Atoms, elements and compounds

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Sample objectives

What this unit covers

• Elements, compounds and mixtures: Explain how elements, compounds, and mixtures differ from one another.
• Atomic structure and the Periodic Table: Explain that an atom consists of a central nucleus made up of neutrons and protons, with electrons orbiting in shells around it.
• Atomic structure and the Periodic Table: Identify the relative charges and masses of protons, neutrons, and electrons.
• Isotopes: Explain that isotopes are variations of the same element characterized by having identical proton counts but differing neutron counts.
• Isotopes: Understand and apply the symbols used to represent atoms and ions, such as C for carbon and Cl for chlorine, including their atomic numbers and mass numbers.
• Ions and ionic bonds: Explain how positive ions, called cations, and negative ions, known as anions, are formed.
• Ions and ionic bonds: Recognize that an ionic bond is a strong attraction between ions with opposite charges.
• Simple molecules and covalent bonds: Identify that a covalent bond occurs when two atoms share a pair of electrons, resulting in electronic configurations similar to noble gases.
• Simple molecules and covalent bonds: Explain how covalent bonds are formed in simple molecules such as H₂, CH₄, H₂O, I₂, NH₃, and CCl₄, using dot-and-cross diagrams to illustrate their electronic configurations.
• Giant covalent structures: Explain the giant covalent structures found in graphite and diamond.
• Giant covalent structures: Connect the structures and bonding of graphite and diamond to their applications, specifically: (a) graphite used as a lubricant and electrode (b) diamond utilized in cutting tools.
• Metallic bonding: Explain metallic bonding as the attraction between positively charged ions in a large metallic structure and the delocalised electrons surrounding them.
• Metallic bonding: Discuss how the structure and bonding of metals account for their properties, including (a) high electrical conductivity and (b) the ability to be shaped and stretched without breaking.