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© KeMsoft20041 Menzies High School AS Chemistry © KeMsoft20042 AS Module 1 Atomic Structure Fundamental particles be able to describe the properties.

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Presentation on theme: "© KeMsoft20041 Menzies High School AS Chemistry © KeMsoft20042 AS Module 1 Atomic Structure Fundamental particles be able to describe the properties."— Presentation transcript:

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2 © KeMsoft20041 Menzies High School AS Chemistry

3 © KeMsoft20042 AS Module 1 Atomic Structure Fundamental particles be able to describe the properties of protons, neutrons and electrons in terms of relative charge and relative mass Protons, neutrons and electronsunderstand the importance of these particles in the structure of the atom Mass number and isotopes be able to recall the meaning of mass number (A) and atomic (proton) number (Z) be able to explain the existence of isotopes understand the principles of a simple mass spectrometer, limited to ionisation, acceleration, deflection and detection be able to interpret simple mass spectra of elements and calculate relative atomic mass from isotopic abundance, limited to mononuclear ions know that mass spectrometry can be used to determine relative molecular mass Electron arrangement be able to describe the electronic structures of atoms and ions up to Z = 36 in terms of levels s, p and d, considered as energy levels not quantum numbers understand how ionisation energies in Group II (Be - Ba) and in Period 3 (Na - Ar) give evidence for electron arrangement in levels and sub-levels

4 © KeMsoft20043 AS Module 1 Periodicity Classification of elements in s, p, and d blocks be able to classify an element as s, p or d block according to its position in the Periodic Table Properties of the elements of Period 3 (Na - Ar) to illustrate periodic trends be able to describe the trends in atomic radius, first ionisation energy, electronegativity, melting and boiling points of the elements Na - Ar understand the reasons for the trends in these properties Group II understand the trends in atomic radius, first ionisation energy, electronegativity and melting pouint of the elements Be - Ba know the reactions of the elements Be - Ba with water and recognise the trend know the relative solubilities of the hydroxides of the elements Be - Ba and that Mg(OH) 2 is sparingly soluble know the relative solubilities of the sulphates of the elements Be - Ba and that BaSO 4 is insoluble and is formed in the test for sulphate ions know that beryllium is atypical, limited to covalent character (e.g. in BeCl 2 ), the amphoteric character of Be(OH) 2 and the limitation of maximum co-ordination number to four

5 © KeMsoft20044 What is Ionisation M+M+ + M (g) The removal of an electron(s) from a gaesous atom to form an ion. The overall process is represented by an equation; (g) + e-e- MM+M+ + e-e

6 © KeMsoft20045 Ionisation Energy Since the energy involved in ionising a single atom is so small we define it for... 1 mol of electrons

7 © KeMsoft20046 I II III IV V VI VII O d Ionisation Energy - Trends s p S BCNOFNe AlSiPClAr LiBe Mg He Na H H: 1s 1 He:1s 2 Li: 1s 2 2s 1 Be: 1s 2 2s 2 B: 1s 2 2s 2 2p x 1 C: 1s 2 2s 2 2p x 1 2p y 1 N: 1s 2 2s 2 2p x 1 2p y 1 2p z 1 O: 1s 2 2s 2 2p x 2 2p y 1 2p z 1 F: 1s 2 2s 2 2p x 2 2p y 2 2p z 1 Ne: 1 s 2 2s 2 2p 6 Na: 1s 2 2s 2 2p 6 3s 1 Mg: 1s 2 2s 2 2p 6 3s 2 Al: 1s 2 2s 2 2p 6 3s 2 3p 1 Si: 1s 2 2s 2 2p 6 3s 2 3p x 1 3p y 1 P: 1s 2 2s 2 2p 6 3s 2 3p x 1 3p y 1 3p z 1 S: 1s 2 2s 2 2p 6 3s 2 3p x 2 3p y 1 3p z 1 Cl: 1s 2 2s 2 2p 6 3s 2 3p x 2 3p y 2 3p z 1 Ar: 1s 2 2s 2 2p 6 3s 2 3p 6

8 © KeMsoft20047 I II III IV V VI VII O Ionisation Energy - Trends s p S GaGeAsBrKr BCNOFNe AlSiPClAr SeKCa LiBe Mg He ScTiVCrMnFeCoNi Cu Zn Ba Sr Na H K: Ar4s 1 Ca: Ar4s 2 Sc: Ar4s 2 3d 1 Ti: Ar4s 2 3d 2 V: Ar4s 2 3d 3 Cr: Ar4s 1 3d 5 Mn: Ar4s 2 3d 6 Fe: Ar4s 2 3d 7 Co: Ar4s 2 3d 8 Ni: Ar4s 1 3d 10 Cu: Ar4s 1 3d 10 Zn: Ar4s 2 3d 10 Ga: Ar4s 2 3d 10 4p 1 Ge: Ar4s 2 3d 10 4p 2 As: Ar4s 2 3d 10 4p 3 Se : Ar4s 2 3d 10 4p 4 Br: Ar4s 2 3d 10 4p 5 Kr: Ar4s 2 3d 10 4p 6 d

9 © KeMsoft20048 I II III IV V VI VII O Ionisation Energy - Trends s p S GaGeAsBrKr FNe AlSiPClAr SeKCa LiBe Mg He ScTiVCrMnFeCoNi Cu Zn Ba Sr Na H d and in Period 3 (Na - Ar) understand how ionisation energies in Group II (Be - Ba) give evidence for electron arrangement in levels and sub-levels BCNO

10 © KeMsoft20049 Ionisation Energy - Trends c charge on the nucleus. Factors affecting the size of ionisation energy the attraction between the nucleus and the outer electron The greater will be the value of the 1 st I.E. d distance of the electron from the nucleus. n number of electrons between the outer electrons and the nucleus. The size of that attraction will be governed by: The more protons there are in the nucleus, the more positively charged the nucleus is, and the more strongly electrons are attracted to it. Attraction falls off very rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away. If there are filled shells of electrons between the outer electron and the nucleus they will cut off some of the attractive force of the nucleus – this known as screening or shielding. greater The greater 1s 2s 2p 3s 3p

11 © KeMsoft Ionisation Energy - Trends 1. Look up and tabulate the 1 st ionisation energies of the a) The Period 3 elements, b) The group II elements 2. Plot, by hand, graphs of the 1 st ionisation energies of... a)The Period 3 elements, b) The group II elements against their atomic numbers.

12 © KeMsoft Variation in 1 st Ionisation Energy with Proton Number Ionisation energy kJ/mol P3 Ionisation Energy - Trends Variation in 1 st Ionisation Energy with Proton Number Proton number Ionisation energy kJ/mol P3 Proton number

13 © KeMsoft Proton number 1 st Ionisation energy kJ/mol Variation in ionisation energy across Period 3 [Na Mg Al Si P S Cl Ar] Variation in 1 st Ionisation Energy with Proton Number Proton number Ionisation energy kJ/mol P3 General trend: As the proton number increases, the 1 st I.E. increases Successive increase in nuclear charge (+ve) means the outer electrons become more strongly held and need more energy to remove them. Ionisation Energy - Trends charge on the nucleus. The more protons there are in the nucleus, the more positively charged the nucleus is, and the more strongly electrons are attracted to it.

14 © KeMsoft Proton number 1 st Ionisation energy kJ/mol Variation in ionisation energy across Period 3 Variation in 1 st Ionisation Energy with Proton Number Proton number Ionisation energy kJ/mol P3 Ne3s 2 Ne3s 2 3p x 1 Two places where the general trend is not followed… p-orbital is higher in energy than an s orbital (further from the nucleus and screened) so the electron requires less energy to remove it; aluminium will have a lower 1 st I.E. than magnesium. Even though the nuclear charge has increased this is more than off-set by the greater energy and degree of shielding of the p-orbital electron. Ionisation Energy - Trends 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p 12p13p [Na /Li Mg/Be Al/B Si/C P/N S/O Cl/F Ar/Ne] Explain why boron has a lower first ionisation energy than beryllium. Bes outer electron in an s (2s) orbital (1) Bs outer electron is in a p (2p) orbital (1) 2p higher in energy than 2s – less energy needed to remove it(1) Explain why aluminium has a lower first ionisation energy than magnesium. Mgs outer electron in an s (3s) orbital (1) Als outer electron is in a p (3p) orbital (1) 3p higher in energy than 3s – less energy needed to remove it(1)

15 © KeMsoft Proton number 1 st Ionisation energy kJ/mol Variation in ionisation energy across Period 3 [Na /Li Mg/Be Al/B Si/C P/N S/O Cl/F Ar/Ne] Variation in 1 st Ionisation Energy with Proton Number Proton number Ionisation energy kJ/mol P3 Ne3s 2 3p x 1 p y 1 p z 1 Ne3s 2 3p x 2 p y 1 p z 1 In both cases the electron is removed from a p-orbital (same amount of shielding in both elements) but in phosphorus the electron lost is one of the unpaired p-electrons and in sulphur it is one of the paired electrons. The paired electrons repel each other and less energy is needed to remove one of them compared with the unpaired ones; sulphur therefore has a lower 1 st I.E. than phosphorus. Ionisation Energy - Trends 1s 2s 2p 3s 3p 16p Variation in ionisation energy across Period 3 Proton number P3 Two places where the general trend is not followed… 1s 2s 2p 3s 3p 15p electron lost in S is paired in a 3p orbital (1) electron lost in P is unpaired in a 3p orbital (1) repulsion between paired electrons (1) less energy needed to remove a paired electron than an unpaired one (1) Explain why sulphur has a lower first ionisation energy than phosphorus.

16 © KeMsoft Proton number 1 st Ionisation energy kJ/mol Variation in ionisation energy down Group II [Be Mg Ca Sr Ba] General trend: As the proton number increases, the 1 st I.E. decreases Successive increase in nuclear charge (+ve) does not make up for: the increased degree of shielding felt by the outer s-electron Its higher energy state Its greater distance from the nucleus So, the outer electrons become less strongly held and need less energy to remove them. Ionisation Energy - Trends 1s 2s 2p 3s 12p 1s 2s 2p 3s 20p 3p 4s 1s 2s 2p 3s 38p 3p 4s 3d 5s 3p s 2s 4p Be SrCaMg

17 © KeMsoft ELECTRON BEING REMOVED LOG 10 (IONISATION EERGY/kJmol) Ca: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Ca: 4s 2 3p 6 3s 2 2p 6 2s 2 1s 2

18 © KeMsoft ELECTRON BEING REMOVED LOG 10 (IONISATION EERGY/kJmol) Ca: 4s 2 3p 6 3s 2 2p 6 2s 2 1s 2

19 © KeMsoft200418


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