GCSE OCR Gateway Chemistry C2.2 a-c Metals and non-metals

New OCR Gateway specification from September 2016 Higher tier: grades 9 to 4: 

In this and subsequent posts I’m simply going to explain and illustrate each learning objective as they come up in the topics in the new GCSE specification. 

I’m giving you my notes from each lesson.

You can really get ahead of your class if you follow this blog and all the posts that will appear here about the new GCSEs over the coming months. 

This rejigging of the specification is just that: there is nothing really new here it has all been with us for the past half century at least.
 
And remember all that’s written in italics is for the higher tier paper only.

C2 Elements, Mixtures and Compounds

C2.2 Bonding

C2.2a describe metals and non-metals and explain the differences between them on the basis of their characteristic physical and chemical properties i.e. the formation of ions and common reactions, e.g. with oxygen to form oxides

Physical properties of metals and non-metals:

Metals:

Property            Explanation                                           Example

Sonorous           They clang when hit                             Brass

Hard                   No pressure leaves an impression       Osmium

Ductile               Can be stretched into thin wires          Gold

Malleable           Can be beaten in to flat sheets             Gold

Reflective           Can reflect light to form a mirror        Silver

Metals are also usually solid at rtp, silver coloured with high melting and boiling points.

Non-metals:

Non-metals tend to be soft e.g. sulphur, coloured e.g. red phosphorus and liquid e.g. bromine or gas e.g. noble gases at room temperature.

Metalloids:

These are elements between metals and non-metals in the Periodic Table.  They tend to have both metallic and non-metallic properties. 

Chemical properties

Formation of ions

Metals lose up to three electrons from their atoms to leave full outer shells and so form positive ions or cations.

Non-metals gain up to three electrons into their atoms to fill the outer shell and so form negatively charged ions or anions.

Non-metals also combine with other non-metals to form radical ions.  Radical ions can be positively or negatively charged.

Examples of radical ions are sulphate SO₄ ^2–, nitrate NO₃ ^–, and carbonate CO₃ ^2–

Metals and non-metals both combine chemically with oxygen to form oxides.

Metal oxides are generally basic and if soluble in water they are also alkaline.

1)     Magnesium

          2Mg   +     O₂     =     2MgO

Magnesium burns in oxygen with a very bright white flame.

Magnesium oxide is slightly soluble in water, the magnesium hydroxide solution formed is slightly alkaline about pH 8.

MgO   +      H₂O    =       Mg(OH)₂

2)     Copper

         2Cu    +   O₂        =       2CuO

Copper turns black when heated in air the black oxide coating on the metal is insoluble in water but dissolves in hot sulphuric acid to form blue copper sulphate solution.

CuO    +   H₂SO₄      =       CuSO₄      +     H₂O

Non-metal oxides tend to be soluble in water and generally form acidic solutions.

1)     Sulphur

         S       +       O₂      =       SO₂

Sulphur burns with a blue flame in air or oxygen produces dense fumes that are soluble in water and leave a solution of sulphurous (sulphur(IV)) acid pH2.

         SO₂   +       H₂O   =       H₂SO₃

2)     Carbon

         C       +       O₂      =       CO₂

Hot carbon powder ignites with orange sparks in pure oxygen the carbon dioxide forms dissolves in water to give a very weakly acidic solution pH6.

C2.2b explain how the atomic structure of metals and non-metals relates to their position in the periodic table

Metals are found on the left of the periodic table and non-metals on the right hand side as in the diagram below:

The reason is that metals tend to have three or less electrons in their outer shells whereas non-metals tend to have four or more electrons in their outer shells.

There are exceptions to this:

1) Hydrogen with one electron and helium with two electrons in its outer shell are both non-metals.

2) Going down a group of non-metals in the periodic table the elements become more metallic e.g. Group 4 (14) goes from carbon (C) to lead (Pb).

C2.2c explain how the position of an element in the periodic table is related to the arrangement of electrons in its atoms and hence to its atomic number

You can find the position of an element in the Periodic Table of the first 20 elements if you know its atomic number.

Let’s think about the element where atomic number Z=15.

Z=15 means 15 protons in the nucleus and 15 electrons in shells.

The first shell only contains two electrons, the second eight so the electron arrangement of Z=15 must be 2)8)5.

Therefore, with three shells the element is in Period 3 (Row 3).

With 5 electrons in its outer shell the element is in Group 5 (15).

So the element is Phosphorus P.

In the shortened Periodic Table below Hydrogen (H) is missing but the diagram is still useful, I think.

You can find a two minute explanation of how to build the electron structures from atomic numbers from Youtube here