Note:

IGCSE Chemistry Notes on Atoms, Elements and Compounds

Objectives:

3.1 Atomic structure and the Periodic Table

Core 

• State the relative charges and approximate relative masses of protons, neutrons and electrons 
• Define proton number (atomic number) as the number of protons in the nucleus of an atom
• Define nucleon number (mass number) as the total number of protons and neutrons in the nucleus of an atom 
• Use proton number and the simple structure of atoms to explain the basis of the Periodic Table (see section 9), with special reference to the elements of proton number 1 to 20 
• Define isotopes as atoms of the same element which have the same proton number but a different nucleon number
• State the two types of isotopes as being radioactive and non-radioactive

Supplement 

• Understand that isotopes have the same properties because they have the same number of electrons in their outer shell

3.1 Atomic structure and the Periodic Table continued

Core

• State one medical and one industrial use of radioactive isotopes 
• Describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of the outer shell electrons. (The ideas of the distribution of electrons in s and p orbitals and in d-block elements are not required.) Note: A copy of the Periodic Table, as shown in the Appendix, will be available in Papers 1, 2, 3 and 4.

3.2 Structure and bonding

3.2.1 Bonding: the structure of matter

Core 

• Describe the differences between elements, mixtures and compounds, and between metals and non-metals 
• Describe an alloy, such as brass, as a mixture of a metal with other elements

3.2.2 Ions and ionic bonds

• Core 
• Describe the formation of ions by electron loss or gain 
• Describe the formation of ionic bonds between elements from Groups I and VII Supplement 
• Describe the formation of ionic bonds between metallic and non-metallic elements 
• Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions

3.2.3 Molecules and covalent bonds

Core

• Describe the formation of single covalent bonds in H2, Cl 2, H2O, CH4, NH3 and HCl as the sharing of pairs of electrons leading to the noble gas configuration 
• Describe the differences in volatility, solubility and electrical conductivity between ionic and covalent compounds Supplement
• Describe the electron arrangement in more complex covalent molecules such as N2, C2H4, CH3OH and CO2 
• Explain the differences in melting point and boiling point of ionic and covalent compounds in terms of attractive forces

3.2.4 Macromolecules

Core 

• Describe the giant covalent structures of graphite and diamond
• Relate their structures to their uses, e.g. graphite as a lubricant and a conductor, and diamond in cutting tools

Supplement 

• Describe the macromolecular structure of silicon(IV) oxide (silicon dioxide) 
• Describe the similarity in properties between diamond and silicon(IV) oxide, related to their structures

3.2.5 Metallic bonding

Supplement

• Describe metallic bonding as a lattice of positive ions in a ‘sea of electrons’ and use this to describe the electrical conductivity and malleability of metals