Chemistry - Chemical Bonding Flashcards Part 1

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

When bonding occours, atoms tend to reach an electron arrangement with eight electrons in the outermost shell

Transition elements dont obey the octet rule and often have more or less than 8 electrons in the outer shell

Elements near helium tens to have 2 electrons in the outer shell

A charged atom/ group of atoms

Cations

Anions

The force of attraction between oppositly charged ions in a compound

Bohr diagrams, dot and cross diagrams

Crystal lattice structure

X-ray crystallography

Hardness- hard substances due to strong ionic bonds and crystal lattice structures.

Melting and boiling points- high melting and boiling points due to strong ionic bonds and crystal lattice structure.

Conduction of electricity.Dont condict electricity in solid state but do conduct electricity in the molten state or when dissolved in water as the ions are free to carry the charge.

Sc and Zn are not transition metals.Sc and Zinc have different properties to the other transition elements

An elements that forms at least one ion with a partially filled d sublevel.

Transition elements have varaible valency. Sc only forms SC3+ ions and zn only forms Zn 2+ ions

transition elements usually form colourful compounds, scandium and zinc only form white compounds.

Transition elements are widely used as catalysts. Sc and zn show little catalytic activity.

the number of atoms of different elements in which a certain element can combine with.

One which involves that sharing of electrons between atoms.

A group of atoms joined together. Its the smallest partical of an element or compound that can exist independently

Covalent compounds

The number of atoms of hydrogen or any other monovalent element with which each atom of the element combines

one pair of electrons are shared between two atoms

two pairs of electrons are shared between two atoms

three shared pairs of electrons

Aldehydes

A sigma bond is fored due the head-on overlap of two orbitals, (All single covalent bonds can be describes as a sigma bond)

Molecular orbital

A pi bond is formed due to sideways/ lateral overlap of P orbitals

There is less overlap between orbitals in a pi bond, therefore it is weaker than a sigma bond

1 sigma bond

1 sigma and 1 pi bond

1 sigma and two pi

Ionic

Contains a network of ions in the crystal

usually hard and brittle

high melting and boiling points

usually solid at room temperture

conduct electricty when dissolved in water or molten

Covalent

contain individual molecules

usually soft

usually have low melting and boiling points

usually liquid or gasses at room temperature

dont conduct electricity ( no ions present)

Valance shell electron pair repulsion theory states the shape of a molecule depends on the number of pairs of electrons in the valence shell of the central atom

electrons are negativily charged, the electron pairs repel eachother and arrange themselves in space to be as far apart as possible.

Both electrons come from the same atom

each electron comes from a different atom

Special type of covalent bond where one atom supplies both the electrons

Eg. NH4+

Tetrahedral

Trigonal planer

Linear

Pyramidial

V-shaped / bend

109.5

120

180

107

104.5

Pyramidial and v-shaped

The relative force of attractions two atoms in a molecule have for a shared pair of electrons in a covalent bond

Polarity of covalent bonds

perdict which compounds are ionic and which ones are covalent

the pair of electrons are shared equally between the two atos in the molecule

more attracted to one atom than another.

Delta δ

the bonding electrons aren't shared equally. There is a partial postive and partial negative charge on the molecule.

These partial charges are seperated by some distance

refers to a covalent bond where there is equal sharing of electrons

It cant be symmetrical

Water is v shaped, cant be symmetrical.

warer is a good solvent. most ionic substances and most polar covalent substances dissolve in water. Opposite charges are attracted towards eachother.

Ionic bonding

Polar Covalent bond

Non polar covalent bond

to show if a compund (usually a liquid)is polar.Water is polar. ( has tempoary postive charges associated) water will deflect when a postively or negativily charged rod comes near. The H postive will be attracted towards the negativily charged rod.Similarly, the O (negative) will be sttracted to th negativitly charged rod.

Cyclohexane is an organic compound that is non-polar (no deflection)

boing that takes place within a molecule

Ionic, Polar covalent, non polar covalent

Forces of attraction between molecules

van der waals forces, dipole-dipole forces, Hydrogen bonding

weak attractive forces between molecules resulting from the formation of tempoary dipoles

All non-polar molecules, Nobel gas atoms

Have low boiling points (often gasses at room temperture) Insoluble in water( they are non polar and dont form hydrogen bonds with water)

Very weak attractive force

the number of electrons present increases (bigger atomic number)

Number of tempoary dipoles formed increases.

The strenght of van der waals forces increases.

bigger the molecule/atom, higher the boiling point

Forces of attraction netween the negative pole of one molecule an the postive pole of another

all polar molecules

H2O,HF,NH3

Dipole dipole forces are stonger than van der waals forces.

substances with dipole dipole forced between their molecules have highter melting and boiling points.

Hydrogen bonds are particular types of dipole dipole attractions between moleules in which hydrogen atoms are bonded to nitogen, oxygen or fluorine

The hydeogen acts as a bridge between two electronegative atoms in seperate molecules. Flurinr, oxygen and nitrogen are very small electronegative elements. gives the molecules strong polarity

Strongest intermolecule force.

higher boiling points and melting point.

Gives increased solubility in water.

H2O has twice as many haygrogen bonds between its molecules (HF)

Greater electronegivity value, greater

dipole (more polar)(NH3)

Ensures water is liquid at room temp so life can exist on earth.

Synthetic clothing- bullet proof vests/protective clothing.

hydrogen bonds in wool help it absorb water. hydrogen bonds in water give it a high surface tension.

gives water a unusually high boiling point (ensures water is liquid at room temp)

Gives water a high water tension.

(water to flow against gravity in plants)

Ensures ice is less dense than water

(fish can survive in lakes in the winter)