Topic 1 - Key concepts in Chemistry Flashcards
23
Na
11
what is the top number
The relative atomic mass
23
Na
11
what is the bottom number
the atomic number
What is the relative atomic mass?
The total number of protons and neutrons
What is the atomic number
The number of protons (therefore the number of electrons)
What are isotopes?
an element which can have different numbers of neutrons
Proton
Mass of 1
positive charge
electron
very small mass
negative charge
neutron
mass of 1
no charge
The equation for Relative atomic mass
(rm x ra) + another dpending on how many / total abundance
Electron configuration rules
The first shell can only contain 2 electrons
the shells after hold 8
fill from in to out
What do atoms think when they dont have a full outer shell?
They wanna be stable, so they want to chemically react.
what are bonds?
forces of attraction that holds the atoms together
what type of atom changes name when turning into ion? what ending?
Non- metals and ends with ide or ate
What is an ion?
an atom or group of atoms that have lost / gained electrons resulting in a net charge
What are cations
Metals will always loose electrons and become postively cvharged.
Wat are anions
A
Non metals will gain electrons and become negatively charg
Ionic bonding between
metal and non metal
Ionic Bonding vs Covalent Bonding
Covalent bonding between 2 non metals.
ionic is a metal and a non metal
What are ionic compounds
ionic compounds contain one or more cation paired with one or more anion
they are formed by the loss or gain of electrons
they are held together by strong electrostatic forces of attraction between opposely charges ions
Why do ions form lattice structures?
They are because the stong electrostatic forces let “billions” of ions to be packes together in this regular repeating structure
What does the ending ide or ate mean in a ion?
it shows the ion has oxygen and another element in it
Why do ionic compounds have such a high melting and boilig point?
there is strong electrostatic forces that hold them together, it takes alot of energy to break these bonds
When do ionic compounds conduct electricity?
WHen they are molten or dissolved in water
its the chargged ions that carry the current, so they need to be free to conduct
What 2 conditions must be met for a thing to conduct electricity?
It must contain charged particles
these particles must be free to move
What are simple molecular substances ?
molecules held together by covalent bonds
When are covalent bonds usually formed?
between 2 non metals sharing pairs of electrons
They are strong
How are the atoms in molecules held together?
the strong electrostatic forces of attraction between the nuclei and the shared electrons
how are ionic compounds electrically neutral?
the 2 components have balancing positive charge and negative charge
Why do ionic copounds only conduct when molten or in aqueous solution?
The particles to be free to carry the current for it is the charged ions that actually carry it.
What is the law of conservation of mass?
In a chemical reaction, mass is always conserved in a closed system
Concentration =
mass of solute in g/
volume of solution in dm3
Why may mass appear to be lost in an open system?
the products may be gases released into the air
What is the Empirical formula?
the simplest whole number ratio of atoms or ions of each element in a substence
As well as Empirical formula, what do simple molecules have?
A molecular formula
Molecular formula
the amount of atoms of each element actually in that molecule
What is the symbol for relative formula mass?
Mr
What is the symbol for relative atomic mass?
Ar
How do you calculate Mr
Add the Ars in the compound
How to calculate Empirical formula
Mass / Mr
then divide by smallest number
What is a Mole
an amount fo particles
1 mole = Mr or Ar of a molecule
What is the formula triangle envolving mass, Mr and moles
Mass
Mr I Moles
What is avogadro’s constant?
6.02 x 10^23
How do you turn cm3 into dm3
/1000
Diamond structure
4 Covalent bonds per atom
Forms tetrahedons
Properties of diamond
very high melting and boiling points
Does not conduct electricity
Very hard
Insoluble in water
Giant covalent structures properties
Strong covalent bonds between atoms
High melting and boiling points
usually poor conductors of electricity
usually solid at RT
Very poor solubility in water
Allotrope
Different structural form of the same element
Why does diamond have high melting and boiling points?
Strong covalent bonds take alot of energy to overcome
Intermolecular forces
Why is diamond hard?
It is resistant to scratching cutting or denting because it is bonded with 4 covalent bonda witha tetralhedral structure
Drill tips
Why is diamond insoluble?
due to very strong covalent bonda between the atoms
Structure of Graphite
3 covalent bonds per carbon atom
Layers of hexagons
Weak intermolecular forced between layes
crystalline structure
One free electron per carbon aton
1.
Properties of graphite
High melting ang boiling points
Conducts electricity
Solid at room temp
Soft
Insoluble in water
Metallic Bonding
Metals in solids have their outershells de-localised. The sharing of these de-localised electrons creatre strong metallic bonds
What is the formula for Ammonia?
NH₃
What is the formual for Ammonium Ion
NH₄⁺
What is the formula for Nitrate ion?
NO₃⁻
What is the formula for sulfate ions?
SO₄²⁻
WHat is the formula for cabonate ions?
CO₃²⁻
What does the ball on fire hazard mean?
Oxidising
Provides oxygen which allows other materials to burn more fiercely
E.g Liquid oxygen
What does the exclamation mark hazard mean?
Harmful
Can cuase irritation, reddening or blistering of the skin
E.g Bleach
What does the tree and dead fish hazard mean?
Environmental hazard
harmful to organisms and to the environment
E.g Mercury
What does the Fire on a line Hazard mean?
Highly Flammible
Catches fire easily
E.g Petrol
What does the skull hazard mean?
Toxic
Can cause death if consumed, absorbed, or inhailed.
E.g Hydrogen Cyanide
What is the test tube and hand hazard?
Corrosive
Destroys materials, including living tissues (skin)
E.g Concentrated sulfuric acid
What was John Dalton’s theory of atoms?
Solid spheres, Different spheres made up different elements
19th century
What was J.J Thompsons theory of the atom?
The Plum Pudding
He mesured charge and mass and concluded that an atom must contain smaller, negatively charged particles (electrons)
1897
What did the Plum pudding model look like?
Spherical positively charged pudding with smaller electrons in it
What was the gold foil experement?
Ernest rutherford and his students, Hans Geiger and Ernest marden.
Fired positively charged alpha particles at a thin sheet of gold
1909
How did the gold foil experement disprove the plum pudding model?
Based on the plum pudding model, the alpha particles would pass right through the sheet or be slightly deflected at most.
Some were delflected more than expected.
How did the Nuclear atom model form from the gold foil experement?
Rutherford theorised that there was a tiny, positively charged nucleus at the centre. This would reason the alpha particles were deflected more than expected.
How did Neils Bohr refign the theory of the atom?
Bohr suggested that electrons are in fixed shells or orbits, with fixed energy levels.
How are ionic bonds held together?
They are strongly atttracted by electrostatic forces in the oppositely charges ions
Ionic bonds vs Ionic compounds
Ionic compounds are the entire thing, molecules
Ionic bonds are the forces that hold them together
What structure do ionic compounds have?
Regular lattice / Giant ionic lattice
molecules
Groups of atoms
What size are simple molecules?
10x-10 m
How are simple molecules held together?
The atoms within are held together by very strong covalent bonds
But the molecules are held together by weak forces of attraction
What state is a simple molecule at room temp?
Liquid or gas
Properties of simple molecules
Very low melting and boiling points as only the intermolecular forces need to be broken
No conduction as no delocalised electron
Polymers
long chains of covalently bonded atoms
Graphene
1 layer of graphite
1 atom thick, making it 2d
Fullerene shape
Molecules of carbon, shaped like closed tubes or hollow balls. Mainly made up of carbon atoms arranges in 6,5,7s shapes.
Fullerene uses
Can be used to cage other molecules, this can be used to deliver drugs directly to the cells in a body
Huge surface area, so can be used as industrial catalysts
Nanotubes
Fullerenes, cylinders of graphene
conduct electricity
high tensile strength
used on tennis rackets to strengthen them
Simple molecular substances vs giant covalent
Simple molecular - Covalent compound held together by weak intermoleculer forces
Giant covalent - A massive compound of chained covalent bonds
What structure are metals?
Giant
What happens in metallic bonding?
The electrons in the outer shell of the metal are de-localised
What bonds are in metallic bonding?
Strong forces of electrostatic attraction between the positive metal ions and the shared negative electrons
These hold the metal atoms in a regular structure
WHat kind of compounds are held together by metallic bonding?
Metallic elements and alloys
What produces the characteristics in Metallic bonds?
The de-localised electrons
How strong are Metallic bonds?
The electrostatic forces between the metal ions and the de-localised sea of electrons are very strong, so need alot of energy to be broken
What are the physical properties of most metallic bonds?
high melting and boiling points
shiny solids at room temp
in soluble in water
dense in structure compared to non metals
malleable as layers can slide
good conductors
Non-metals general characteristics
dull, brittle
lower boiling points
dont conduct
lower boiling points
