - Describe the structure of an atom

Answer 2

There is a nucleus at the centre of an atom containing protons and neutrons, this is surrounded by electrons arranged as electron shells at different distances from the nucleus.

Question 3

1.3 - What is the relative charge and mass of subatomic particles?

Answer 3

Protons have a charge of 1+ and a mass of 1.
Electrons have a charge of 1- and a mass of 1/2000.
Neutrons have a charge of 0 and a mass of 1.

Question 4

1.4 - Explain why atoms contain equal number of protons and electrons

Answer 4

So that the charges cancel out and the atom has no overall charge.

Question 5

1.5 - Describe the difference in size between a nucleus and an atom

Answer 5

An atom is 100,000 times the diameter of a nuclei.

Question 6

1.6 - Where is the mass concentrated in an atom?

Answer 6

In the nucleus.

Question 7

1.7 - What is the mass number?

Answer 7

As the electrons mass is negligible, the sum of the protons and the neutrons in an atom is the mass number.

Question 8

1.8 - What does the atomic number tell about an element?

Answer 8

Atomic number is the number of protons, the number of protons are same in each atom of that element and is unique to it.

Question 9

1.9 - Define an isotope

Answer 9

Same number of protons but different number of neutrons in the nuclei.

Question 10

1.10 - Describe how to calculate subatomic particles given atomic number or mass number

Answer 10

Mass number is amount of nucleons.
Atomic number is amount of protons.
Nucleons - protons = neutrons
Amount of protons in an atom equals the electrons.

Question 11

1.11 - Why are some relative atomic masses not whole numbers?

Answer 11

Due to isotopes, there are different masses of an element as different number of neutrons leading to a number that isn’t an integer.

Question 12

1.12 - Describe how to calculate relative atomic masses

Answer 12

all of the isotopes (relative mass * abundance) / 100