1.1 Inside the Atom
Sub-atomic particles
- Electrons revolve around in region of space called
- Electrons do not move in fixed
- The nucleus is made up of protons and neutrons which contains almost all the mass of the atom. This is because the mass of electrons is very small compared to
- The nucleus is positively-charged because of the Electrons, being negatively-charged, surround the nucleus.
Behaviour of sub-atomic particles in electric field
- Proton will be deflected towards the negative plate because it is positively-charged.
- Electron will be deflected towards the positive plate because it is negatively-charged.
- Neutron will not be deflected and continue in their direction of motion because it is neutral(not charged).
- Angle of deflection of electron > Angle of deflection of proton because the mass of electron is smaller than proton. (angle of deflection is inversely proportional to charge/mass ratio)
- Conclusion:
- Protons are positively-charged
- Electrons are negatively-charged
- Neutrons are neutral
- Protons are much heavier than electron
Nucleon number and proton number
- Proton number is the total number of protons in an
- Nucleon number is the total number of protons and neutrons in an
- Proton number is also known as atomic number while nucleon number is also known as mass
- In a neutral atom, the total number of protons equals to the total number of electrons.
- When an atom gains or loses electrons, a cation or anion will be
- Cation is a positively-charged It is formed when an atom loses electron(s). In cation, the number of protons is more than the number of electrons.
- Anion is a negatively-charged It is formed when an atom gains electron(s). In anion, the number of electrons is more than the number of protons.
- An atom or ion is said to be
- isoelectronic if they have the same number of
- isotonic if they have the same number of
- isotopic if they have the same number of
To deduce the number of protons, neutrons and electrons in an atom/ion
