C4 - Chemical Patterns Flashcards
What two properties are elements groups based on?
Relative atomic mass and properties
What did Johann Döbereiner do?
He noticed triads that linked patterns of the relative atomic masses of three elements
What did John Newlands do?
Noticed octaves where every eight element had similar properties
Why did scientists reject Döbereiner and Newlands’ ideas and accept Mendeleev’s?
The triads and octaves patterns didn’t work for all elements
New elements that were discovered fitted Mendeleev’s predictions
How was helium discovered?
Scientists looked at the light from the sun, split it using a prism and examined it’s line spectra noticing helium amongst it
What is the charge and mass for all three parts of an atom?
Proton, +1 charge, mass of 1
Neutron, 0 charge, mass of 1
Electron, -1 charge, mass of nearly 0
How can you work out the relative atomic mass of an element?
Proton number + neutron number = relative atomic mass
Give an example of how electron arrangements are used using Oxygen (8 electrons):
With dots e.g. 2.6
Number of electrons in an atom is _________ the proton number
Equal to
How many electrons are allowed in the first 4 shells and how can this information be found in the periodic table? (5)
In Shell 1=2, 2=8, 3=8, 4=18
Number of elements in a period = number of electrons allowed in that shell
The _____ an electron shell is to the nucleus, the _____ the energy level
Closer, lower
Period
A row in the periodic table
The _____ the proton number, the _____ the melting point and the _____ the boiling point
Higher, lower, higher
Describe the main properties of Elements in group 0 (2)
They have full outer shells and are Unreactive or inert gases
Link the number of outer shell electrons to an element’s likelihood to be metal or non metal:
Elements with up to 3 electrons in their outer shell are metals
Elements with 5 or more electrons in their outer shell are non metals
Group
A vertical column in the periodic table
Describe group 1 elements (3)
- Alkali metals
- Can be cut with a knife to reveal a shiny surface
- they tarnish quickly in moist air
How are group 1 elements stored? And why?
In oil, to prevent them from reacting with air or water
The _______ the group one element in the periodic table, the ______ reactive
Lower down = more reactive
What are the chemical hazards of group one metals and their products? (3)
They are flammable and their hydroxides are harmful and corrosive
What is the equation for the reaction of a group one element and water?
Metal + water -> metal hydroxide + hydrogen
The general balanced with state symbols equation for the reaction of group one elements is? (Using M to represent them)
2 M(s) + 2 H2O(l) -> H2(g) + 2 MOH (aq)
Where are the transition metals in the periodic table?
In the middle
Thermal disposition
Thermal disposition: when a substance breaks down into two or more substances
What are the general properties of metals? (5)
Good conductors, high melting + boiling points, shiny, dense, strong
What is the name of the group 7 elements?
The halogens
What is the appearance of chlorine at room temperature and what is the colour of its gas?
Pale green gas at room temperature
What is the appearance of bromine at room temperature and what is the colour of its gas?
Red-brown liquid at room temperature and reddish brown gas
What is the appearance of iodine at room temperature and what is the colour of its gas?
Dark grey solid at room temperature and purple gas
Diatomic molecules
Molecules of elements that always feature two atoms joined together
As you go down the halogen group the melting and boiling points ______
Increase
What are the chemical hazards of he halogens and how must they be used?
They are corrosive and toxic and must be used in a fume cupboard
What do group 7 elements react with metals to form?
Metal halides
Further down the halogen group, they become _____ reactive
Less reactive down the group
Displacement reactions
When a more reactive halogen takes the place of a less reactive halogen in a compound
What are the uses of chlorine and iodine?
They are used for sterilising wounds and water
Ionic compounds
Compounds made of ions of different elements
Crystal lattice
The regular pattern that ionic compounds are arranged in
What state do ionic compounds need to be in to conduct electricity and why?
They need to be dissolved or melted so that the ions are fee to move to the electrodes to complete the circuit
What are the main properties of ionic compounds? (3)
- Solid
- High melting points
- Soluble
Electrolysis
The process by which electricity is passed through ionic compounds to break them down into other substances
In electrolysis what is the charge of the anode?
Positive
In electrolysis what is the charge of the cathode?
Negative
In electrolysis what is the charge of the anions and what are they?
Negatively charged ions that are attracted to the anode
In electrolysis what is the charge of the cathions and what are they?
Positively charged ions that are attracted to the cathode
Covalent bonding
When two elements are bonded by sharing electrons
What are the properties of covalently bonded elements? (3)
Gases/ liquids with low melting and boiling points that don’t conduct electricity
Ionic bonding
When elements gain electrons from or lose electrons to other elements and become charged
What charge are elements of group 1 and elements of group 7 when ionised?
Group 1 = 1+ charge
Group 7 = 1- charge
Isotopes
Atoms of an element with a different number of neutrons
What does the state symbols: s, l, g and aq mean?
s = solid l = liquid g = gas aq = aqueous
Who arranged the periodic table?
Russian Chemist Dmitri Mendeleev
