C2.2-2.3 Flashcards
Physical property
Characteristic that cant be observed/measured
Physical properties of metals (left side)
- shiny
- high melting/boiling point
- solid at room temp
- malleable (bend without shattering) when solid
- ductile (can be pulled into wires) when solid
- good thermal/electrical conductors
Physical properties of non-metals (right side)
- dull
- low melting/boiling temps
- half solid, half gas at room temp
- brittle (shatter when hammered) when solid
- non-ductile (snap when pulled) when solid
- poor thermal/electrical conductors (insulators)
Chemical property
Characteristic of substance that can only be determined by studying its chemical reactions
Chemical properties of metals
- lost electrons to form positive ions
- don’t react with each other (mix to form alloys)
- react with oxygen to produce metal oxides which dissolved in water to produce alkaline solutions
chemical properties of non-metals
- gain electrons to form negative ions
- react with each other to produce compounds that consist of molecules
- react with oxygen to produce non-metal oxides which dissolve in water to produce acidic solutions
How do ionic compounds form?
A metal reacts with a non-metal
Electrons transferred from metal atoms to non-metal atoms so both more stable
- metals become positive ions
- non-metals become negative ions
Structure of ionic compound
contain positive & negative ions arranged in a regular way
= giant ionic lattice
Bonding of ionic compounds
- ions held in place by ionic bonds, act in all directions
Ionic bonds = strong electrostatic forces of attraction between oppositely charged ions
Covalent bonds
Shared pair of electrons
Between 2 non-metal atoms when atoms get close enough to share electrons in outer shells = complete outer shells = stable
Simple molecules
Particle in which a few non-metal atoms are joined to each other by covalent bonds
(Hydrogen, oxygen, water, carbon dioxide)
Structure & bonding of simple molecules
Covalent bonds = strong electrostatic forces of attraction between nucleus of each bonded atom & shared electrons
Weak intermolecular forces between molecules
Giant covalent structure
Consists of many non-metal atoms joined by covalent bonds
& arranged in repeating regular pattern = giant lattice
Example of a giant covalent structure
Diamond (form of carbon)
= carbon atoms joined to 4 other carbon atoms by covalent bonds
Chemical formula of giant molecules (giant covalent structures) & why
Too many atoms
Use empirical formula
Monomers
Simple molecules
= consist of few non-metal atoms joined to each other by covalent bonds
Bonding of polymers
- covalent bonds between individual polymer molecules
- weak intermolecular forces between polymer molecules
Types of polymer
- thermosoftening polymer: polymer chains relatively easy to separate
Thermosetting polymer: chains joined tougher by strong covalent bonds = cross linking, hard to separate
Structure of metals
Atoms packed together in regular way
= forms giant metallic lattice
(Solid state at room temp, except mercury)
Inner structure of metals which causes metallic bonds
- Electrons leave outer shells of metal atoms
- forming a sea of delocalised electrons around positively charged metal ions
- delocalised electrons = free to move through structure of metal
Metallic bonds
Strong electrostatic forces of attraction
between delocalised electrons & closely packed, positively charged metal ions
How did Mendeleev’s periodic table differ from the modern-day one
- had no noble gases (group 0)
- has no transition elements
- had gaps (left for elements to be discovered)
- was ordered by atomic mass but now ordered by atomic number
- didn’t have atomic number
- swapped iodine & tellurium to reflect chemical properties
What determines the chemical properties of an element
electronic structure of an element
Group 1 properties
- metals
- very unreactive
- electronic structure ends in 1
- forms +1 ion
Group 2 properties
- metal
- reactive
- electronic structure ends in 2
- forms +2 ion
Group 7 properties
- non-metal
- very reactive
- electronic structure ends in 7
- forms -1 ion
Group 0 properties
- non-metal
- very unreactive
- full outer shell (electronic structure ends in 8)
- doesn’t form ions (don’t react)
Why did Mendeleev not think argon and helium were elements at first
- both gases are inert (very unreactive, unable to form compounds)
- he though elements should be able to react with other elements
Who discovered the elements in group 0 and when
Ramsay
from 1894-1898
Why can carbon form many different compounds
In group 4 = 4 electrons in outer shell = can form 4 covalent bonds
Allotropes
Different forms of an element in the same state but with different atomic arrangements
Allotropes of carbon
- diamond
- graphite
- graphene
- fullerenes (large family) : nanotube, buckyball
Why do all allotropes have different properties even though they are all formed from carbon
Different structure & bonding
Diamond properties
- transparent
- very hard
- very high melting point
- doesn’t conduct electricity (insulator)
Diamond structure & bonding
Giant covalent structure
- each carbon atom covalently bonded to 4 other carbon atoms
Covalent bonds = strong
why does diamond have a very high melting point & is very hard
- has lots of strong covalent bonds, difficult to break
why doesn’t diamond conduct electricity
- all outer shell electrons in its atoms are shared when covalent bonds are formed
= no delocalised electrons
Graphite properties
- soft
- grey-black
- conducts electricity
- very high melting point
- slippery
Why does graphite conduct electricity
1 electron in outer shell of each atom not involved in bonding (only bonds to 3 electrons)
= delocalised electrons free to move through structure
Why does graphite have a very high melting point
- layered structure
- atoms in each layer form interlocking hexagons like knots
- many strong covalent bonds in layers
Why is graphite slippery
weak forces between each layer = layers slide over each other easily
(Graphite tip on pencil)
Graphite structure & bonding
Giant covalent structure
- each carbon atom covalently bonded to just 3 other carbon atoms
