bonding Flashcards by Joshy :)

what is structure of ions

A regular lattice of alternating positive and negative ions

lattice held by electrostatic forces

Crystal structure

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properties of lattice and why (5)

very high melting point due to strong electrostatic attraction between oppositely charged ions therefore requires a lot of energyy to break

Generally soluble in H₂O- as water is very polar so it can disrupt the electroctatic attractions between the ions and break them up

insulator when solid- ions are fixed in position so cannot carry a charge

Electrical conductors when molten/ dissolved- as ions are free to move so able to carry a charge

Brittle - when moved. Ions no longer have an alternating arrangement which means they repel each other and the lattice breaks

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what is a covalent bond

shared pair of elctrons with opposite spins, and one electron is donated by each atom

(multiple eg double bond when 2 pairs of e- shared etc)

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what does a covalent bind form between

forms between elements that have high electronegativty values (non-metals)

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what forces are involved in a covalent bond

highly negative/ high e- density where elctrons shared

And the very strong attraction between the electrons and positive nuclei

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types of covalent structures

molecular:

simple covalent i.e CH_4,H₂O

macromolecular:

giant covalent i.e. diamond and graphite

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what is a coordinate bond (dative)

a covalent bond formed when both electrons are donated by the same atom

once formed, acts in the same way as a covalent bond

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how is ice formed

H₂O is a covalent bonded molecule therefore hydrogen bonding exists between molecules

between 0ºC - 100ºC, bonds hold molecules close to each other but allow free movement

Below 0ºC, molecules have less energy so hydrogen bonding fix molecules in position

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what structure does ice have

Ice has 3d hexagonal crystal structure

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how are properties of ice affected by structure (2)

ice floats: spaces creates b/c of 3D hexagonal crystal structure

spaces created between spaces

spaces are caused to expand and become less dense

relatively high mp: strong hydrogen bonding between the molecules

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what is bonds between iodine

is a covalently bonded molecule (covalent bond is very strong)

weak induced dipole/ van der waal’s forces between molecules which gives crystal structure

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iodine properties (5)

shiny grey at room temperature

Low melting point- weak vane dear wall’s forces are very easily broken but I₂ molecules stay intact

Sublime(s=>g) when heated the grey solid turns into purple gas

Slightly soluble in H₂O- b/c I₂ is non-polar

Only in potassium iodide solution and iodide ions allows it to dissolve

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structure of diamond

Each C atom form 4 single covalent bonds with 4 other C atoms

Tetrahedral arrangement (109.5)

Forms a 3d lattice of solid carbon

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properties of diamond

Very hard: Due to the structure of double carbon covalent bonds

Very high melting point: Due to strong double carbon bonds, require a a lot of energy to break

Electrical insulation: All electrons involved on bonding/ no delocalised e-

Insoluble: Due to strong double carbon bonds

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structure of graphite

Each carbon forms 3 single covalent nods with 3 other carbons

4^th is delocalised

Trigonometry planar shape (120)

Forms a 2d hexagonal structure with delocalise delctrons

Weak van dear ewaals forces between the layers

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properties of graphite

soft: due to weak van dear wall’s forces therefore layers can slide over each other

Very high melting point- strong double carbon covalent blonds therefore requires a lot of energy to break

Electrical conductor- delocalised elctrons are able to carry a current

Insoluble due to strong strong double cc bonds

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what is a metallic bond

occurs between pure metals and alloys

A regular lattice of cations surrounded by a sea of delocalised electrons

Has non-directional electrostatic attractions between these

forms a metallic crystal structure

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properties of metallic crystal structure

High melting points: due to strong electrotatics attractions

Conducts electricty: delocalised delctrons free to carry a charge

Conducts heat: delocalised elcetrons quickly transfer energy

Malleable/ductile: delocalised elctrons able to move with the ions when moved so don’t remove non-directional electrostatic attractions hence able to change shape.

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what are trends in mp in metallic crystal structure

variations:

increases across a period due to increasing charge on ions

Decreases down a group due to increased shielding

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what is VESPR

Valence shell electron pair repulsion

Used to determine the shapes of covalent molecules with 3 or more atoms

Molecules can contain both:

bonding pairs (covalent, coordinate, double, triple) and Lone pairs (unbounded electron pairs on the central atom)

repulsion: electron pairs repel each other and settle in a position to minimise repulsion i.e maximisawe bond angle

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list of most repulsive to least

lone pair-lone pair

lone pair- bonding pair

bonding pair-bonding pair

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3D structure notation:

methane

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what shape does these electron pairs make:

2 bonding pairs and no lone pairs

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linear

what shape does these electron pairs make:

2 bonding pairs and 2 lone pairs

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bent

what shape does these electron pairs make: 3 bonding pairs and no lone pairs

trigonal planar

what shape does these electron pairs make: 3 bonding pairs and 1 lone pairs

trigonal planar

what shape does these electron pairs make: 4 bonding pairs and no lone pairs

tetrahedral

what shape does these electron pairs make: 5 bonding pairs and no lone pairs

trigonal bipyramidal

what shape does these electron pairs make: 6 bonding pairs and no lone pairs

octrahedral

what shape does these electron pairs make: 4 bonding pairs and 2 lone pairs

square planar

how to find shape of unknowns

1) Decide central atom 2) Count valence e- 3) Count e- used by outer atoms to make bonds with central 4) Sum of 2) and 3) and divide by 2 = 2 VSEP 5) Use no. of BP and LP to predict geometry

how to find bond angles of unknowns in larger molecules eg ethanol eg hydrazine eg glucose

split molecule into smaller version as the overall shape is going to be combined

find bonding angles of : ethanol (C₂H₅OH)

1) Find the h-c-h bond angle where 4 BP(+0LP) around central c atom Tetrahedral therefore 109.5 2) Find the c-o-h bond angle where 2 BP +2 LP around the central o atom Bent therefore 104.5

find bond angles of: hydrazine (N₂H₄)

1) Find the h-n-h bond angle wher 3 BP + 1LP around the central n atom Trigonal pyramidal therefore 107 (happens twice)

find bond angles in: glucose (C₆H₁₂O₆)

1) C-c-c bond angle is 109.5 3 BP around c atom trigonal planar 2) C-o-c bond angle =104.5

what is electronegativity

the power of an atom to attract a bonding pair of electrons

trends on periodic table with electronegativity

- Where the least negativity is low effective charge = on nucleus and high shielding - where the most electronegativity is high effective charge= on nucleus and low shielding Group 8 is discounted b/c full outer shell therefore not reactive

how does elctronegativity affect bonding in

what: Electrons are shared equally why: electronegativity is the same properties: Non-polar, No di-pole, 2 of the same element eg. H_2,N_2, F₂

how does electronegativity affect a) covalent b) ionic bonding

Covalent- a difference in electronegativity causes pairs of electrons in a bond to be shared unequally Ionic- difference in elctronegativity so big so elctrons are transferred

how does electronegativty affect bonding in

what: Electrons shared unequally why: Y has a greater electronegativity so BP of e- drawn towards it properties: Polar, Dipole, 2 elements that are different

how does electronegativity affect in

what: electrons shared unequally in favour of X why: Large difference in electronegativity Specifically: h-f, h-o, h-n properties: Polar, Dipole, Hydrogen bonding

what are induced dipole forces

Occur between all molecules Weakest intermolecular forces Strength varies- increased with increasing Mr (more electrons involved)

examples of induced dipole forces (3)

eg. monatomic elements, cannot be polar because no elctronegativity eg. Diatomic elements, have no permanent dipole because atoms have same elctronegativity Eg larger non-polar molecules, moloceules are symmetrical therefore. No obvious poles (f+ f-) All these examples show increasing strength of imf with increased mr Therefore show increased mp/gp as more energy needed to break imf

what are permanent dipole forces

occur between polar molecules Stronger that induced dipole forces but weaker than h bonding Causes these compounds to have a higher than expected mp/bp