Chapter 2 Flashcards
Elements
Consits of one type of atom only
Compunds
Made up of two or more different elements which are chemically bonded together -> properties of compound differ from properties of original elements + difficult to seperate
Mixtures
Made up of two or more elements or compunds that aren’t chemically bonded together -> properties of mixture: a mixture of the properties of seperate parts + easily seperated with pysical methods
Atomic structure
Central nucleus containing protons and neutrons surrounded by electrons in shells
Neutral atoms
No overall charge as number of protons is equal to number of electrons -> if some electrons are added or removed the atom becomes charged and is now an ion
Relative mass of proton
1
Relative mass of neutron
1
Relative mass of electron
Approx 0 -> 0.0005
Relative charge of proton
+1
Relative charge of neutron
0
Relative charge of electron
-1
Atomic number/ proton number
Number of protons in nucleus of atom -> in neutral atom this tells us the element
(Smaller number)
Mass number/nucleon number
Number of protons and neutrons in nucleus of atom
(Bigger number)
Isotopes
Different atoms of the same element that have the same number of protons but different number of neutrons
- Isotopes have the same chemical properties, as chemical properties depend on the number of electrons and isotopes have the same number of electrons/electronic configuration
Relative atomic mass of an element (Ar)
Average mass of all isotopes of the element
Electron shell rules
- Electrons always occupy shells (energy levels)
- Lowest shells always filled first -> shells closest to nucleus
- Certain capacity of electrons in each shell
1st shell
2 electrons
2nd and 3rd shell
8
Outer shell electrons
Control reactivity as they from bonds with other atoms to gain or loose enough electrons to achieve a full outer shell and become stable + unreative
Ions
Charged particles
Anions
Negative ions -> form when atoms gain electroms
Cations
Positive ions-> form when atoms loose electrons
Ionic bonding
Between metals and non-metals -> metal atom looses electrons to form a cation and a nonmetal gains these electrons to form an anion
- These oppositely charged ions are strongly attracted to each other by electrostatic attractions -> ionic bonding
Ionic compund properties
Always have gaint ionic structure -> regular arrangement of alternating positive and negative ions
- High melting/boiling points (low volatility) -> strong attractive forces between closely packed ions in giant ionic lattice (takes a lot of energy no break bonds)
- When solid -> can’t conduct electricty but do conduct when aqueous or molten -> ions are mobile and carry electric charge
Covalent bond
Pair of electrons shared between two atoms to a noble gas electron configuration
Covalent compund properties
- Low melting/boiling points (high volatility) -> intermolecular forces are weak
- Don’t conduct electricty -> don’t have ions, only uncharged molecules
The 3 types of giant covalent structures
Graphite
Diamond
Silicon
Graphite: description
- Black, shiny solid
- Each carbon atom forms 3 covalent bonds -> sheets of carbon atoms arranged in hexagons
Graphite: properties
- High melting/boiling point -> covalent bonds in hexagon need loads of energy to break
- Conducts electricity -> each carbon atom has one electron that’s delocalised which can move and carry electric charge: Graphite often used for electrodes
- No covalent bonds between layers so they can slide over eachother -> this makes graphite soft and slippery: graphite used as lubricant material
Diamond: description
- Transparent colourless crystals
- Each carbon atom forms four covalent bonds -> tetrahedral structure formed
Diamond: properties
- High melting/boiling point -> strong covalent bonds need lots of energy to break
- Very hard-> covalent bonds hold atoms in rigid lattice structure: Diamond used as cutting tool
- Doesn’t conduct electricity -> no free electrons
Silicon (IV): Description
- Similar giant tetrahedral lattice to diamond
- Silicon atoms positioned like carbon atoms in diamons, with an oxygen atom between each one
Silicon (IV): properties
- High melting/boiling point -> strong covalent bonds need loads of energy to break
- Hard -> covalent bonds hold atoms in rigid lattice structure
- Doesn’t conduct electricity -> no free electrons
Metallic bonding
Electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocolised electrons which holds atoms together in a regular structure
Physical properties of metallic bonding
- Good electrical conductivity: delocolised electrons are free to move and carry electric charge
- Ductility and malleability: positive ions in metal arranged regularly in layers, when force applied layers can slide over ecah other
Giant ionic lattice
Regular arrangement of alternating positive and negative ions
