Group 7 (17), the halogens
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What type of elements make up Group 7 of the Periodic Table?
Group 7 elements are diatomic molecules, halogens non -metals
In what form do Group 7 elements exist naturally?
Halogens exist as diatomic molecules, such as F2, Cl2, Br2 and I2
What trend is observed in the appearance of the halogens going down Group 7?
The halogens get darker in colour and denser as you go down the group
At room temperature, what is the appearance/state of fluorine, chlorine, bromine and iodine?
Fluorine is a pale yellow gas Chlorine is a greenish gas Bromine is a red - brown liquid Iodine is a black solid
Why are the properties of fluorine untypical compared to the other halogens?
Fluorine has an unusually weak F-F bond due to repulsion between non - bonding electrons, which are very close together because of fluorine’s small atomic size
What causes the F-F bond to be weaker than expected? (small - repu. - lp. of e- - wkn. bond)
The small size of fluorine atoms leads to repulsion between lone pairs of electrons, weakening the bond
How does atomic size change going down Group 7, and why? (inc. bcse. ech. elmnt. - extra. elctrn. shll. inc. dstnc. btwn. outrmst. E- + nuc. - rdcng. elctrstc. atrctn. - inc. elctrns. shls. otwgh. atrctn. nuc.)
Atomic size increases because each element has an extra electron shell, increasing the distance between the outermost electrons and nucleus, reducing the electrostatic attraction, so the increased electron shells outweighs the attraction of the nucleus
What is electronegativity? (msr. ablty. atm. atrct. shrd. pr. elctrns. twrds. itslf. - cvlnt. bnd.)
Electronegativity is a measure of the ability of an atom to attract a shared pair of electrons towards itself in a covalent bond
What factors affect electronegativity?
• the nuclear charge • atomic radius (atom size) • electron shielding
Why does electronegativity decrease going down Group 7? (atms. get lrgr. - prd. elctrns. frthr. frm. nuc. + exprnce. > shldng, rdcs. atrctn. btwn. nuc. + prd. elctrns. dspte. inc. nuclr. chrge.)
As atoms get larger, the paired electrons are further from the nucleus and experience more shielding This reduces the attraction between the nucleus and paired electrons, despite the increasing nuclear charge
How does the bonding in hydrogen halides illustrate the trend in electronegativity? (shrd. elctrns. H-X bnd. frthr. frm. hlgn. nuc. gng. dwn. grp. shwng. inc. shldng. + rdcd. elctrngtvty.)
In hydrogen halides, the shared electrons in the H-X bond are further from the halogen nucleus going down the group, showing increased shielding and reduced electronegativity
How do melting and boiling points change going down Group 7? (inc. dwn. grp. bcse. lrgr. mlcls. - >electrns. ldng/ strngr. vdW frcs. btwn. mlcls. rqre. >enrgy. ovrcme.)
Melting and boiling points increase down the group because larger molecules have more electrons, leading to stronger van der Waals forces between molecules, which require more energy to overcome
What is the relationship between the volatility and boiling point in Group 7 elements?
The lower the boiling point, the more volatile the element
What is the trends in ionisation energies as you go down group 7? (dwn. grp. IE dec. - bcse. atms. bgr. + hve. mre. shldng. - lds. wkr. atrctn. btwn. nuc. + elctrns. outr. shll.)
As you go down group 7, ionisation energy decreases. This is because the atoms get bigger and have more shielding. This leads to weaker attractions between the nucleus and electrons in the outer shells