Inorganic Chemistry & The PT Flashcards
What is the outer shell electron configuration of the halogens?
s2 p5
Room temperature appearance of fluorine
Yellow gas
Room temperature appearance of chlorine
Green gas
Room temperature appearance of bromine
Brown liquid
Room temperature appearance of iodine
Dark grey solid
Describe the trend in boiling points down group 7
Boiling points increase: number of electrons increase; more London forces; more heat energy needed to break these intermolecular forces
Electronegativity def
The ability of an element to draw a pair of bonding electrons towards itself in a covalent bond
Describe the trend of electronegativity down group 7
Electronegativity decreases: more protons means an increasing nuclear charge should attract outer electrons more; number of electron shells increases and so there is more shielding; atomic radius increases then means less nuclear attraction for outer electrons
Describe the trend of atomic size in group 7
Increases: greater atomic radius means more electrons; more electron shells so distance between outer electrons and nucleus increases
Describe the trend of ionic size down group 7
Increases: these ions (anions) are larger than atoms; added electrons to the same nuclear charge causes repulsion from other electrons, expanding the radius
Describe the trend of reactivity in group 7
Decreases: decreasing tendency to gain electrons; increasing nuclear charge as more protons should attract outer electrons more; but more electrons means more sheets and shielding; so atomic radius increases; less positive nuclear charge is experienced by outer electrons
Oxidising agents def + eg
Something that causes other substances to oxidise and is itself reduced e.g. Group 7 elements readily accept an electron to form negative ions
What is the trend in oxidisation for group 7?
Decreases: fluorine is a strong oxidising agent whereas iodine is fairly weak
What is the half equation for group 7 elements?
Reduction reaction: X2 + 2e- —> 2X-
Displacement reactions def (in group 7)
When a more reactive halogen displaces a less reactive one from its halide salt
How do halogens displace each other?
Cl2 oxidises 2Br- to Br2 and 2Cl-
Cl2 oxidises 2I- to I2 and 2Cl-
Br2 oxidises 2I- to I2 and 2Br-
Iodine does not react with bromides or chlorides
Solubility of halogens
All halogens dissolve readily in non-polar solvents; solute and solvent molecules have the same type of intermolecular attraction; new attractions are able to replace the previous ones (like dissolves like); only slightly soluble in polar molecules of water
Colour of halogen solutions in water
Cl - pale green
Br - orange
I - pale brown
Colour of halogen solutions in cyclohexane
Cl - pale green
Br - orange
I - violet
Halogen reaction with metals (equation eg)
Ha2 + 2Me —> 2MeHa
Produces metal halides
Disproportionation reaction def
When the same species is both oxidised and reduced in a reaction
Health benefits of chlorine use in water
Treatment of water in making it potable; powerful oxidising nature; effective disinfectant and kills bacteria; prevent a spread of water-borne diseases.
Bleach; decolourises water
Describe the trend in first ionisation energies in group 2
Decreases: atomic radius increase as number of electron shells increases; more shielding so weaker attraction between outer electrons and nucleus; less energy needed to lose outer electrons. The increase in number of protons is negated by increase in atomic charge and shielding.