Protons, Neutrons & Electrons (CIE IGCSE Physics)

• The different particles that make up atoms have different properties
• Relative mass is a way of comparing particles. It is measured in atomic mass units (amu)
  • A relative mass of 1 is equal to mass of 1.67 × 10^-27 kg
• Charge can be positive or negative
  • Relative charge is, again, used to compare particles
• The fundamental charge is equal to the size of the charge on a proton and an electron, however the electron's charge is negative
• The properties of each of the particles are shown in the table below:

Table of Relative Charge & Mass

• If have a particle has 0 relative charge, this means it is neutral
• Both the proton and neutron relative mass is 1, this means that they have the same mass

• Nuclear charge is normally stated as the relative charge of the nucleus
  • The term 'relative' refers to the charge of the particle divided by the charge of the proton
• The proton number is the number of protons in a nucleus
• Since nuclei are made up of only protons and neutrons, the proton number determines the relative charge on a nucleus

Step 1: Determine the number of protons

• The number of protons is the proton number
• This is the bottom number in the AZX notation

 

• • This Chromium nucleus has 24 protons

Step 2: State the relative mass of 1 proton 

• 1 proton has a relative charge of +1

Step 3: Multiple relative charge of 1 proton by the number of protons

• This nucleus of Chromium therefore has a relative charge of +24

• Nuclear mass is stated as the relative mass of the nucleus
  • The term 'relative' refers to the mass of the particle divided by the mass of the proton
• The mass number is the total number of protons and neutrons in the nucleus
• The nucleon number (mass number) determines the relative mass of a nucleus

Step 1: Determine the number of protons and neutrons

• The number of protons and neutrons is the mass (nucleon) number
• This is the top number in the AZX notation

 

• • This Chromium nucleus has 52 protons and neutrons

Step 2: State the relative mass of 1 proton and neutron

• 1 proton has a relative mass of 1
• 1 neutron has a relative mass of 1

Step 3: Multiple relative charge of 1 proton and neutron by number of protons and neutrons

• This nucleus of Chromium therefore has a relative mass of 52