2.3 ATOMIC STRUCTURE

• What is meant by the proton number?

  The number of proton in a nucleus of an atom
• What does nucleon number mean?

  The total number of protons and neutrons in the nucleus of an atom.
• Nucleon number = number of protons + number of neutrons
• Nucleon number = proton number + number of neutrons
• The sodium atom has a proton number of 11 and the chlorine atom has a proton number of 17. This shows that..

  Atoms of different elements have different proton numbers.
• Are there any elements with the same number of protons?

  No. Only isotopes of the same element can have same number of protons.
• How to know if an atom is neutral?

  When the number of electrons is the same with the number of protons.
• When is an anion(negatively-charged ion) formed?

  When the number of electrons increases.
• When is a cation(positively-charged ion) formed?

  When the number of electrons decreases.
• The picture shows the standard representation of an atom. State what is A,Z and X.

  A is the nucleon number

  Z is the proton number

  X is the symbol of an element