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