# Periodicity. What comes next..... Make sense of the next shape.....

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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

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 enthalpy is the amount of energy needed to remove e-’s from atom First ionisation enthalpy = 1 st 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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