Tok- Explain Why Knowledge Cannot Be Inherited Essay

710 Words3 Pages
Topic 3- Periodicity ------------------------------------------------- 3.1 The Periodic Table 3.1.1 Elements increase in atomic number across each period, and down each group. The history is boring and pointless (but then, I’ve never been much of a history fan) and can probably be ignored. *Mendeleev turns in his grave* 3.1.2 Group – the columns going down. Period – the rows going across. 3.1.3 Group = number of valence electrons in the atom. Period = number of main electron shells…s, p , d and f blocks as described above. ------------------------------------------------- 3.2 Physical Properties 3.2.1 Li->Cs (down the alkali metals) Atomic radius increases due to increased electron shielding. The outer electron is in an energy level that is progressively further away away from the centre of the nucleus. 'Ionic radius decreases'? due to the fact the valence electron has been removed from the outer shell. This allows the protons within the nucleus to have a greater attraction towards the electrons because there is now one extra proton more compared to the amount of electrons. There is also one fewer energy level, because the outer shell has effectively been removed.' Ionisation energy decreases due to increased electron shielding. Melting/boiling point decreases due to increased electron shielding (hence decreased forces). Electronegativity decreases due to increased shielding (hence decreased attraction for outer electrons). F->I (Down the halogens) Atomic radius increases due to increased electron shielding. Ionic radius increases due to increased electron shielding. Ionisation energy decreases due to increased electron shielding. Melting/boiling point increases due to increased number of electrons->increased london dispersion forces. Electronegativity decreases due to increased shielding -> decreased attraction for outer

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