Topic 2.2 and 2.3 Atomic Structure and The Periodic Table and Isotopes -…
Topic 2.2 and 2.3 Atomic Structure and The Periodic Table and Isotopes
An atom is the smallest particle of an element that can exist
Atoms are made up of sub-atomic particles
The three sub atomic particles are protons, neutrons and electrons
The relative electric charge of a proton is positive, a neutron is neutral and a electron is negative.
The mass of electrons is negligible when the mass of the atom is calculated.
Protons and neutrons are found in the nucleus and mass of an atom is concentrated in the nucleus.
Atomic Number= Number of protons
Mass Number or Nucleon Number = No. of Protons + No. of Neutrons
Electrons are placed in electron shell
1st shell has a maximum of 2 electrons
2nd and 3rd shell have a maximum of 8 electrons.
Elements are arranged in horizontal rows called periods in order of increasing atomic number
number of occupied electron shells
is the same as the
that is written in numerical form
Elements with the same number of valence electrons are arranged in vertical columns called groups.
The number of valence electrons is the same as the group number.
Definition: Isotopes are atoms of the same element. That is, isotopes have the same number of protons but different mass number and number of neutrons.
Similarities between Isotopes
Same atomic number, number of protons
Same number of valence electrons hence same chemical properties.
Form compounds with the same formula.
Differences between Isotopes
Different mass number, number of neutrons
Different physical properties e.g. density and diffusion rate.