LC CHEMISTRY- BONDING

compound

a substance that is made up of two or more different elements combined chemically together

state the "Octet Rule"

when bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost energy level

exceptions to octet rule

transition metals usually do not obey the octet rule

hydrogen lithium beryllium tend to achieve two electrons in the outermost energy level instead of eight

Elements in Group I of the Periodic Table..

+1 charge as they lose their 1 outermost electron

Elements in Group II of the Periodic Table..

+2 charge as they lose their 2 outermost electrons

Elements in Group III of the Periodic Table...

+3 charge as they lose their 3 outermost electrons

what are positive ions called

cations

Explain whats going on in the picture

to fulfil the octet rule sodium lost its valence electron in its outer shell. Sodium atom 2,8,1 to Sodium ion 2,8

Elements in Group VI of the Periodic Table..

-2 charge as they gain 2 electrons

Elements in Group VII of the Periodic Table..

-1 charge as they gain 1 electron

what are negative ions called

anions

describe whats going on in this picture

to fulfil the octet rule fluorine gained an electron in its outer shell. Fluorine atom 2,7 to Fluoride ion 2,8

ionic bond definition

the force of attraction between oppositely charged ions in a compound, always formed by the complete transfer of electrons from one atom to another

what do we use to show ionic bonding in a compound

dot and cross diagram

whats going on in the image here

the valence electron of na is transferring to the incomplete outer shell of cl, to fulfil octet rule

charges in a ionic compound are

always neutral

3 pieces of info on the Crystal Structure of Sodium Chloride

3d arrangement of ions called a crystal lattice

each sodium ion is surrounded by 6 chloride ions

each chloride ion is surrounded by 6 sodium ions

when writing the formula of any (transition complex etc) ionic compounds

-positive ion goes first

-find which group each of the elements are from

-work how much they lose or gain

-find lcm of the charges

-add necessary coefficients

complex ion definition

an ion made up of two or more different atoms

complex ion name: Hydroxide ion

write the....

Formula:

charge:

OH- 1-

complex ion name: Nitrate ion

Formula:

charge:

NO3- 1-

complex ion name: Hydrogencarbonate ion

Formula:

charge:

HCO3- 1-

complex ion name: Permanganate ion

Formula:

charge:

MnO4- -1

complex ion name: Carbonate ion

Formula:

charge:

CO3^2- 2-

complex ion name: Chromate ion

Formula:

charge:

CrO4^2- 2-

complex ion name: Dichromate ion

Formula:

charge:

Cr2O7^2- 2-

complex ion name: Sulphate ion

Formula:

charge:

SO4^2- 2-

complex ion name: Sulphite ion

Formula:

charge:

SO3^2- 2-

complex ion name: Thiosulphate ion

Formula:

charge:

S2O3 2-

complex ion name: Phosphate ion

Formula:

charge:

PO4^3- 3-

complex ion name: Ammonium ion

Formula:

charge:

NH4+ 1+

where are transition metals located

d block except scandium and zinc

why are the transition metals special what properties makes them special

used as catalysts

can make different ions with different charges e.g Mn(II) (IV) (VII)

can form coloured compounds

how to name the compounds given in formula form

look at the charges and work backwards

covalent bonding definition

when bonding electrons are being shared between atoms

molecule definition

a group of atoms joined together, it is the smallest particle of an element or compound that can independently exist

valency definition

the number of atoms of hydrogen which the element will combine with (outmost shell babes)

sigma bonding

head on overlap of atomic orbitals

pi bonding

sideways overlap of p orbitals

single bond

1 sigma bond

double bond

1 sigma bond 1 pi bond

triple bond

1 sigma bond and 2 pi bonds

ionic compound properties

hard and brittle

high melting and boiling point

solid at room temperature

conducts electricity when molten or dissolved in water

covalent compound properties

soft

low melting and boiling points

liquids, gases or soft solids at room temperature

do not conduct electricity

what theory do we use to predict the shapes of covalent molecules

valence shell electron pair repulsion theory

how do we carry out the theory

1 carry out dot and cross diagram of molecule in question

2 count how many bond pairs electrons are around the central atom of the molecule

3 count how many lone pairs electrons are around the central atom of the molecule

4 use number of bond and lone pair to find shape

shape: linear

no. bond pairs:

no lone pairs:

bond angles:

2 0 180

shape: V shaped

no. bond pairs:

no lone pairs:

bond angles:

2 2 104.5

shape: Triangular

no. bond pairs:

no lone pairs:

bond angles:

3 0 120

shape: Pyramidal

no. bond pairs:

no lone pairs:

bond angles:

3 1 107

shape: Tetrahedral

no. bond pairs:

no lone pairs:

bond angles:

4 0 109.5

Electronegativity

is the relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond

non polar covalent bond

atoms in molecule all equally shared

polar covalent bond

atoms in molecule not equally shared, one end is slightly positive and the other end is slightly negative

how to find electronegative of a molecule

1 find lectronegativity of the molecule

2 use pauling scale to determine electronegaitvy

nonpolar bond on pauling scale

0.0 - 0.4

polar bond on pauling scale

0.4-1.7

ionic bond on pauling scale

> 1.7

how do we prove water is polar

water is polar, by placing a charged plastic rod near a thin stream of water (from a burette, if the rod is positively charged, the water molecules will spin so that the negative end of the water molecule is facing the rod, causing an attraction (SAY THE OPPOSITE TOO)

Intramolecular Bonding DEFINITION

bonding that takes place within a molecule e.g covalent bonding

Intermolecular Forces/Bonding definition

forces of attraction that exist between molecules

Intermolecular Forces/Bonding 3 examples order in weakest to strongest

van der waals forces

dipole-dipole forces

hydrogen bonding

van der waals forces definition

these are weak attractive forces between molecules caused by temporary dipoles

van der waals forces explaination

-in non-polar molecules the constant movement of electrons can create a slight negative charge on one side and a slight positive charge on the other, this temporary dipole can induce a similar dipole in nearby molecules, leading to attraction between them

-get stronger for bigger molecules

-the stronger the vwf on molecule higher the boiling and metal point

dipole dipole forces definition

forces of attraction between the negative pole of one polar molecule and the positive pole of another polar molecule

dipole dipole forces explaination

stronger intermolecular forces that occur between non polar molecule

the more electronegative atom in a molecule gains a partial negative charge, while the less electronegative atom gains a partial positive charge. + on one molecule is attracted to the - on nearby molecule, creating a dipole dipole attraction often shown with a dotted line

Hydrogen Bonds definition

particular types of dipole dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine, hydrogen atom carries a partial positive charge and is attracted to the

electronegative atom (n, o or f) in another molecule

Hydrogen Bonds explaintion

hydrogen bonding is the strongest form of intermolecular force because of the big electronegativity

difference between the atoms

intermolecular bonding is...

much weaker than covalent bonds

how to answer exam q's with this

when given list of compounds and boiling

find which intermolecular forces they are

non-polar molecule → Van der Waals.

Polar molecule, but no H bonded to N, O, or F?→ Dipole-Dipole.

Polar molecule, with H bonded to N, O, or F? → Hydrogen Bonding.