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© Boardworks Ltd 2003 KS4: ATOMS
© Boardworks Ltd 2003 A slide contains teacher’s notes wherever this icon is displayed - To access these notes go to ‘Notes Page View’ (PowerPoint 97) or ‘Normal View’ (PowerPoint 2000). Normal ViewNotes Page View Teacher’s Notes Flash Files A flash file has been embedded into the PowerPoint slide wherever this icon is displayed – These files are not editable.
© Boardworks Ltd 2003 Atoms – the building blocks All substances are made from very tiny particles called atoms. John Dalton had ideas about the existence of atoms about 200 years ago but only recently have special microscopes been invented that can “see” them. Water
© Boardworks Ltd 2003 Elements – different types of atom Elements are the simplest substances. There are about 100 different elements. Two of John Daltons ideas were: –Elements contain different types of atom. –Each element has only one type of atom. N S O C Fe K
© Boardworks Ltd 2003 Atoms – How Small? small.Atoms are about 1/100,000,000 cm across. They are small. To make an atom the size of a football we would have to magnify it to around 3,000,000,000 times its normal size If we magnified the size of a football by the same amount it would stretch from the UK to the USA! N X 3,000,000,000
© Boardworks Ltd 2003 Atoms – How Heavy? A single grain of sand contains billions of atoms of silicon and oxygen. It follows that each atom must have an extremely small mass. However, it is still possible to find out the relative masses of atoms. Si O Billions of these atoms join to form each tiny grain of sand O
© Boardworks Ltd 2003 “Weighing” atoms: The mass spectrometer + + + + + + + + Atoms are given a + charge These charged atoms (ions) are accelerated past a magnet The deflected ions are detected on a screen or film. The magnet deflects this ion. The lighter the ion the more it is deflected + + + + + + + + + The more mass the atom has, the more nearly it travels in a straight line.
© Boardworks Ltd 2003 Relative Atomic Mass 1 The deflection in the mass spectrometer varies with the mass of the atom. However, this does not tell us the mass in grams. relative atomic mass (RAM)What it tells us is the relative masses of atoms – or relative atomic mass (RAM) Carbon is given a RAM value of 12The element carbon is the atom against which the mass of all other atoms are compared. Carbon is given a RAM value of 12. Relative atomic mass = 12 C
© Boardworks Ltd 2003 Relative Atomic Mass 2 The lightest atom is hydrogen. It has one twelfth the mass of carbon and so has a RAM of 1. Magnesium is twice as heavy as carbon. It has a RAM of 24. Mg C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H C 24 x 1 = 12 x 2 1 x 12 = 12 x 1
© Boardworks Ltd 2003 Relative Atomic Mass The Table shows the mass of various atoms relative to carbon. Calculate their relative atomic mass. ElementSymbolTimes as heavy as carbonR.A.M HeliumHeone third BerylliumBethree quarters MolybdenumMoeight KryptonKrseven OxygenOone and one third SilverAgnine CalciumCathree and one third 4 9 96 84 16 108 40 Activity
© Boardworks Ltd 2003 Even Smaller Particles! For some time people thought atoms were the smallest particles and that they could not be broken into anything smaller. We now know that atoms are themselves made from even smaller and simpler particles. These particles are –Protons –Neutrons –Electrons
© Boardworks Ltd 2003 How Are the Particles Arranged? Protons, neutrons and electrons are NOT evenly distributed in atoms. The protons and neutrons exist in a dense core called the nucleus. Around the outside are very thinly spread electrons. These electrons exist in layers called shells. The Nucleus a dense core of protons and neutrons containing nearly all the mass of the atom ‘Shells’ of electrons electrons are really very very tiny so the atom is mostly empty space.
© Boardworks Ltd 2003 The Atom: Check It Out! Draw a labelled diagram of the atom showing the nucleus and labelling protons, neutrons and electrons
© Boardworks Ltd 2003 Properties of Sub-atomic Particles There are two properties of sub-atomic particles that are especially important: –Mass –Electrical charge ParticleCharge Relative Mass Protons+11 Neutrons01 Electrons0.0005 Element atoms contain equal numbers of protons and electrons and so have no overall charge
© Boardworks Ltd 2003 Atomic Number alwaysThe atom of any particular element always contains the same number of protons. E.g. –Hydrogen atoms always contain 1 proton –Carbon atoms always contain 6 protons –Magnesium atoms always contain 12 protons The number of protons in an atom is known as its atomic number. It is the smaller of two numbers shown in most periodic tables 12 C 6
© Boardworks Ltd 2003 How Many Protons? Here is some data about elements taken from the Periodic Table. What is the atomic number of the elements? 23 Na 11 56 Fe 26 119 Sn 50 19 F 9 27 Al 13 11 26 50 9 13 Activity
© Boardworks Ltd 2003 How Many Protons? Note that any element has a definite and fixed number of protons.Note that any element has a definite and fixed number of protons. If we change the number of protons in an atom then this changes that atom into a different element. is very rareChanges in the number of particles in the nucleus (protons or neutrons) is very rare. It only takes place in nuclear processes such as radioactive decay, nuclear bombs or nuclear reactors.
© Boardworks Ltd 2003 Mass Number The mass of each atom results almost entirely from the number of protons and neutrons that are present. (Remember that electrons have a relatively tiny mass). The sum of the number of protons and neutrons in an atom is the mass numberThe sum of the number of protons and neutrons in an atom is the mass number. AtomProtonsNeutronsMass Number Hydrogen101 Lithium347 Aluminium131427
© Boardworks Ltd 2003 Mass Number Calculate the mass number of the atoms shown. AtomProtonsNeutronsMass Number Helium22 Copper2935 Cobalt2732 Iodine5374 Germanium3241 4 64 59 127 73 MASS NUMBER = Number of protons + number of neutrons Activity
© Boardworks Ltd 2003 How Many Neutrons Calculate the number of neutrons in these atoms. AtomMass Number Atomic Number Number of Neutrons Helium42 Fluorine199 Strontium8838 Zirconium9140 Uranium23892 Number of Neutrons = mass number - atomic number 2 10 50 51 146 Activity
© Boardworks Ltd 2003 How Many Neutrons 2 It is not strictly true to say that elements consist of one type of atom. Whilst atoms of a given element always have the same number of protons, they may have different numbers of neutrons. isotopes.Atoms that differ in this way are called isotopes. Remember: The number of protons defines the element
© Boardworks Ltd 2003 How Many Neutrons 3 Isotopes are virtually identical in their chemical reactions. (There may be slight differences in speeds of reaction). This is because they have the same number of protons and the same number of electrons. The uncharged neutrons make no difference to chemical properties but do affect physical properties such as melting point and density.
© Boardworks Ltd 2003 Isotopes: Carbon Natural samples of elements are often a mixture of isotopes. About 1% of natural carbon is carbon-13. Protons Electrons Neutrons C 12 6 99% C 13 6 1% 666666 667667
© Boardworks Ltd 2003 Isotopes: Hydrogen Hydrogen exists as 3 isotopes although Hydrogen-1 makes up the vast majority of the naturally occurring element. H 1 1 H 2 1 H 3 1 Protons Electrons Neutrons Hydrogen Protons Electrons Neutrons (Deuterium) Protons Electrons Neutrons (Tritium)
© Boardworks Ltd 2003 Isotopes: Chlorine About 75% of natural chlorine is 35 Cl the rest is 37 Cl. Cl 35 17 75% 17 Protons Electrons Neutrons 17 18 Protons Electrons Neutrons 17 20 Cl 37 17 25%
© Boardworks Ltd 2003 Isotopes of Oxygen Almost all of natural oxygen is 16 O but about 0.2% is 18 O. Produce a Table showing the particles in each isotope. Protons Electrons Neutrons 16 O 8 Oxygen-18Oxygen-16 8 8 8 Protons Electrons Neutrons 8 8 10 Activity
© Boardworks Ltd 2003 Isotopes and Relative Atomic Mass Many natural elements are a mixture of isotopes. This means that when we react atoms of an element we are using a mixture of atoms with different mass numbers. The relative atomic mass given in the periodic table takes account of this. E.g.. For 100 atoms of chlorine: Mass of 75 atoms of Chlorine 35: 75 x 35 =2625 Mass of 25 atoms of Chlorine 37: 25 x 37 =925 Total = 3550 35.5 Average(divide by 100)= 35.5
© Boardworks Ltd 2003 Relative Atomic Mass Bromine contains 50.5% bromine-79 and 49.5% bromine-81. Calculate the relative atomic mass of natural bromine showing your working. Egg. For 100 atoms of bromine: Mass of 50.5 atoms of bromine 79: 50.5 x 79 =3989.5 Mass of 49.5 atoms of bromine 81: 49.5 x 81 =4009.5 Total = 7999 Average(divide by 100)= 80 (3 s.f.) Activity
© Boardworks Ltd 2003 How Many Electrons The atoms of any element have an equal number of protons and electrons. AtomProtonsNeutronsElectrons Helium222 Copper293529 Cobalt273227 Iodine537453 Germanium324132..and so overall charge equals zero
© Boardworks Ltd 2003 How Many Electrons Fill in the blank columns AtomProtonsNeutronsElectronsAtomic number Mass Number Boron56 Potassium1920 Chromium2428 Mercury80121 Argon1822 5511 19 39 24 52 80 201 18 40 Note – atomic number is defined as the number of protons rather than electrons because atoms can lose (or gain) electrons but do not normally lose protons Activity
© Boardworks Ltd 2003 Activity Drag the statements at the top onto the correct side of the table
© Boardworks Ltd 2003 Activity Drag the statements at the top onto the correct side of the table
© Boardworks Ltd 2003 Summary: The atom so far! The nucleus. Dense: contains nearly all the mass of the atom in a tiny space. Made up of protons and neutrons. Has a positive charge because of the protons. The electrons. Exist thinly spread around the outside of the atom. Very small and light. Negatively charged. Exist in layers called shells. Can be lost or gained in chemical reactions.
© Boardworks Ltd 2003 How Are Electrons Arranged? Electrons are not evenly spread. The exist in layers known as shells. electron configuration.The arrangement of electrons in these shells is often called the electron configuration. 2nd Shell 1st Shell 3rd Shell 4th Shell
© Boardworks Ltd 2003 How Many Electrons per Shell? Each shell has a maximum number of electrons that it can hold. 1st Shell: 2 electrons 2 nd Shell: 8 electrons 3 rd Shell: 8 electrons The maximum
© Boardworks Ltd 2003 Which Shells Do Electrons go into? Opposites attract. Protons are + and electrons are – charged. Electrons will occupy the shells nearest the nucleus unless these shells are already full. 1st Shell: Fills this first 2 nd Shell: Fill this next 3 rd Shell: And so on
© Boardworks Ltd 2003 Working Out Electron Arrangements 1.How many electrons do the element atoms have? (This will equal the atomic number). 2.Keeping track of the total used, feed them into the shells working outwards until you have used them all up. 1st Shell: Fills this first 2 nd Shell: Fill this next Drawing neat diagrams helps you keep track!
© Boardworks Ltd 2003 The Electrons in Carbon
© Boardworks Ltd 2003 The Electrons in Neon
© Boardworks Ltd 2003 The Electrons in Silicon
© Boardworks Ltd 2003 Electrons in Phosphorus
© Boardworks Ltd 2003 The Electrons in Argon
© Boardworks Ltd 2003 The Electrons in Sodium
© Boardworks Ltd 2003 The Electrons in Fluorine
© Boardworks Ltd 2003 The Electrons in Aluminium
© Boardworks Ltd 2003 The Electrons in Nitrogen
© Boardworks Ltd 2003 The Electrons in Sulfur
© Boardworks Ltd 2003 The Electrons in Oxygen
© Boardworks Ltd 2003 The Electrons in Chlorine
© Boardworks Ltd 2003 The Electrons in Magnesium
© Boardworks Ltd 2003 1+ ion Protons Electrons 1- ion Protons Electrons Ions and Electron Structures 1.Ions are atoms that have either extra electrons added or electrons removed. e.g. Atoms Protons Electrons Lose 1 electron Gain 1 electron So in ions the number of electrons no longer equals the number of protons
© Boardworks Ltd 2003 losingThese are ions formed by the atom losing one or more electrons. cationsThey are called cations. This is because during electrolysis they move towards the cathode. (Or because they are “pussytive”!). equal to the number of electrons that the atom has lostThe charge on the ions is equal to the number of electrons that the atom has lost. In equations the charge is usually shown above and to the right of the symbol. (E.g. Mg 2+ ). Positive Ions Lost 1 e - + Lost 2 e - 2+ Lost 3 e - 3+ It is nearly always metal atoms that lose electrons Ions usually have OUTER electron shells that are either completely full or else empty
© Boardworks Ltd 2003 Na Bye! The Electrons in a Sodium Ion atom In the sodium atom Atomic number = number of protons = 11 Number of electrons = 11 Electron arrangement: 2.8.1 (Incomplete Shell) Na+ Electron lost Electron arrangement: 2.8 (Full Shells) 23 Na 11
© Boardworks Ltd 2003 Mg The Electrons in a Magnesium Ion atom In the magnesium atom Atomic number = number of protons = 12 Number of electrons = 12 Electron arrangement = 2.8.2 (Incomplete shell) Mg 2+ Electron arrangement 2.8 (Full Shells) Bye! 2 electrons lost 24 Mg 12
© Boardworks Ltd 2003 The Lithium Ion Li 3 2 1 1st Shell = 2: full 2nd Shell = 1: not full 2.1 1 How many electrons? How many electrons in the first shell? How many electrons in the second shell? What electron arrangement? How many electrons to lose? New electron arrangement? Include a diagram 2.(0) Bye! Li + 7 Li 3 Activity
© Boardworks Ltd 2003 The Boron Ion B 5 2 3 1st Shell = 2: full 2nd Shell = 3: not full 2.3 3 How many electrons? How many electrons in the first shell? How many electrons in the second shell? What electron arrangement? How many electrons to lose? New electron arrangement? 2.(0) Bye! B 3+ 11 B 5 Activity
© Boardworks Ltd 2003 gainingThese are ions formed by the atom gaining one or more electrons. anionsThey are called anions. This is because during electrolysis they move towards the anode. equal to the number of electrons that the atom has gainedThe charge on the ions is equal to the number of electrons that the atom has gained. In equations the charge is usually shown above and to the right of the symbol. (E.g.. O 2- ). Negative Ions. Gain 1 e - - Gain 2 e - 2- Gain 3 e - 3- It is nearly always non-metal atoms that gain electrons Ions usually have OUTER electron shells that are either completely full or else empty
© Boardworks Ltd 2003 The Electrons in a Sulphide Ion. atom In the sulphur atom Atomic number = number of protons = 16 Number of electrons = 16 Electron arrangement: 2.8.6 (incomplete shell) Electron arrangement 2.8.8 (Full shells) 2 electrons gained SS 2- 32 S 16
© Boardworks Ltd 2003 The Electrons in a Fluoride Ion. atom In the fluorine atom Atomic number = number of protons = 9 Number of electrons = 9 Electron arrangement: 2.8.7 (incomplete shell) Electron arrangement 2.8.8 (Full shells) 1 electron gained FF 2- 19 F 9
© Boardworks Ltd 2003 The Oxide Ion 16 O 8 O 8 2 6 1st Shell = 2: full 2nd Shell = 6: not full 2.6 2 How many electrons? How many electrons in the first shell? How many electrons in the second shell? What electron arrangement? How many electrons to gain? New electron arrangement? 2.8 O 2- Activity
© Boardworks Ltd 2003 Drag the words at the top to their correct places in the sentences.
© Boardworks Ltd 2003
1.Which of the following is not a sub- atomic particle? A.Proton. B.Isotope. C.Neutron. D.Electron.
© Boardworks Ltd 2003 2.The element Cobalt has a relative atomic mass of 59 and an atomic number of 27. Which of these is a true statement about each neutral cobalt atom? A.It contains 59 neutrons. B.It contains 27 electrons. C.It contains 32 protons. D.It contains equal numbers of neutrons and electrons.
© Boardworks Ltd 2003 3.The Periodic Table displays iron as shown below. This indicates that Fe atoms: A.contain 56 neutrons. B.contain 30 electrons. C.contain 26 protons. D.contains more protons than neutrons. 56 Fe 26
© Boardworks Ltd 2003 4.Bromine consists of a mixture of two isotopes: Bromine-79 and Bromine-81 Which of the following is true: A.Both isotopes contain 35 protons. B.Bromine 79 contains 46 neutrons. C.Bromine 81 contains 44 neutrons. D.Bromine-81 is more reactive than bromine- 79. 80 Br 35
© Boardworks Ltd 2003 5.Natural boron consists of approx. 20% boron-10 and 80% boron-11. What will the relative atomic mass of natural boron will be? A.10.0 B.11.0 C.10.5 D.10.8 ?B5?B5
© Boardworks Ltd 2003 6.Which answer best describes the shell arrangement of the electrons in a sodium atom? A.2,8,1. B.2,2,7. C.2,8,8,3. D.2,8,8,1. 23 Na 11
© Boardworks Ltd 2003 7.Which answer best describes the shell arrangement of the electrons in an oxygen atom? A.2,8,6. B.2,8,8. C.2,8. D.2,6. 16 O 8
© Boardworks Ltd 2003 8.Which of these elements will have electron shells that are either full or empty (i.e. not partially full)? 14 N 7 A 40 Ar 18 B 40 Ca 20 C 27 Al 13 D
© Boardworks Ltd 2003 9.Which answer best describes the shell arrangement of the electrons in an oxide ion O 2- ? A.2,8,6. B.2,8,8. C.2,8. D.2,6. 16 O 8
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