Module 3 Flashcards
How are elements in periodic table arranged
By increasing atom/proton number
What is periodicity
Repeating trends in physical and chemical properties
Why do elements of dame group have similar chemical properties
Same number of electrons in outer shell/same electron config
What is first ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Equation for sodiums first ionisation energy
Na (g) —> Na+ (g) + e-
Finish sentence
Ionisation energy is affected by how strongly……. are attracted to ….
Stronger the attraction …. energy required to remove electron so ionisation energy is ….
Electrons
Nucleus
More
High
3 factors affecting attraction between nucleus and electrons
Brief explain why
Nuclear charge: more protons means stronger pull
Atomic radius: distance between outer shell electron and nucleus affects level of attraction
Electron shielding: nucleus and electron attraction partially blocked by inner shell electrons
Why are there large increases in ionisation energy as you jump to different shell
(In same element subsequent further IE)
Big reduction in atomic radius and shielding
Why does first ionisation energy decrease down the group
Increase in nuclear charge is more than cancelled out by increase in atomic radii and shielding which decreases nuclear attraction between nucleus and outer shell electrons so less energy required to remove electron
General trend in 1st ionisation energy across a period
Nuclear charge increases which causes atomic radius to decrease as stronger pull and nuclear attraction between nucleus and outer shell electron increased and require more energy to remove electron
Shielding is same as same shell across period
Explain slight decrease in 1st ionisation energy across period (between some elements)
Ionisation that results in full or half full sets of orbitals require slightly less energy
Explain metallic bonding
Giant lattice structure of close packed metal cations in a sea of delocalised electrons with electrostatic forces
Why are metals insoluble in water
Why do metals conduct electricity in both states
More likely to simply react rather than break apart by solvents
Delocalised electrons act as mobile charge carriers
Explain giant covalent structure
Giant lattice of atoms held by covalent bonds which are strong electrostatic attraction between nuclei and shared/bonded electrons
Why are giant covalent structures insoluble in water
Conduct electricity??
Why does it have high mp/bp
Bonds too strong to pull apart
Electrons localised and no charged particles so cant carry charge
Strong bonds require more energy to break
Explain simple molecular structures
Small groups of covalent bonded atoms with weak intermolecular forces so easy to melt
What are the giant covalent elements in period 2 and 3
B
C
Si
Why does mp drop from group 4 to 5
Why does mo increase from grp 1 to 3
Change from giant to simple structures
Nuclear charge increases so stronger electrostatic attraction in metallic bonding
What is a reducing agent and example
Example of oxidising agent
Reduces other element but itself is oxidised
Eg metals
Eg halogens
Why do trends in reactivity increase down grp 2
1st and 2nd ionisation energy decreases down grp so more reactive
Product of grp 2 oxides and water
Unsaturated: metal and hydroxide ions in solution
Saturated: metal hydroxide solid
Why does solubility of grp 2 increase down the group
Charge is same but mass increases so charge/mass ratio decreases so less electrostatic attraction and easier to pull apart
Approx pH comparison of Mg(OH)2 and Ba(OH)2
Mg is 10
Ba is 13
Ba is more alkaline due to more OH- released in solution
Grp 2 metal and acid product
Salt and hydrogen
Grp 2 metal and water product
Metal hydroxide and hydrogen
Use of grp 2 compounds in our lives
Agriculture: calcium hydroxide added to fields to decrease acidity of soil
Medicine: antacids, calcium carbonate react with HCl in stomach from indigestion
Why does bp increase down group in halogens
Larger molecules so more electrons and stronger London forces so more energy needed to overcome intermolecular forces
Why does reactivity decrease down halogens grp
Atomic radius/shielding increases so less nuclear attraction to attract an electron to join outer shell
2 Disproportionation reactions of Cl
With low quantities of Cl2
1) With water forming HClO and HCl
2) With NaOH forming NaClO, NaCl and water
Benefits and risks of Cl2 in water treatment
Bacteria killed so water borne diseases prevented
Cl2 gas is toxic and a respiratory irritant Chlorinated hydrocarbons (methane from decaying vegetation) is a cancer risk if drank
Explain displacement reaction amongst halogens
More reactive halogen will displace a less reactive one from a compound
States at RTP of halogens
In order down grp: G G L S
Colour of halogens in water solution:
Cl2
Br2
I2
Pale green
Orange
Brown
Colour of halogen in organic solvent (cyclohexane) solution
Cl2
Br2
I2
Pale green
Orange
Violet
Why is cyclohexane added to halogen solution for identification/displacement reaction
Clearly differentiate between I2 and Br2 formation as both in water solution are similar in colour: orange vs brown
Difficult to tell apart depending on its conc
