Chemistry: Atoms, Elements and Compounds
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Describe the difference between physical change and chemical change.
Chemical involves a change in the chemical structure of a substance but physical is a change in state.
Describe the differences between elements, compounds and mixtures.
Element is composed of a singular element, compounds are composed of multiple chemically bonded elements, and mixtures are not chemically bonded.
Describe the structure of an atom in terms of electrons and a nucleus containing protons and neutrons.
An atom is made of a nucleus comprised of protons and neutrons, and an equal amount of electrons to protons orbiting the nucleus in shells to give a neutral charge.
Describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of valency electrons (the ideas of the distribution of electrons in s and p orbitals and in d block elements are not required).
Electron configuration: Shells are layers which can only hold a certain amount of electrons in each layer. These are accordingly placed in periods to show how many layers an atom of an element has. e.g. Carbon. 2, 6
State the relative charges and approximate relative masses of protons, neutrons and electrons.
Protons - positive charge, relative mass of 1. Neutrons - no charge, relative mass of 1. Electrons - negative charge, relative mass of negligible.
Define atomic (proton) number and mass (nucleon) number.
Atomic number - Amount of protons. Mass number - Amount of neutrons + protons. Atomic number = Mass number - protons.
Use proton number and the simple structure of atoms to explain the basis of the Periodic Table (see section C9), with special reference to the elements with proton numbers 1 to 20. (A copy of the Periodic Table will be provided in Papers 1 and 3.)
Period - number of shells. Group - number of electrons in valence shell.
Describe the formation of ions by electron loss or gain.
Particles are not stable without a full valence shell, and so will swap with other atoms to form ions, and become ionically bonded, losing or gaining electrons. Metals tend to lose electrons, and non-metals gain.
Describe the formation of ionic bonds between elements from Groups I and VII.
Group 1 element loses an electron, Group 7 element gains the one the Group 1 element donated. Thus they become ionically bonded.
Explain the formation of ionic bonds between metallic and non-metallic elements.
Metals tend to lose electrons to become stable, and these electrons are donated to non-metals, and thus form an ionic bond. Both ions are stable.
State that non-metallic elements form nonionic compounds using a different type of bonding called covalent bonding involving shared pairs of electrons.
Non-metallic elements can bond by sharing electrons, known as covalent bonding. These bonds are stronger than ionic bonds.