Topic 1 Key Concepts in Chemistry - Structure of atom

Question 1

Describe the structure of an atom

Answer 1

Small central nucleus made up of protons and neutrons.
Electrons orbit (move around) the nucleus in shells.

Question 2

What is the radius of the nucleus? How large is it compared to the radius atom?

Answer 2

The radius of the nucleus is 1x10 to the power of -14m.

This is 1/10000 of the atomic radius.

Question 3

What are the relative masses of protons, neutrons and electrons?

Answer 3

Proton: 1
Neutron: 1
Electron: 1/1836 or 0.0005

Question 4

What are the relative charges of protons, neutrons and electrons?

Answer 4

Proton: +1
Neuton: 0
Electron: -1

Question 5

Why do atoms contain equal numbers of protons and electrons?

Answer 5

Atoms are stable with no overall charge.

Protons are positively charged and electrons negatively charged. For the charges to balance, the number of protons and electrons must be equal.

Question 6

Where is the mass of an atom concentrated?

Answer 6

In the nucleus.

Question 7

What does the atomic number of an atom represent?

Answer 7

The number of protons

Question 8

What does the mass number of an atom mean?

Answer 8

The mass number is the number of protons and neutrons found in the nucleus of an atom.

Question 9

Fill in the blank:

‘Atoms of the same element have the same number of ______ in the nucleus and this is unique to that element.

Answer 9

Protons

Question 10

What is an isotope?

Answer 10

Isotopes are atoms with the same number of protons (so they are the same element) but a different number of neutrons.

Isotopes of an element have the same atomic number but different mass numbers.