periodic table

• period number


  the number of electron shells of an atom
• elements in the same group have the same number of valence electrons
• the elements are arranged according to increasing proton number from left to right
• vertical column in periodic table


  group
• horizontal row in periodic table


  period
• elements in the same group have similar chemical properties such as forming
• charge of group 1

  1+
• charge of group 16


  2-
• down a group, metals become more metallic (more reactive) because the atom size becomes bigger as there are more electron shells, the valence electrons is/are further away from the nucleus, so the attraction force for the electrons becomes weaker, the metal thus can lose the valence electrons more easily.
• Trends across a period:

  elements - changed from metals to non-metals (left to right)
• Trends across a period:

  oxides - changed from basic to amphoteric to neutral to acidic
• Trends across a period:

  elements - changed from strong reducing agent to strong oxidising agent
• Trends across a period:

  The atom size becomes smaller (from Group 1 to 17) as the number of protons increases but the number of electron shells remain the same, the attraction force of the positively charged nucleus increases, hence exerting a stronger hold on the electrons, thus shrinking the distance between the shells and the nucleus.
• Diatomic

  2 atoms covalently bonded
• charge: number, +/-