Chemical Reactions


Published on

Published in: Education, Technology
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Chemical Reactions

  1. 1. The AtomHistory and Theories All images from Wikipedia unless stated otherwise.
  2. 2. Atom The word atom means indivisible.Indivisible means it cant be broken down into more things. Why not? Is this true for atoms?
  3. 3. John Dalton John Dalton was a British schoolteacher. He said that atoms: 1. Everything is made of atoms.2. Atoms of the same element are exactly alike, and atoms of different elements are different.3. Atoms join with different atoms to make new substances.
  4. 4. J .J . Thomson J. J. Thomson was another British scientist. In 1887 he discovered electrons.Image/s: wikipedia
  5. 5. Plum Pudding Model J J Thompson suggested that electrons were mixed up in theatoms like raisins in a plum pudding.Image/s: wikipedia
  6. 6. Earnest Rutherford Earnest Rutherford was a New Zealander. His famous gold foil experiment showed that atoms must have a dense core. Rutherfords Conclusions: 1. The atom is mostly empty space.2. There is a small, dense, nucleus at the centre of the atom.If an atom was the size of a sports stadium, thenthe nucleus (protons and neutrons) would be thesize of a pinhead in the centre, and the electrons would be orbiting around the outside of the stadium.
  7. 7. Rutherfords Conclusions 1. The atom is mostly empty space.2. There is a small, dense, nucleus at the centre of the atom.
  8. 8. Bohrs ModelBohr (Danish) improved RutherfordsModel by discovering that there are energy levels (called “electron shells”) for electrons.Electrons can only be at set energy levels. Each energy level holds a maximum number of electrons. They are like rungs on a ladder.
  9. 9. Elements The number of protons is called the atomic number. The atomic number tells us which element it belongs to. All the elements can be arranged by atomicnumber in the periodic table. Which elements are these?
  10. 10. The Nucleus Each particle in the nucleus has mass of 1 Atomic Mass Unit (amu).The mass number is the number of protons + the number of neutrons.
  11. 11. Electrons 8A not done Atoms are neutral if they have the same number of electrons as protons.At om can l ose or gain el ect r ons t o becom ions. s e If an at oml oses el ect r on/s, it becom a es _ _ _ _ _ _ _ _ _ _ _ ion because it has m e or _ _ _ _ _ _ _ t han _ _ _ _ _ _ _ _ _ . If an at omgains el ect r ons, it becom a es _ _ _ _ _ _ _ _ _ ion because it has m e or _ _ _ _ _ _ _ t han _ _ _ _ _ _ _ _ .
  12. 12. Electron ShellsElectrons orbit the nucleus in shells. They always fill the inside shell first. The first shell can contain up to 2 electrons.The second shell can contain up to 8 electrons. The third shell can contain up to 8 electrons. The fourth shell can have up to 18 electrons.
  13. 13. IsotopesAll atoms have the same atomic number, which is the number of _________. Atoms of the same element can have a different number of neutrons. 1. Are their atomic numbers the same? 2. Are their mass numbers the same?
  14. 14. AnimationMake as many stable isotopes as possible, and recordthem in the table: Start at the top of a page.Element Name Atomic Number Mass Number Nuclide Symbol
  15. 15. What is an IsotopeIsotopes are atoms with the same number of protons but different numbers of neutrons.Since they have the same number of protons, they belong to the same element.Since they have the same number of electrons, they react the same in chemical reactions. In nature, different isotopes are all mixed up.However, some isotopes are radioactive (give off radiation) and some dont.
  16. 16. Example: IodineIodine has many isotopes, but Iodine-127 is stable and most common. a) How many protons does it have? b) How many neutrons does it have? c) Write it as a nuclide symbol. Iodine is needed by the thyroid, which saves a supply of it. However about two billion people are deficient worldwide. Many countries add but too much is harmful. It is commonly added to salt to prevent
  17. 17. Iodine-131Iodine-131 is another isotope of iodine. It is radioactive (gives off radiation). It is produced in nuclear reactions and released only during nuclear accidents.Since it has the same number of electrons as Iodine-127, the body thinks it is normal iodine, and saves it.There have been about 6000 cases of thyroid cancer since the Chernobyl accident in (present day) Russia.It can be easily prevented by taking pills of Iodine-127, as the body saves the Iodine-127 so it doesnt store any of the harmful Iodine-131.
  18. 18. Uranium IsotopesUranium has two common isotopes: Uranium-235, which is used for nuclear reactors (and weapons) and Uranium-238 is most common. Naturally these are mixed up.What is the difference between the different isotopes of uranium? They cannot be separated using chemistry. How can they be separated?
  19. 19. AnimationMake as many stable isotopes as possible, and recordthem in the table: Start at the top of a page.Element Name Atomic Number Mass Number Nuclide Symbol 1 1 1Hydrogen 1 HHelium 2 3,4 3 2 He , 4 He 2Lithium 3 6,7Beryllium 4 7, 9, 10Boron 5 10, 11Carbon 6 11, 12, 13, 14, 15Nitrogen 7 13, 14, 15, 16
  20. 20. Calculating the Atomic Mass The atomic mass number of an element is an average.76% of Chlorine has an atomic mass number of 35.24% of Chlorine has an atomic mass number of 37. What is the atomic mass number of chlorine?
  21. 21. IonsNeutral atoms have the same number of protons as electrons.Atoms “like” (they cant think) to be neutral. But they “prefer” to have a full outside shell (called a valence shell).Atoms “want” to lose or gain electrons to have a full outside shell. For example, Lithium could either gain ____ or lose _____ electrons.Atoms lose or gain electrons by giving, receiving or sharing them with other atoms. This is called bonding, and is the basis of chemistry.Ions are written as the element symbol with +s or -s to show electrons gained or lost. Eg
  22. 22. Atoms and Ions Element Electrons it “wants” Ion Symbol to Lose or Gain Hydrogen* Lithium Beryllium Oxygen Flourine ArgonAdditional blog note: According to what we learned, hydrogen could either gain or lose 1.To become an ion, Hydrogen will always lose 1 to become H+.Argon does not “want” to lose or gain any, because it already has a full valence shell.
  23. 23. Questions1. Explain what an ion is.2. Explain what is meant by the term “valence shell”.3. What (in terms of ions) do Hydrogen, Lithium andSodium all have in common?4. What (in terms of ions) do Oxygen and Sulfur have incommon?5. What (in terms of ions) do Argon and Neon all have incommon?6. How many electrons does a sodium atom “want” togain or lose, and why? How about a chlorine atom?7. A sodium atom meets a flourine atom and explains herneed (from Q6) and the flourine atom explains hers inturn. What arrangement could they come to? When theydo, what have they made?
  24. 24. Periodic TableAll elements can be arranged in the periodic table by ______________.Rows are called periods. We will learn about them soon. Columns are groups. What is the same about groups of elements?
  25. 25. Grouping the Elements A group is a column (going down) of elements. Elements in the same group usually have the same number of electrons in their outside shell.Groups have similar reactivity. For example, alkali metals are very reactive.
  26. 26. IonsAn ion is an atom which has ________ or________ electrons in order to have a full outer (__________) shell.Atoms which can easily lose or gain up to three electrons in order to have a full ________ shell can form ions.
  27. 27. Ionic BondsIn order to become an ion, an atom needs to findanother atom to give its electrons to or take themfrom. A positive ion and a negative ion then forman ionic bond, making an ionic compound.Example: Sodium Chloride: An excellent image of Sodium Chloride can be found here:
  28. 28. ReviewDraw atomic diagrams for magnesium-24 and chlorine-35.What is the ratio of magnesium atoms to chlorine atoms for it to be balanced?Write the name and the chemical symbol of the ionic compound created.Blog note: Magnesium Chloride is known as“Nigari” in Japanese, and is used to make tofu.An image can be found here:
  29. 29. Use the Cutouts and Make Formula for the Following: Table salt (sodium chloride) Lithium Fluoride Hydrochloric Acid (hydrogen chloride- next unit) Magnesium Chloride Magnesium Oxide Aluminium Oxide Write the chemical formula (eg MgCl2) under each one.Blog note: This was set for homework, and checked before Spring Break. Please make sureyou complete it if you havent already.
  30. 30. Calcium ChlorideCalcium Chloride is a salt used to de-ice roads in cold conditions. 1. What ions do calcium and chlorine make? Explain why. You may use a diagram, but you dont have to. 2. How many of each atom will be needed to make calcium chloride? Explain why. 3. Write the chemical formula for calcium chloride.