chemical bonding

compound

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

compound with -ide

compound with -ate

ide: contains two elements

ate: contains two or three elemts (one is an oxygen)

molecule

group of atoms joined together

def: Octet rule

when bonding occurs atoms tend to reach the electron arrangement with eight electron in their outermost energy level.

exceptions to the octet rule

• transition metals

• Hydrogen, Lithium and Beryllium (achieve two electrons in their energy level)

def: Ionic bonding

the force of attraction between oppositely charged ions in a compound

ionic bonding

transfer of electrons

between metals and nonmetals

def: ion

charged atom/group of atoms

about an ion

• an atom becomes an ion when it gains or loses electrons

• square brackets represent ions

elements in group 1,2 and 3: positive cations

Elements in Group	Lose	charge
1  (I)	1 electron	1+
2 (II)	2 electrons	2+
3 (III)	3 electrons	3+

elements in group 6 and 7: negative anions

Elements in group	gain	charge
6 (VI)	2 electrons	2-
7(VII)	1 electron	1-

formulas of ionic compounds

between non metals and metals

Group 1 and 2: metals - lose electrons

Group 6 and 7: non metals - gain electrons

complex ions

• separate flashcards

metals are always__

non metals are always ___

metals - positive

non metals negative

when writing ionic compunds

• Positive ion (metal) goes first

• Negative ion (non-metal) goes second

• Multiply by the smallest possible integer to make the + and - the same 

• If the ion is complex put it inside a bracket and put the subscript outside the bracket 

crystal lattice structure

Three-dimensional arrangement of ions in a crystal.

• Each single unit cell repeats itself in all directions to build up a crystal.

valency

the number of atoms of hydrogen that the element will combine with. 

def: transition metal

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

Properties of Transition metals ***(applies to all transition metals except for scandium and zinc)

• Have variable valency

• Form coloured compounds

• Widely used as catalysts

Covalent bonding

involves the sharing of electrons

overlap of orbitals

between nonmetals and nonmetals

single bond

double bond

triple bond

Single Bond- 2 electrons

Double Bond- 4 electrons

Triple Bond-6 electrons 

molecule

group of atoms joined together

def: sigma bond

formed by the head on overlap of 2 circle or px orbitals

def: pi bond

formed by the sideways overlap of two pz or py orbitals

single bond:

double bond:

triple bond:

single bond: sigma bond

double bond: one sigma one pi bond

triple bond: one sigma and two pi bonds

properties of ionic and covalent bonds

	Ionic	Covalent
1.	Contain a network of ions in crystals	Contains individual molecules
2.	Usually hard and brittle	Usually soft
3.	Have high melting and boiling points	Have low melting and boiling points
4.	Solid at room temperature	Usually liquids, gases or soft solids at room temperature
5.	Conduct electricity in molten state when dissolves in water	Do not conduct electricity.

shapes of covalent molecules

tetrahedron

pyramidal

triagonal planar

v shapes/angular

linear

tetrahedron

bonding pairs: 4

lone pair: 0

bond angle: 109.5

no. of atoms: 5

pyramidal

bonding pairs: 3

lone pair: 1

bond angle: 17

no. of atoms: 4

triagonal planar

bonding pairs: 3

lone pairs:0

angles: 120

no. of atoms: 4

V shapes/ angular

bonding pairs: 2

lone pairs: 2

bond angle: 104.5

no. of atoms: 3

Linear

bonding pairs:2

lone pair: 0

bond angle: 180

no. of atoms: 3

exceptions

BF₃ - Trigonal planar

BeCl - Linear

exceptions regarding shapes of molecules

linear

tetrahedral

trigonal planar

(all non polar)

def: electronegativity

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

electronegativity in covalent bonds

one atom in a molecule has a greater pull - this means its more electronegative

non polar covalent

atoms in a molecule that share electrons equally

polar covalent

the atoms in a molecule that have an uneven distributin of electrons

use of electronegativity

• to predict the polarity of covalent bonds

• to predict which compounds are ionic and covalent

electronegativity values

Value	Bonding
0 - 0.4	Non polar covalent
0.4 - 1.7	Polar covalent
Over 1.7	Ionic bonding
Equal or under 1.7	Covalent bonding

intramolecular bonding

bonding that takes place within a molecule

intermolecular forces

forces of attraction that exist between molecules

def: Van der Waals

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

• between non polar molecules

the bigger and stronger the van der waal force

bigger - van der waal force gets bigger

stronger - higher boiling and melting point

def: dipole - dipole forces

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

• molecules with a permanent dipole

def: Hydrogen bonding

particular type of dipole-dipole bonding where the hydrogen atoms are bonded to Nitrogen, oxygen and Flourine.

• hydrogen carries a partial positive charge and is attracted to the electrnegative atom (N,O or F)

how to tell which force it is

Van der Waals	Non- polar molecules (noble gases, hydrocarbons)
Dipole-Dipole	Polar molecules
Hydrogen Bonding	When hydrogen is bonded with an electronegative atom (N,O and F)