Chemistry: C4

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The Periodic Table

  • Elements in the periodic table are arranged in atomic number (proton number)
  • Horizontal = Period and vertical = Group
  • Elements in a group = elements with similar properties
  • Group 1 = Alkali Metals
  • Group 7 = Halogens
  • In the periodic table, metals are on the left, and non-metals are on the right
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Fill in the blanks...

1. Elements are arranged in the periodic table according to their ...............

2. Each row is called a .........., and each ............. is called a group.

3. Groups are elements with .............

4. In the periodic table, metals are on the ..........., and non-metals are on the .............

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Alkali Metals

  • These are metals in Group 1.
  • Properties...
    • soft - you can cut them with a knife
    • shiny - when freshly cut
    • quickly tarnish in moist air - they react with water and oxygen
    • have low density - some float on water
    • react with water to form hydrogen and an alkali solution of the metal, hydroxide
    • e.g. sodium + water ----> sodium hydroxide + hydrogen
  • React vigorously with chlorine and produce colourless crystalline salts called metal chlorine.
  • Melting points vary with proton number in Group 1:
    • Lower proton number = higher melting point
    • Lower proton number = higher boiling point
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1. Name three properties of Group 1 metals.

2. What does a low proton number equal in terms of alkali metals?

3. Complete this word equation:

lithium + ----> + hydrogen

4. Circle the correct words in this passage:

Alkali metals react vigorously with chlorine/sulphur and produce colourful/colourless crystalline gases/salts called metal chlorine/sulphide.

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Balanced Equasions

  • In any chemical equation, there must be the same amount of each element on both sides of the equation. This creates the balance equation.
  • Show the state of products and reactants: solid (s), liquid (l), gas (g), or aqueous solution (aq).

1. Do the word equation -

Potassium + Water ----> Potassium hydroxide + Hydrogen

2. Write down the formulae -

K + H2O ----> KHO + H

3. Balance the equation and add states -

K(s) + H2O(l) ----> HKO(g) + H(g)

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Balance this equation including the states using the three step method:

1. lithium + chlorine ----> .......... + ............

2. ....................... + ................ ----> LiCl + ................

3. ........................+ ................... ----> ......... + ...............

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The Halogens

  • These are non-metals from Group 7
  • Properties...
    • Coloured vapours
    • Bleach vegetable dyes and kill bacteria
    • They are toxic to humans
    • Molecules made from two atoms; they are diatomic
    • React with metals to create crystalline compounds, salts.
      • Halides of alkali metals are colourless salts, e.g. potassium
    • Compounds of group 1 elements - MX ( M = metal and X = halide)
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True or False? - If false, give the correct statement.

1. Halogens are from Group 1.

2. They are non-metals.

3. Their molecules are diatomic.

4. Halogens react with non - metals to create colourless salts.

5. The compound of Group 1 elements have the formula MX.

(What does M and X stand for?)

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Atomic Structure

  • Atoms are made of subatomic particles:
    • Protons - charge of +1
    • Neutrons - charge of 0
    • Electrons - charge of -1
  • Number of protons = atomic number (as arranged in the periodic table)
  • Number of protons = number of electrons = no overall charge
  • Electrons arranged in shells (or energy levels) around the nucleus
    • Up to 2 electrons in shell 1
    • Up to 8 electrons in shell 2
    • Up to 8 electrons in shell 3
  • Atomic number of sodium = 11
    • This means there are 11 electrons in a sodium atom.
    • There will be 2 electrons in the first shell, 8 in the second, and 1 in the third.
    • This can be written 2.8.1 - this is an electronic configuration.
  • REMEMBER: Shells of an atom fill from the inside to the outside.
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1. Why does an atom have no overall charge?

2. The atomic number of nitrogen is 7. What is the electronic configuration?

3. What are the energy levels in an atom?

4. If the relative atomic mass of magnesium is 24, and the atomic number is 12, how many neutrons does the atom have?

5. In which direction do shells fill up?

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Atomic Structure: Continued

  • Periodic table period = how many shells contain electrons
  • Periodic table group = how many electrons in outer shell
  • That's why elements in the same group have similar properties...they have the same number of electrons in their outer shell

How to work out the electronic structure of an element:

1. See which period it's in and draw that many shells around the nucleus.

2. Work out which group the element is in and draw that many electrons in it's outer shell.

3. Fill in the inner shells according to how many it can hold.

4. Double check by counting how many electrons you have drawn and see if it matches the atomic number.

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Using the method overleaf, draw the electronic structure of these elements:

1. Oxygen

2. Lithium

3. Sulphur

4. Chlorine

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Ionic Bonding

  • Ions are electrically charged particles formed when atoms loose or gain electrons in a reaction between a metal and non - metal.
  • An ionic compound is the product formed.
  • Ionic compounds have high melting and boiling points.
  • Ionic bonds = The strong forces of attraction between oppositely charged ions.

Different elements have different charges depending on whether it is a metal or non - metal.

  • Metals form POSITIVE ions - by loosing electrons
  • Non - metals form NEGATIVE ions - by gaining electrons
  • REMEMBER: When a metal and non - metal react, their aim is to get a full outer shell, the only way to do this is to 'steal' from eachother. A metal has too many electrons, (so it's positive) therefore it gets rid of the ones in its outer shell and the non - metal takes them, because it has too little. Hence, both atoms will now have a full outer shell.
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1. Why do ionic compounds have high melting and boiling points?

2. When are ions formed?

3. Do metals form positive or negative ions? - Why?

4. Do non - metals loose or gain electrons? - Why?

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Ionic Bonding: The Charge of an Ion

How to work out the charge of an ion:

  • For metals, the charge is equal to the number of electrons in its outer shell (or its group number) e.g...
    • Sodium = Na+
    • Magnesium = Mg2+
    • Aluminium = Al3+
  • For non - metals, the charge is equal to the number of electrons it needs to get a full outer shell (or the group number minus eight) e.g...
    • Nitrogen = N3-
    • Oxygen = O2-
    • Chlorine = Cl-
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1. If sodium reacted with chlorine, which element would loose an electron and why?

2. Draw this reaction using electronic structure.

3. The electronic configuration of element X is 2.8.5. What is it's ionic charge?

4. What element is it? And how did you work it out?

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