2D- bonding and structure

melting point of a giant ionic lattice

high

can a giant ionic lattice conduct electricity?

no when solid, yes when liquid or in solution

melting point of a simple molecule

low

bonding in a simple molecule

covalent

can a simple molecule conduct electricity?

no

melting point of a giant metallic lattice

high

can a giant metallic lattice conduct electricity?

yes when in solid and even better as a liquid

melting point of a giant covalent lattice

high

can a giant covalent lattice conduct electricity?

no

definition of ionic bonding

electrostatic attraction between positive and negative ions

types of bonding

ionic, covalent, metallic

definition of covalent bonding

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

what is a giant structure

a 3D continuous structure

definition of metallic bonding

the strong electrostatic attraction between positive metal ions and delocalised electrons

types of paired electrons

bonding pair and lone pair

a shared pair of electrons is called…

a bonding pair

a pair of electrons in the outer shell not used in bonding is called

a lone pair

what is a dative covalent bond

a shared pair of electrons in which the bonded pair has been donated by one of the bonding atoms only

what is the name for a shared pair of electrons in which the bonded pair has been donated by one of the bonding atoms only

a dative covalent bond

how do you show ‘extra’ electrons in polyatomic ion dot and cross diagrams

using a different symbol

why are giant ionic lattices brittle

a layer of ions moving over the others a little causes the negative and positive ions of two layers to match up. this makes the layers repel each other and the layers break apart

ionic bond definition

the electrostatic force which holds two oppositely charged ions together

simple molecular structure definition

a small unit containing a definite number of atoms with a definite molecular formula

giant covalent structure definition

billions of atoms held together with electrostatic attractions to form a network of strong covalent bonds

key phrase when talking about electrical conductivity

mobile charge carriers

how many bonds and which type does each carbon atom have in diamond

4 covalent bonds

how many bonds and which type does each carbon atom have in graphite

3 covalent bonds

can diamond conduct electricity

no

can graphite conduct electricity

yes- only three bonds, so has delocalised electrons to be mobile charge carriers

is graphite hard or weak and explanation

weak- strong covalent bonds within layer, weak intermolecular forces between layers, meaning they can slide over each other

is diamond hard or weak and explanation

hard- strong covalent bonds between carbon atoms, tetrahedral structure spreads forces throughout

uses of graphene

solar cells, LEDs, smartphone screens, filtration, printer powder

shape of rings in graphene

hexagonal

why are metals insoluble in water/ non-polar solvents?

the strong electrostatic attractions between the cations and the delocalised electrons are maintained as there isn’t the large quantity of energy needed to break them available

why are some metals better conductors of electricity?

they have more delocalised electrons per metal ion to act as mobile charge carriers

malleable definition

easily bent into different shapes

ductile definition

can be drawn out into wires

what is it called when a substance can be drawn out into wires

ductile

how are metals malleable and ductile

the layers are able to easily slide over each other

what are graphite and diamond of carbon?

allotropes

what are alloys

mixtures of metals

what are common alloys in everyday life

stainless steel, brass

which metals are present in the alloy stainless steal

chromium and iron

which metals are present in the alloy brass

copper and zinc

how does an alloy make a metal harder

the different sized ions of the different elements distorts the neat layers. this means the layers cannot slide over each other as nicely, and so the metal is harder

VSEPR theory states:

• electron pairs repel each other as much as possible; they will adopt positions where they are separated by the largest possible angle

• lone pairs repel more strongly than bonded pairs, so the repulsion between lone pair-lone pair> lone pair-bonded pair> bonded pair-bonded pair

how are multiple bonds count in VSEPR theory

same as a single bond, one region of electron density

bond angle and shape when a molecule has 2 bonding pairs and 0 lone pairs

180’, linear

bond angle and shape when a molecule has 3 bonding pairs and 0 lone pairs

120’, trigonal planar

bond angle and shape when a molecule has 4 bonding pairs and 0 lone pairs

109.5’, tetrahedral

what is the bond angle of a tetrahedral shape

109.5’

bond angle and shape of a molecule with 6 bonding pairs and 0 lone pairs

90’, octahedral

bond angle and shape of a molecule with 3 bonding pairs and 1 lone pair

107, trigonal pyramidal

bond angle and shape of a molecule with 2 bonding pairs and 2 lone pairs

104.5’, non-linear

bond angle of a non-linear shape

104.5’

bond angle of a trigonal pyramidal shape

107’

why is a bond angle less when a lone pair is present

each pair try to repel each other as far apart as possible, repulsion between lone pair-bonded pair> bonded pair-bonded pair, the bond angle is slightly reduced

define electronegativity

the ability of an atom to attract the bonding electrons in a covalent bond

how is electronegativity measured

Pauling scale

what are the four most electronegative elements

fluorine, oxygen, nitrogen, chlorine

what is the Pauling electronegativity value of fluorine

4.0

what is the Pauling electronegativity value of oxygen

3.5

what is the Pauling electronegativity value of nitrogen

3.0

what is the Pauling electronegativity value of chlorine

3.0

what is the relationship between Pauling value size and degree of electronegativity

the higher the Pauling value, the bigger the electronegativity

permanent dipole definition

a small charge different that does not change across a bond, with partial charges on the bonded atoms (the result of the bonded atoms having different electronegativities)

what symbols are used to represent partial charges in a bond with a permanent dipole

delta positive and negative

why are carbon-hydrogen bonds considered to be a non-polar bond

they have very similar electronegativity values

polar covalent bond definition

a bond with a permanent dipole, having positive and negative partial charges on the bonded atoms

polar molecule definition

a molecule with an overall dipole, having taken in to account any dipoles across bonds and the shape of the molecule

criteria needed to be a polar molecule

• the molecule must contain polar bonds

• the charges on the molecule must not be symmetrical- the central atoms is not entirely surrounded by atoms of equal electronegativities and/or has lone pairs

which structure would you find intermolecular forces

simple covalent lattices

types of intermolecular forces

induced dipole-dipole interactions/London Forces, permanent dipole-dipole interactions, hydrogen bonds

how do London Forces arise

electrons are constantly moving, at any instant the distribution may not be symmetrical, this results in an instantaneous temporary dipole, this dipole induces dipoles in neighbouring molecules and leads to an attraction between neighbouring charges in the dipoles, these attractions between molecules are known as London Forces

what molecules have London Forces

all of them, only intermolecular force that acts between non-polar molecules

what affects the strength of London Forces

electrons, contact area

how do electrons affect the strength of London Forces

the more electrons there are in the molecule, the greater the fluctuations in the electron cloud, and the stronger the instantaneous dipole -induced dipole forces

how does contact area affect the strength of London Forces

for molecules with the same number of electrons, the greater the contact area between the molecules the stronger the induces dipoles that develop, long thin molecules can line up beside each other more closely than short spherical ones, hence unbranched molecules have stronger London Forces than branched molecules

are London Forces and permanent dipole-dipole forces mutually exclusive

no, permanent dipole-dipole forces occur in addition to induced dipole-dipole forces, making those molecules tend to have higher boiling points

are permanent dipole-dipole forces stronger than London Forces

yes when there are similar numbers of electrons

which is the strongest intermolecular force

hydrogen bonds

hydrogen bond definition

a strong dipole-dipole attraction between an electron-deficient (delta+) hydrogen atom of NH, OH or HF on one molecule and a lone pair of electrons on a highly electronegative atom (N,O or F) on a different molecule

rules for drawing hydrogen bonds

• drawn as a series of dashes between the lone pair and hydrogen pair

• the lone pair on O/N/F must be shows

• partial charges must be shown

• the 2 bonds/hydrogen bonds either side of the H must be in line

polar molecules have which intermolecular forces

London Forces and either permanent dipole-dipole interactions or hydrogen bonds

what causes the anomalous properties in water

it can form 4 hydrogen bonds per molecule

what are the anomalous properties of water

• high melting and boiling points than expected for a molecule of its size

• ice is less dense than water due its open structure

why does ice have a lower density than water

when it freezes each water molecule forms 4 hydrogen bonds with other water molecules, forces molecules to spread out more than in liquid water, so there are fewer molecules per given volume