ionic compounds, covalent bonding & simple molecular substances

structure of ionic compound

giant ionic lattice

What is a giant ionic lattice

positive ion is surrounded by negative ion

what is a regular lattice structure

very strong electrostatic forces of attraction between opposite charge ions in all direction

what is sodium chloride

salt, has one giant ionic lattice, na+ and cl- ions held together in a regular lattice

properties of ionic compounds

high melt and boil points cus strong bonds between ions, when solid they cant conduct, when melted ions move free and carry charge, some dissolve in water

formula of ionic compound if given dot and cross diagram

count how many atoms of each element

formula for ionic compound if given 3d diagram of ionic lattice

work out what ions are in compound, balance charges of ions so overall charge of compound is 0

covalent bonds

share electrons

what happens when non metal atoms bond together

share pairs of different electron make covalent bonds, positive nuclei bond to atoms to share a pair of electrons, electrostatic forces, strong bond

different ways of drawing covalent bonds

dot and cross diagram, formula, 3D model

Dot and cross diagram

electrons drawn in overlap between outer shells of two atoms are shared between those atoms

formula

shows bonds as lines between atoms

3d model

scaled representation of covalent bonds

examples of simple molecular substances

hydrogen, chlorine, hydrogen chloride, methane, ammonia, water, nitrogen, oxygen

hydrogen- H2

atom has 1 electron, needs 1 more to complete shell, forms covalent bond with other hydrogen atom or elements

chlorine- Cl2

2 chlorine atoms share pair of electron and form a single covalent bond

oxygen- O2

needs 2 more electrons, oxygen atoms share 2 pairs of electron, makes double covalent bond

nitrogen- N2

needs 3 more electrons, 2 nitrogen atoms share 3 pairs of electron, makes triple bond

methane- CH4

carbon has 4 outer electrons, forms 4 covalent bonds with hydrogen

water- H2O

oxygen shares a pair of electron with 2 hydrogen atom, forms 2 single covalent bond

hydrogen chloride- HCl

both atoms need 1 more electron to complete outer shell

what are atoms within molecules held by

very strong covalent bonds means forces of attraction between molecules is weak

what do you need to do to melt or boil simple molecular compounds

break feeble intermolecular forces and not bonds

at room temp what state are molecular forces

liquid or gas

what happens when molecules get bigger

strength of intermolecular forces increases, so more energy need to break them, melt and boil point increases

why cant molecular compounds conduct electricity

not charged, no free electrons or ions