C1 Flashcards
What is an element
All atoms are the same
How many elements are in the periodic table
100
What does each element represent
Different atoms with different symbols
What is a compound
Two or more elements chemically combined in a fixed proportion
What do we do to break compounds back into elements
We use chemical reaction
Different elements or compounds NOT chemically combined together
Mixtures
If we want to separate a ——- then we use physical techniques
Mixture
What physical techniques do we use to separate a mixture
Filtration crystallisation,distillation
Define molecule
Any elements chemically joined,can be same element unlike compound which needs different ones
What is an atom
Smallest part of an element, no overall electrical charge,all substances are made of atoms
Radius of an atom
0.1nm
What are physical separation techniques used for
Mixtures
What can physical techniques not be used to separate and why?
Elements in a compound because they are chemically combined in a fixed proportion
What is filtration
Used to separate insoluble solid from liquid
What is crystallisation
Used to separate soluble solid from liquid
What is simple distillation
Used to separate liquid from solid if we want to keep liquid
What is fractional distillation
Allows us to separate 2 different liquids
What is chromatography
Physical process used to separate mixtures
What does chromatography work
Because each chemical in mixture is attracted to the stationary phase to a different extent
What are atoms not
Divisible
Who invented the plumb pudding model
JJ Thompson
What does the plum pudding model show
An atom is a ball of positive charge with negative electrons embedded in it. Was WRONG!
Who did the alpha scattering experiment
Rutherford
Why did Rutherford experiment using a piece of gold foil
Can be hammered down to be a few atoms thick
Results from alpha scattering experiment (3 marks)
- most alpha particles went straight through the gold atoms
-some deflected (changed direction)
-bounced straight back
Most alpha particles went straight through gold atoms. Why?
Atoms are mainly empty space
Some alpha particles defelcted. Why?
Centre of atom must have positive charge- alpha particles close to this repell/ change direction
Alpha particles bounced straight back. Why?
Centre of atom must contain great deal of mass- now call this a nucleus
What did James chadwick discover
Nucleus also contained neutral particles called neutrons
Example of substance that you can filter
Silver chloride + water
AgCl= solid
H20= liquid
Example of substance you can crystallise
Sodium chloride + water
NaCl = aqueous- forms crystals
H20= water- evaporates
Equipment needed for filtration
Filter paper
Filter funnel
Beaker
Equipment needed for crystallisation
Beaker
Evaporating basin
Bunsen burner- if u wish to heat substance- don’t over heat otherwise compounds will start to break down
How does simple distillation work
- First evaporate liquid by heating
- we then condense water by cooling
Can fractional distillation work if liquids have same m.p/ b.p
No, otherwise we won’t be able to collect pure form
What is fractional distillation used for
To purify larger volumes of liquid e.g. crude oil- requires different equipment but principle is same
How do you know if a chemical is pure in chromatography?
Will produce a single spot in all solvents
What chemicals will move further up chromatography paper?
Chemicals that are weakley attracted to stationary phase
Why do we draw a line in pencil on chromatography paper
It’s insoluble
What is the solvent called in chromatography
Mobile phase because it doesn’t move
Soluble meanning
Can dissolve in water
Insoluble meanning
Can’t dissolve in water
Solute meanning
Dissolved in solvent
Solvent meaning
Dissolves solute resulting in solution
What’s the nuclear model (3)
- negative electrons around the edge
- tiny positive nucleus
- empty space
What was Niels Bohr model
- belived electrons orbited nucleus at specific distance (now call this orbit or energy levels/shells)
- several years later discovered protons- positive charge in nucleus
What was the final version of nuclear model
- atoms have no overall charge because number of electrons is the same as number of protons
What is radius of nucleus
1 x 10 ^ -14
Relative charge and mass of protons
Charge= +1
Mass= 1
Relative charge and mass of neutrons
Charge= 0
Mass= 1
Relative charge and mass of electrons
Charge= -1
Mass= very small
How does energy progress through the outer shells
shell- further away from nucleus= higher energy
What charge does the nucleus overall have
Positive because of protons
What happens if an atom absorbs electromagnetic radiation
An electron can move from a lower energy shell to a higher energy shell/level
How can electrons change energy levels/ shells
By absorbing or emitting electromagnetic radiation
What is the structure of how many electrons can be present in each shell
2, 8,8,18
The group number represents…
The number of electrons on outer shell
What is the relative atomic mass
Protons and neutrons- the bigger number
What is the atomic number
Smaller number
What did Döbereiner discover
- elements with similar properties occurred in 3s [triads]
- e.g. Lithium, sodium, potassium (all react rapidly with water)
- Chlorine, Bromine, Iodine (all reactive non-metal)
Work of Newlands…
Octaves
What was Newlands law of octaves
- arranged elements in order of Increasing atomic weight- every 8th reacts in similar way
- e.g. lithium, sodium, potassium
What was the problem with Newlands discovery
- by always sticking to exact order of atomic weight sometimes elements were grouped together when they had different properties
Who was the Russian scientist
Dmitri Mendeleeve
What did Mendeleeve do
- arranged elements by order of Increasing atomic weight
- If needed he would switch order of elements to fit pattern of other elements in same group
- realised some elements had not been discovered so left gaps in periodic table
What 3 things did Mendeleeve do that no other scientist did
- would switch order of specific elements to fit partern of other elements in same group
- realised some elements had not been discovered- left gaps
- predicted properties of undiscovered elements based on the group- he was correct elements discovered fit his periodic table
What are the differences between Mendeleevs table and modern periodic table
- protons had not been discovered- he ordered them with atomic weight ( elements could be in wrong order due to isotopes)
- modern includes noble gases which weren’t fully discovered when Mandeleev published his table
What are group 0 known as
Noble gases- monatomic gases (singles atoms- not bonded)
How many electrons do nobles gases have in outer shell
8- full, energetically stable except helium which has 2
List properties of Group 0 (4)
- inert: don’t react, non flammable
- colourless gases
- do not form molecules
- unreactive elements
What is the trend in noble gases (4 marks)
Boiling point Increases as you move down the group along with relative atomic mass
- atoms become larger intermolecular forces between atoms gets stronger- more energy Is needed to overcome the forces
Why does Boiling point Increases as you move down group 0
- atoms become larger intermolecular forces between atoms gets stronger- more energy Is needed to overcome the forces
How do noble gases react
Very unreactive as they have full outer shell
What are group 1 known as
Alkali metals
Group 1 have …. electrons in outer shell
1
How reactive are group 1 elements
Very reactive because they can lose the one electron in outer shell
Properties of Group 1 elements
- soft (can be cut with a knife)
- low density (first 3 are less dense than water)
- low m.p and b.p- decreases down the group
- form ionic compounds with non- metals
Describe the trend in group 1 elements
- Increasing reactivity as you move down the group- outer electron is more easily lost as attraction between the nucleus and electron decreases as electron is further from nucleus
- hence electron is lost easier as you move down group
- lower m.p. and b.p. as you move down
- higher relative atomic mass- atoms become larger
List the reactions of group 1 elements with water, oxygen and chlorine
Metal + water = metal hydroxide and hydrogen
Metal + oxygen= Metal oxide
Metal + chlorine = Metal chloride
Lithium + water =?
Lithium hydroxide + hydrogen
What is the formula for lithium reacting with water
2Li + 2H₂0 = 2LiOH + H₂
What are the observations for when lithium reacts with water
- fizzes steadily but furiously along surface
- slowly becomes smaller until dissappears
Sodium + water =?
Sodium hydroxide + hydrogen
Formula for sodium reacting with water
2Na +2H₂0 =2NaOH + H₂
What’s the observations when sodium reacts with water
- fizzes rapidly, melts to form a ball
- quickly becomes smaller until it dissappears- more violent than lithium
Potassium + water =?
Potassium hydroxide + hydrogen
Formula of potassium reacting with water
2K + 2H₂0 = 2KOH + H₂
Observations made when potassium reacts with water
- burns violently with a spark and lilac flame
- quickly melts to form a ball
- dissappears rapidly often with small explosion
- hot enough to ignite hydrogen gas
- very violent
Lithium + chlorine
Lithium chloride
Formula for lithium and chlorine
2Li + Cl₂ = 2LiCl
Sodium + chlorine
Sodium chloride
Potassium + Chlorine
Potassium Chloride
Formula for sodium and chlorine
2Na + Cl₂ = 2NaCl
Formula for potassium and chlorine
2K + Cl₂ = 2KCl
Observations made during reaction of lithium, potassium and sodium with chlorine
- act vigorously when heated in chlorine gas to form white metal chloride salts
- as you move down relativity increases so reaction with chlorine gas gets more vigorous
Lithium + oxygen
Lithium oxide
Sodium + oxygen
Sodium oxide
Potassium + oxygen
Potassium oxide
Formula for lithium reacting with oxygen
4Li + O₂ = 2Li₂O
Formula of sodium reacting with oxygen
4Na + O₂ = 2Na₂O
Formula for when potassium reacts with oxygen
4K + O₂ = 2K₂O
Observations made when group 1 alkaline metals react with oxygen
- burn vigorously when heated and placed in a gas jar of oxygen
- oxide forms white smoke
- as reactivity increases down group so does reaction with oxygen
What are group 7 called
Halogens
How are halogens found
Diatomic molecules joined together by single covalent bond
Properties of Group 7 [7]
- non metals
- coloured vapours: poisonous
- diatomic molecules
- form 1- ions
- ionic bonds with metal halide
- displacement reaction can occur between more reactive halogen and salt of less reactive one
- all have 7 electrons in outer shell
What colour is fluorine gas
Yellow- very reactive
What colour is chlorine gas
Dense green gas- fairly reactive
What colour is bromine
Red brown volatile liquid= dense
What colour is iodine
Purple vapour- dark grey crystalline solid
What happens to molecules as you move down group 7
Molecules become larger, intermolecular forces become stronger, more energy Is needed to overcome these forces
What happens to reactivity as you move down group 7
- halogens become less reactive- harder to gain extra electron because outer shell Is further from nucleus
What happens to m.p and b.p as you move down group 7
Increases along with relative atomic mass
At room temperature what is Flourine
Gas
At room temperature what is chlorine
Gas
At room temperature what is Bromine
Liquid
At room temperature what is Iodine
Solid
What happens when halogens react with metals
- produce salt- made of ions which are held together by ionic bonding
What does Halogen mean
Salt producing
What happens as you move down group 7 to the reactivity
Reactivity of elements decreases down group
What happens to force of attraction as you move down group 7
Force of attraction between nucleues and outer shell decreases
What happens when halogen reacts with hydrogen
Product= Compound called hydrogen halide
- gases at room temperature + dissolve in water to produce acidic solutions
What do group 7 form when they react with other non- metal atoms
Covalent compounds
In this reaction what is displaced:
Sodium bromide + fluorine = sodium fluoride + Bromine
- fluorine displaces Bromine
- because fluorine is more reactive than Bromine
What do group 7 elements form when they react with metals
Ionic compounds
What bonds do group 7 make
Ionic bonds with metal halide
What do group 1 elements form
Ionic bonds with non metals
Define Isotope
Atoms have same number of protons and electrons but different number of neutrons
Do isotopes have same chemical properties
Yes because they have same electronic structure
How do you find the relative atomic mass of isotopes
(Isotopic mass x%abundance ) +(Isotopic mass x % abundance) /100
E.g. chlorine has 2 isotopes
Cl 35- 75%
Cl 37- 25%
[(75 x 35) + (25 x 37)] /100
= 35.5
What elements react to form positive ions
Metals
What elements do not form positive ions
Non- metals except hydrogen
Compare transition metals with group 1 metals
- have higher m.p. (except Mercury)
- have higher densities
- are stronger
- are harder
- much less reactive so do not react as vigorously with oxygen or water
Properties of transition metals
- have ions with different charges
- form coloured compounds
- useful as catalysts
