Metals & Non-Metals (AQA GCSE Combined Science: Synergy: Physical Sciences): Revision Note

Location of metals and non-metals

Where are metals and non-metals?

• Elements can be divided into two broad types: metals and non-metals

  • Metals are found on the left and towards the bottom of the periodic table

  • Non-metals are found on the right and towards the top of the periodic table

• Most elements are metals

Trends across the periodic table

• Metallic character decreases moving from left to right across a period

  • Going across a period, the overall positive charge inside the nucleus increases

  • This means that the electrons are more strongly attracted

  • This causes them to be harder to lose

• Metallic character increases moving down a group

  • Going down a group, the outer electrons are further from the nucleus

  • This means that the electrons are less strongly attracted

  • This causes them to be easier to lose

Properties of metals and non-metals

Ion formation

• An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons

  • This loss or gain of electrons takes place to obtain a full outer shell of electrons

• An element's atomic number determines the number of electrons in its atoms and how those electrons are arranged in shells

  • This electron arrangement determines how the element reacts and what ions it forms.

Metal ions

• Elements that react by losing their outer electrons form positive ions

  • Metals form positive ions

• Metals only have a few outer electrons

  • This makes them easy to remove

• Group 1 metals want to lose one outer electron

  • They become a 1+ ion, e.g. Li⁺

• Group 2 metals want to lose two outer electrons

  • They become a 2+ ion, e.g. Mg²⁺

• Going down a group, outer electrons are further from the nucleus and held less strongly

  • This is why reactivity increases down groups like Group 1

Non-metal ions

• Elements that react by gaining electrons form negative ions

  • Non-metals form negative ions

  • (Hydrogen is an exception as it can form positive or negative ions)

• A non-metal's outer shell of electrons is almost full

  • It is easier to gain a small number of electrons than to lose many electrons

• Group 6 non-metals want to gain two electrons

  • They become a 2- ion, e.g. O^2-

• Group 7 non-metals want to gain one electron

  • They become a 1- ion, e.g. Cl^-

• Going down a group, there are more electron shells

  • This means that there is less attraction from the nucleus towards an incoming electron

  • This is why reactivity decreases down groups like Group 7

• This is a key difference between metals and non-metals and influences their chemical behaviour