Periodicity. What comes next..... Make sense of the next shape.....
Post on 01-Apr-2015
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Periodicity
What comes next .....
Make sense of the next shape .....
Same as the periodic table
• Groups are vertical columns• What do groups share in common?
• How about the rows?
Rows are called PERIODS
• Periods have properties vary in a fairly regularly way from left to right – repeated in next period (PERIODICITY)
• Anyone think of any patterns• /trends left to right?
Metal to non-metal
• Thus the ELECTRIC CONDUCTIVITY decreases as you go across the table (metals are conductors to non-metals , insulators)
• Why?
Your Turn
• Groups given out• In your groups construct a graph
that illustrates the trend of your property.
• Remember someone will need to explain why.
Density
Physical Properties - Density
• DENSITY (mass in a set volume) of the atom varies.
• Metals are HIGHLY DENSE (compacted close together, allowing e-s to move easily)
• Non metals are LESS DENSE
Melting and boiling points
Melting and boiling points
• When things are melted or boiled the bonds between them need to be overcome
• Strength of bond leads to boiling/melting temp.
• High temp = strong bond• Stronger bond in metals, than non-metals
Atomic Size?• Determined by the space the e- take up
• Think about what you know – predict what happens left to right .......
• Atomic size decreases across table because e- fill in existing shell & 1 more P+ thus hold in closer
Chemical formulae periodicity
• i.e how many Cl & O to make a compound across the table?
• Think of e- arrangement i.e. Li 1 Cl, Be needs 2 Cl etc.
• Different due to chemicals
Electronegavity• Electronegativity is the attraction an atom has
on an e- when chemically combined with another atom
• i.e Gp 7 highest• Nobel gases 0
Ionisation Enthalpies
Ionisation Enthalpies
• Ionisation enthalpy is the amount of energy needed to remove e-’s from atom
• First ionisation enthalpy = 1st outermost e- to be removed
• Increases enthalpy across a period - why do you think this happens?
Trends
• Look at what is different – down a gp shell of e-
• Across a period – the atomic number (P+ ) and thus e-
• 3 main factors you need to consider–charge of nucleus–Amount of shielding by inner e-–Distance between outer e- & nucleus
Mendeleev Prediction
• When Mendeleev constructed his periodic table he left gaps in it for new elements & predicted the PROPERTIES that element would have.
• Germanium (Mendeleev called it eka-silicon)Predicted appearance, RAM, density, reaction with water/acid/alkali/oxide & chloride
Who am I • A’s write an element down and now
describe it to your partner in terms of density, mp/bp, atomic radi, oxide & chloride formed – see if they get it right
• Description graphs p238/239/240 Chemical Ideas
• Swap over
Exam Question Tips
• Many times exam papers will ask you about an element that you have not covered – this is so you can apply your knowledge of the rest of the group/period to that case
• Key skills is to learn to read the various graphs• Justify your answer – why will the melting
point decrease?
Write a summary of periodicity, periodic patterns including these
keywords
Electron arrangement
Melting points/boiling points
Trends
Density
Ionisation enthalpies Atomic size
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