Unit 3.1: Atom and Elements 1. Atoms are the smallest particle of an element 2. Atom consists of a nucleus and electron shell. 3. The nucleus is composed of protons and neutrons and the electrons orbit round the nucleus in different shells. 4. A model diagram for an atom is shown below: 5. Electron Shells: The electrons move round the nucleus in different energy levels. These energy levels are called electron shells. In first shell two electrons can stay. Second shell can hold up to eight electrons. Third shell can hold up to 8 electrons. 1 2 : Periodic Table.Unit 3. proton number. electron Substance particle Relative mass Relative charge Symbol Found in: Proton 1 +1 p Nucleus neutrons 1 0 n nucleus 1 Electron ≈0 -1 e Electron shells 1840 2 . 12 Element Nucleon number No of Proton No of electron No of Neutron Electronic arrangement 23 11Na 24 12Mg 16 8O 32 16S 39 19K 19 9F 9 4Be Unit 3. Mass number: The total number of protons and neutrons. Relative Atomic Mass (Ar) : Relative atomic mass is the weighted average mass of the isotope of the element. It 1 is measured by comparing with the mass of of carbon-12.3: isotopes and radioactivity 1. Isotopes : Isotopes are the atoms of the same element with different neutron number. 3. Atomic number : The number of protons in an atom. Isotopes are atoms of the same element with the same number of protons and electrons but different number of neutrons 2. 1. Examples: 1 2 3 1𝐻 1𝐻 1𝐻 12 13 14 6𝐶 6𝐶 6𝐶 3 . 2. 4. Thus an atom of Li (with three electrons) will have 2 electrons in the first shell. The third shell up to eight. 1 electron in the second shell.4: How electrons are arranged Arrangement of electrons 1. 5. The first shell can hold up to two electrons. 16 17 18 8𝑂 8𝑂 8𝑂 Element Proton number Nucleon number Number of neutron 1 1𝐻 2 1𝐻 3 1𝐻 12 6𝐶 13 6𝐶 14 6𝐶 16 8𝑂 17 8𝑂 18 8𝑂 Unit 3. We write this arrangement as 2.2 nucleus containing 12 protons and 12 neutrons +12 4 . 3. Electrons are arranged in shells.8. 2.2 24 12𝑀𝑔: 2.8.1 6. An atom of Mg (12 electrons) will be 2. The second shell up to eight 4. 8.1 19K 2.8. The elements far on the right of the table labelled Group 0 are inert gases (unreactive) have full outer shells. Group 1 3Li 2. e.8 etc).1 3.Uses of Electronic Configurations 1. Therefore elements in Group Valence electron Characteristics I II metals III IV V Non metals VI VII 0 Noble gas 4.1 11Na 2. 2. Member in the same group Will have the same number of valence electron.8.8. The chemical properties of elements Depend on the valence electrons.g.8. 5 . Ar is 2. octet or duplet (Ne is 2. X is placed in Group II of the periodic table Clone May/Jun 2013 The diagram shows an atom of an element +12 How many protons and neutrons are in the nucleus of the atom and in which group and period of the Periodic Table is the element found? Number of Number of Group number Period number protons neutrons A. 12 24 3 2 B.Test Power Clone May/Jun 2013 Element X is represented by 24 12𝑋 Which statement is represented by X is correct? A. 12 12 3 2 6 . X forms an ion by gaining electrons D. 12 12 2 3 C. 24 24 2 3 D. An atom of X contains 12 protons and 12 neutrons B. An atom of X contain 24 protons and 12 neutrons C. 7 . car frame. nails etc Copper is used in wire to conduct electricity Aluminium is used to make aluminium cans. Making use of metals Iron : used to make bridges. aircraft body etc 8 . Exceptions to those properties Some metals are soft : group 1 metals Some metal is liquid : mercury Hydrogen is non-metal gas located in group I Carbon is non-metal but graphite can conduct electricity while diamond has high melting and boiling point 3.5: The metals and non-metals 1.Unit 3. Differences between metal and non-metals Metals Non-metals Good heat and electrical conductor Do not conduct heat and electric High melting and boiling point Low melting and boiling point Hard and strong Hard but brittle Malleable and ductile Not malleable and not ductile Has shiny surface Has dull surface Produce ringing sound : sonorous Do not produce any sound when hit Have high density Have low density Form cations Form anions Produce basic oxides Produce acidic oxide 2. Making use of non-metals Air is made up of nitrogen. oxygen. carbon dioxide gases Water is made up of hydrogen and oxygen atoms Sand can be used to make glass Clay can be used to make ceramics Atomic structure 9 .4. 10 . 11 . 12 . 13 . Exercise The electronic structures of five atoms of different elements A. C. B. D and E are shown below 14 . Answer the following questions about these structures. In in Group V of the Periodic Table v. Each structure may be used once. Is in Period 4 of the Periodic Table ii. Has five electrons in its outer shell vi. Which structure i. Represents fluorine atom W 16/42 This question is about atoms. Is in Group II of the Periodic Table iv. Is a noble gas iii. more than once or not at all. Has a proton number of 7 viii. Represents calcium atom vii. ions and isotopes a) Define the term nucleon number [2] 15 . i.b) Give the electronic structure of the following atom and ion [2] Na P3 – c) State one medical use of radioactive isotopes [1] d) What is meant by the term relative atomic mass? [2] e) Suggest why the relative atomic mass of chlorine is not a whole number. neutrons and electrons. [2] f) Aluminium is a metal in Group III Describe the bonding in aluminium Include a labelled diagram and any appropriate charges in your answer [3] [Total 12] W16/432 a) Complete the table Particle Charge Relative mass Proton +1 Neutron 1 electron [2] b) The following are isotopes of carbon. how are these isotopes the same and how are they different? [3] They are the same because They are different because 16 . In terms of number of protons. [2] [total 9] W 16/41 – 3 The table gives some information about five substances 17 . Why do all isotopes of carbon have the same chemical properties? [1] c) Name two forms of the element carbon which have giant covalent structures [1] d) Complete the diagram to show the electron arrangement in a carbon dioxide molecule. Show the outer shell electrons only. ii.