Bonding (C2.2) | OCR GCSE Combined Science A (Gateway Science) — Chemistry — Foundation (J250)

Summary A simple electron energy level model can be used to explain the basic chemical properties of elements. When chemical reactions occur, they can be explained in terms of losing, gaining or sharing of electrons. The ability of an atom to lose, gain or share electrons depends on its atomic structure. Atoms that lose electrons will bond with atoms that gain electrons. Electrons will be transferred between the atoms to form a positive ion and a negative ion. These ions attract one another in what is known as an ionic bond. Atoms that share electrons can bond with other atoms that share electrons to form a molecule. Atoms in these molecules are held together by covalent bonds. Underlying knowledge and understanding Learners should be familiar with the simple (Dalton) atomic model. They should be familiar with the principles underlying the Mendeleev Periodic Table and the modern Periodic Table including periods and groups, and metals and non-metals. Learners should have some knowledge of the properties of metals and non- metals including the chemical properties of metal and non-metal oxides with respect to acidity.

Common misconceptions Learners do not always appreciate that the nucleus of an atom does not change when an electron is lost, gained or shared. They also find it difficult to predict the numbers of atoms that must bond in order to achieve a stable outer level of electrons. Learners think that chemical bonds are physical things made of matter. They also think that pairs of ions such as Na+ and Cl – are molecules. They do not have an awareness of the 3D nature of bonding and therefore the shape of molecules.

Reference	Mathematical learning outcomes	Maths skills
$CM2.2i$

estimate size and scale of atoms

represent three-dimensional shapes in two dimensions and vice versa when looking at chemical structures e.g. allotropes of carbon

translate information between diagrammatic and numerical forms

Learning outcomes	To include	Maths	Working scientifically	Practical suggestions
$C2.2a describe metals and non-metals and explain the differences between them on the basis of their characteristic physical and chemical properties$	$physical properties, formation of ions and common reactions e.g. with oxygen to form oxides$		$WS1.3f, WS1.4a$
$C2.2b explain how the atomic structure of metals and non-metals relates to their position in the Periodic Table$
$C2.2c explain how the position of an element in the Periodic Table is related to the arrangement of electrons in its atoms and hence to its atomic number$	$group number and period number$	$M1c$	$WS1.4a$
$C2.2d describe and compare the nature and arrangement of chemical bonds in: i. ionic compounds ii. simple molecules iii. giant covalent structures iv. polymers v. metals$		$M5b, M4a$	$WS1.4a$	$Make ball and stick models of molecules.$
$C2.2e explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons$			$WS1.4a$
$C2.2f construct dot and cross diagrams for simple covalent and binary ionic substances$		$M4a$	$WS1.4a$
$C2.2g describe the limitations of particular representations and models$	$dot and cross diagrams, ball and stick models and two- and three- dimensional representations$	$M5b$	$WS1.1c$
$C2.2h explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number$			$WS1.1b, WS1.3f, WS1.4a$
$C2.2i explain in terms of atomic number how Mendeleev’s arrangement was refined into the modern Periodic Table$			$WS1.1a, WS1.4a$

C2.2a describe metals and non-metals and explain the differences between them on the basis of their characteristic physical and chemical properties

physical properties, formation of ions and common reactions e.g. with oxygen to form oxides

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

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

group number and period number

C2.2d describe and compare the nature and arrangement of chemical bonds in: i. ionic compounds ii. simple molecules iii. giant covalent structures iv. polymers v. metals

Make ball and stick models of molecules.

C2.2e explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons

C2.2f construct dot and cross diagrams for simple covalent and binary ionic substances

C2.2g describe the limitations of particular representations and models

dot and cross diagrams, ball and stick models and two- and three- dimensional representations

C2.2h explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number

WS1.1b, WS1.3f, WS1.4a

C2.2i explain in terms of atomic number how Mendeleev’s arrangement was refined into the modern Periodic Table

Bonding

Next Steps

Learning Objectives