Chem class(18apr)
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Transcript of Chem class(18apr)
Electron configuration
11
NaSodium
E.C= 2.8.1
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
2.8.1 2.8.4 2.8.5 2.8.6 2.8.7 2.8.82.8.2 2.8.3
2.8.8.1 2.8.8.2
1 2
Group 1
Group2
Group 13
Group 14
Group 15
Group 16
Group 17
Group 18
Period 1
Period 2
Period 3
Period 4
1 2
3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18
19 20
Group• For elements with 1 to 2 valence electrons
Group number of element= the number of valence electrons
• For element with 3-8 valence electrons,
Group number of element= the number of valence electrons +10
Period
• The period number of an element = the number of shells occupied with electrons
Arrangement of elements
a) A group is a vertical column.b) 8 groups ( all the elements in a group have
almost the same chemical properties and slightly different physical properties ) Group 1 – alkali metal Group 2 – alkali earth metal Group 17 – halogen Group 18 – noble gas
c) Biggest group – transition metalsd) Horizontal row is a period.
e) Arrange according their proton number
f) Elements with similar properties are arranged in groups.
g) The electrons in the outer most orbit of an atom are called the valence electrons.
h) All the elements in the same group have the same number of valence electrons.
First person to write the list consists of 33 elements.
Classified element into 4 groups.
•Metals
•non-metals
Classified elements into groups of 3 with similar chemical properties(triads)
Chemical properties
Atomic mass
Element in the triad Relative atomic mass
Lithium 7
Sodium 23
Potassium 39
• Arranged known elements into increasing atomic mass order.
• Plot a graph of atomic volume vs atomic mass.
• Showed that the properties of elements were in a periodic pattern with their atomic mass.
• Arranged the elements with similar chemical
properties into groups.• Left empty spaces for element
which have yet to be discovered.
• Studied the X-ray spectrum.
• Determine the proton number
• Rearranging the elements in
order of increasing proton
number
•Andy lau’s Dog
Jump, Lorry Men
Happy
Remember the 20 elements of
periodic table
H He
Little Belly Boy Come Near Oreo For Nutrition
Naughty Man And Silly People Should Consume A lot of
Kentucky Combo
GROUP 18The Noble Gases
Group 18 Elements
1. Noble gas
2. Make up almost 1% of the air
3. There are helium, neon, argon, krypton, xenon, radon.
4. All the noble gases do not:
Dissolve in water
Conduct electricity
Conduct heatstable
Group 18 Elements
5. Monoatomic gases at room temperature
6. All the noble gases have low m.p and low b.p. It is due to their very weak intermolecular force of attraction. (Van der Waals).
7. Boiling point, b.p increases down the group
8. Melting point, m.p increases down the group
9. Very low density ( weak intermolecular forces).
10.Density increases down the group. (relative atomic mass increase more than volume.
Elements Radius M.p B.p Density
He
Ne
Ar
Kr
Xe
Rn
DOWN THE GROUP
Inert property
1. Low reactivity. 2. Exist as monoatoms.3. Helium has 2 electrons in the outer most shells.
(duplex electron configuration)4. Other noble gases have 8 electrons in their outer
most shells. (octet configuration)5. All the outer most shells are fully filled. (stable)6. They do not accept anymore electrons. Do not donate Do not accept Do not share
Helium
• Helium is less dense than air, so it’s great for all kinds of balloons.
Group 18—Helium
Mixed with oxygen for deep sea
diving
Fill up balloons and air ships
Neon
• Used in advertisement boards
Group 18—Neon
Argon
• To fill light bulbs to prevent the filament from burning
Group 18—Argon
• To fill photographic flash lampsGroup 18—Krypton
• Used in the brightest bulb in lighthouse.
Group 18- Xenon
Radon• Used in cancer
treatment
Weekend assignment
• Look though Group 1 (Alkali Metals)