LJH
Chapter 1 Atoms, Molecules and Stoichiometry
1.1Structure of the atom
Fundamental particles in an atom: proton, neutron, electron
Particle Mass/kg Relative mass Relative charge
Proton, p 1.67x 10-27 1 +1
Electron, e 9.11x 10-31 1/1839 -1
Neutron, n 1.67x 10-27 1 0
The mass of an atom is very small. Thus, mass of an atom is expressed in atomic mass unit
(amu).
1 a.m.u. = x mass of one atom of 12C = 1.66x 10-27kg
All atoms of an element have the same proton number.
Proton number of an element is the number of protons in one atom of the element.
Nucleon number of an atom is the sum of the protons and neutrons in the atom.
*There is no such term as “electron number” or “neutron number”, both must be described
as “number of electrons” and “number of neutrons”.
, LJH
- Effect of an electric field on subatomic particles.
The direction flow of proton is the direction of current while electrons are opposite.
OR
The positive proton deflects towards negative plate whereas negative electrons deflect
towards positive plate.
The neutron which is neutral do not deflect to any plate.
-Effect of a magnetic field on subatomic particles
For magnetic field, deflection of the subatomic particles determined by Fleming’s Left Hand
Rule.
General rule:
The angle of deflection usually depends on the mass/charge (m/e) ratio.
The larger the m/e value, the smaller the angle of deflection.
The electron deflects more than proton due to the lighter mass.
, LJH
Ions:
When a chemical reaction take place, only the valence electrons are involved, while the
number of protons and neutrons in an atom unchanged.
Types of ions: Cation and Anion
Cation: Ions with positively charged. The number of protons is more than number of
electrons.
Cation is formed by losing electrons and become a positive ion.
Usually only metal elements can form cation.
Eg:
Ion Na+ Mg2+ Al3+
Number of protons 11 12 13
Number of electrons 10 10 10
Anions: Ions with negative charges. The number of electrons is more than the number of
protons.
Anion is formed by receiving electrons and become a negative ion.
Usually only non-metal elements can form anion.
Eg:
Ion N3- O2- F-
Number of protons 7 8 9
Number of electrons 10 10 10
Isoelectronic species: Species with the same number of electrons. For example, all the ions
from the table above.
Chapter 1 Atoms, Molecules and Stoichiometry
1.1Structure of the atom
Fundamental particles in an atom: proton, neutron, electron
Particle Mass/kg Relative mass Relative charge
Proton, p 1.67x 10-27 1 +1
Electron, e 9.11x 10-31 1/1839 -1
Neutron, n 1.67x 10-27 1 0
The mass of an atom is very small. Thus, mass of an atom is expressed in atomic mass unit
(amu).
1 a.m.u. = x mass of one atom of 12C = 1.66x 10-27kg
All atoms of an element have the same proton number.
Proton number of an element is the number of protons in one atom of the element.
Nucleon number of an atom is the sum of the protons and neutrons in the atom.
*There is no such term as “electron number” or “neutron number”, both must be described
as “number of electrons” and “number of neutrons”.
, LJH
- Effect of an electric field on subatomic particles.
The direction flow of proton is the direction of current while electrons are opposite.
OR
The positive proton deflects towards negative plate whereas negative electrons deflect
towards positive plate.
The neutron which is neutral do not deflect to any plate.
-Effect of a magnetic field on subatomic particles
For magnetic field, deflection of the subatomic particles determined by Fleming’s Left Hand
Rule.
General rule:
The angle of deflection usually depends on the mass/charge (m/e) ratio.
The larger the m/e value, the smaller the angle of deflection.
The electron deflects more than proton due to the lighter mass.
, LJH
Ions:
When a chemical reaction take place, only the valence electrons are involved, while the
number of protons and neutrons in an atom unchanged.
Types of ions: Cation and Anion
Cation: Ions with positively charged. The number of protons is more than number of
electrons.
Cation is formed by losing electrons and become a positive ion.
Usually only metal elements can form cation.
Eg:
Ion Na+ Mg2+ Al3+
Number of protons 11 12 13
Number of electrons 10 10 10
Anions: Ions with negative charges. The number of electrons is more than the number of
protons.
Anion is formed by receiving electrons and become a negative ion.
Usually only non-metal elements can form anion.
Eg:
Ion N3- O2- F-
Number of protons 7 8 9
Number of electrons 10 10 10
Isoelectronic species: Species with the same number of electrons. For example, all the ions
from the table above.
