Structure of the atom

• The three sub-atomic particles= protons, neutrons and electrons
• Nucleus= proton + neutrons
• The nucleus is big?


  No, is very much smaller than the atom but is the denser part
• Electrons= are arranged in shells around the nucleus
• Positive charge= protons
• neutral charge= neutrons
• negative charge= electrons
• In an atom the number of electrons and protons is always the same ?, so that means that the atom is neutral


  Yes, in an atom there are the same number of protons and electrons
• Atomic number (Z)= number of protons and electrons
• Mass number (A)= number of protons and neutrons
• What is an isotope?


  Are atoms of an element with the same number of protons and electrons, but different number of neutrons
• What is the relative atomic mass?


  Is a weighted average of the masses of the atoms of the isotopes
• What is an Ion?


  Atoms that lose or gain one or more electrons. They aren't neutral
• What is the energy shells?


  Are electrons arranged in different shells around the nucleus
• Which is the shell that is filled first?


  The innermost shell or lowest shell
• How many electrons we can put in the innermost shell?


  2 electrons
• How many electrons we can put in the 2 shell?


  8 electrons
• How many electrons we can put in the 3 shell?


  18 electrons