- Nucleus of an atom made of protons and neutrons. Electrons are negative, protons positive and neutrons neutral.
- Atomic number=number of protons Mass number=no. of protons+ no. of neutrons
- Atoms are neutral because they have equal number of electrons and protons
- Elements with same atomic no. but different mass no. are isotopes
- The different no. of neutrons in isotopes can be deduced
- The elements in the periodic table are arranged in the order of increasing atomic number; An electronic structure of 2.8.6 has 3 electron shells, so in in the 3rd row. The structure means the atomic number is 16
- Elements in the same group (same no. of electrons in outer shell) are arranged vertically and elemnts in the same period (order of how many shells the electrons occupy) are arranged horrizontally.
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