Science NCEA L1 1.7 Metals and Their Uses

1. Science NCEA L1 1.7 Metals and Their Uses GZ Science Resources 2012

2. Atomic Structure The nucleus contains protons (p) and neutrons (n). Electrons (e) orbit the nucleus, arranged in shells or energy levels. Electron -ve Nucleus Neutron N P N P N N P Proton +ve P P P N N This is known as the Bohr model. Shell 1 Shell 2 GZ Science Resources 2012

3. Electron numbers in shells Maximum numbers of electrons in each shell are: -2 in the first shell (nearest the nucleus), -8 in the second shell, -8 in the third shell (before the fourth shell starts to fill) GZ Science Resources 2012

4. Atom Charges Protons are positively charged; electrons are negatively charged; neutrons have o electrical charge. Atoms have no overall charge because the number of protons = number of electrons. • All matter is made up of atoms. Atoms consist of protons, neutrons and electrons. • The charges of protons and electrons are equal and opposite. GZ Science Resources 2012

5. Atom Summary GZ Science Resources 2012

6. Atomic Number Atomic number = number of protons. Symbol = Z The atomic number is unique for each element. An atom has the same number of electrons as protons. The periodic table is arranged in order of an elements atomic number. GZ Science Resources 2012

7. Mass Number Mass number = number of protons and neutrons. Symbol = A The Mass number is the number of protons + number of neutrons. The Mass number is close to double of the Atomic number. An isotope is an element with a different Mass number because it has more or less neutrons than normal. Mass number GZ Science Resources 2012

8. Isotopes Why is the Mass Number not always a whole number? Most elements have a proportion of their atoms that exist as isotopes – Atoms that have less or more neutrons. The Mass number is worked out by finding the Mass number of all the isotopes and averaging them by heir proportions. Carbon and C14 isotope GZ Science Resources 2012

9. Element Symbols Elements consist of only one type of atom. Each element can be represented by a chemical symbol. Most symbols are one or two letters, formed from the name of the element,e.g. Hydrogen H, or Helium He. The first letter of the symbol is always a capital letter. Any other letters are lower case.e.g. Helium is He not HE If the symbols are not based on a elements English name then it is most likely to be based on it’s Latin name, the original language of Science. SJ

10. Electron configuration A shorthand way of describing the way electrons are arranged in an atom is called the electronic configuration. The information for the number of electrons is found by an elements Atomic Number (number of electrons = number of protons in a neutral atom). Each shell is filled to its maximum capacity, starting with the lowest shell first (shell number 1 or M shell). The shells are separated by a comma. The shells are filled until all the electrons are placed. The total of the electronic configuration must equal the atomic number in an atom Atomic number 12 Mg 24 2, 8, 2 First shell, second shell, third shell

11. Structure of the Periodic Table The columns (downwards) of a periodic table are called groups. The rows (across) of a periodic table are called periods. Elements in the same group all have the same number of electrons in their outer (or valence) shells. Elements in the same period all have the same number of shells of electrons in their atoms GZ Science Resources 2012

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13. Group One – Alkali Metals These elements are called the Alkali Metals. They are all very reactive with air and, especially so, water. The further down the group the more reactive they are. Hydrogen is not included in this as it does not share similar properties with the rest of the elements.

14. Group Two – Alkaline Earth Metals These elements are called the Alkali Earth Metals. They all react with air, but are less reactive than group 1. GZ Science Resources 2012

15. Metals and Non-Metals Elements can be classified as metals or non-metals. A few elements are called semi-metals or metaloids (e.g. boron and silicon), because they show some, but not all, of the properties of metals. GZ Science Resources 2012

16. Metals and Non-Metals

17. Metals Metals can be distinguished from non-metals by their physical properties; they are strong, dense, shiny solids that can be worked into different shapes. They are good conductors of heat and electricity. GZ Science Resources 2012

18. Physical properties of Metals GZ Science Resources 2012

19. Sodium Sodium is a member of the alkali metal family with potassium and lithium. Sodium's big claim to fame is as one of two elements in your table salt (the other element is chlorine). Even though humans have been using sodium for thousands of years, it was not isolated until 1807 by a chemist named Davy. When you purify sodium, you actually wind up with a silvery bright metal that is quite soft and malleable. Sodium is one of the few metals that will float when it is placed in water. Its atomic mass is less that water's atomic mass. GZ Science Resources 2012

20. Calcium Calcium (Ca) is an important element that helps your bones stay strong and able to support your weight. Your nervous system also uses calcium to help transmit impulses through your body. Humans have known about calcium and calcium containing compounds since before the Greeks and Romans. When you think of calcium, you might think of a white powder, but when purified, calcium is a hard silver-colored metal. You will find calcium in the second column of the period table with other elements including beryllium and magnesium. The elements in that column make up the alkali earth metal family. GZ Science Resources 2012

21. Magnesium Humans have used magnesium, like many other simple elements, for hundreds of years. It wasn't until 1808 that a chemist named Davy isolated and purified the metal. The reason it took so long to isolate magnesium is that it is always found with other elements in nature. Located in the second column of the periodic table, magnesium is in the family of alkali earth metals with calcium and beryllium. When purified, magnesium is a very light and silvery metal. Its lightness makes it perfect for use in many other metal alloys to increase strength without increasing the weight of the structure. Magnesium is also an important element in your diet. Both you and plants need magnesium to live and be healthy. It is called a trace metal. GZ Science Resources 2012

22. Aluminium You are probably very familiar with the metal aluminum. Many of you wrap your sandwiches everyday with aluminum foil. On the other hand, many of your families cook with the foil. The metal is a silvery white color and very reflective. Another great trait of aluminum is that it is not toxic. So cook and eat away, the aluminum foil will not get you sick. When aluminum is combined with other metals it becomes very strong. It is so strong that engineers use it to build planes and ships. Even though humans have been using the metal for thousands of years, it was not until 1807 that Davy named the metal. It took another twenty years before it was purified and isolated by a chemist named Wohler. Aluminum is located in the same column of the periodic table with boron. GZ Science Resources 2012

23. Zinc Zinc is another of the useful metals that we use every day. It's one of those elements humans have been using for thousands of years. You'll find zinc in minerals, alloys, and even your body. It wasn't ever really discovered, zinc was used long ago when ancient peoples were first creating brass. In 1746, Marggraf was isolated and described zinc as a separate metal. Zinc is normally found as a part of larger mineral compounds. When isolated, it is a very shiny, bluish-white metal. Unfortunately, it is not as malleable as its neighbor copper is and has fewer uses. Zinc's location at the end of the transition metals shows that is has a completely filled third electron shell. GZ Science Resources 2012

24. Iron There is a whole period of time named after this element (Iron Age). Humans have been working with iron for thousands of years. Iron is found all over the Earth and the Universe. You have iron in your computer, your desk, and even your body. When purified, iron is a grayish, shiny metal. It oxidizes easily and the resulting compound is known as rust (iron oxide). Rust is a reddish-brown color. It's technically another transition element and another metal. While you may think of iron as a magnetic metal, not all forms of iron are magnetic. GZ Science Resources 2012

25. Copper Copper is one of the metals that has been a part of civilization for thousands of years. Iron, copper, gold, and silver have all been used in one form or another. While you might not think of copper being used for anything but coins, it is a key element in the creation of bronze. Copper has been in use for so long because it is found by itself as a pure element. You could be digging in a mine and come across pure copper in a variety of forms. It's one of those elements that was never really discovered. It has been a part of every step in the development of civilization. The thing we keep discovering is the variety of places copper is used in nature. This transition metal is well known for the two colors that are reddish when pure and a turquoise color when copper is oxidized. GZ Science Resources 2012

26. Lead Lead is a soft, heavy, toxic and malleable metal, lead is bluish white when freshly cut but tarnishes to dull gray when exposed to air. Lead is used in building construction, lead-acid batteries, bullets and shot, and is part of solder, pewter, and fusible alloys. Lead has the highest atomic number of all stable elements Like mercury, another heavy metal, lead is a potent neutrotoxin which accumulates in soft tissues and bone over time. GZ Science Resources 2012

27. Metal Bonding Metals atoms are arranged as positive ions held in place in ordered layers by strong attractive forces, forming a lattice. - this gives metals strength. The ions are packed tightly together - this makes metals dense GZ Science Resources 2012

28. Metal Bonding Electrons from the outer shells of the metal atoms move freely throughout the lattice. - this makes metals excellent conductors of heat and electricity GZ Science Resources 2012

29. Metal Bonding Layers of ions can slide over each other without breaking- this makes metals malleable and ductile GZ Science Resources 2012

30. Metal Bonding Free moving electrons in the metallic lattice strongly absorb light, then quickly reflect nearly all of it. - This makes metals shiny, called lustre. GZ Science Resources 2012

31. Metal Uses The use of a metal depends on its chemical and physical properties GZ Science Resources 2012

32. Metal Reactivity Metals react with other chemicals with varying speed or not at all. Differences in reactivity are shown in the reactivity series of metals. Reactivity series Unreactive very reactive Metals will react faster if they are more reactive – more reactive metals give up their electrons more readily to react with other chemicals Pt >Au>Ag>Cu>Pb>Sn>Fe>Zn>Al>Mg>Ca>Li>Na>K>Rb>Cs GZ Science Resources 2012