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Terms in this set (98)
What is the modern periodic table based on?
The Russian chemist (Dmitri) Mendeleev's ideas
How did Mendeleev structure the periodic table?
He arranged elements into groups and periods (based on their relative atomic mass and patterns in their properties
What did Döbereiner notice?
'Triads' between elements that linked patterns of the relative atomic masses for 3 elements
What did Newlands notice?
An 'octaves' pattern, where every eighth element had similar properties
What happened when new elements were discovered?
They fitted Mendeleev's predictiins
When elements are heated they emit coloured flames, what can they do to these flames?
The colour of the light it emits can be split into a line spectrum that is unique to each elemnt
What happened because of the development of spectroscopy?
The discovery of some elements (helium was discovered when chemists looked at the line spectrum from the sun)
What do all atoms of a particular element have?
The same number of protons
What does the number of protons + the number of neutrons equal?
Relative atomic mass
What are 2 main properties of elements in group 0?
They have full electron shells and are inert (very unreactive)
What is the same on an element as the group number it is in?
It has the same amount of electrons in its outer shell as the group number it is in.
What are atoms of elements with up to 3 electrons in their outer shell?
What are atoms of elements with 5 or more electrons in their outer shell?
What are elements with a full outer shell?
What is group 1 on the periodic table called?
The alkali metals
What are 2 main properties of group 1 elements?
They are soft metals that can be cut with a knife (the freshly cut surface is shiny but it tarnishes quickly in most air by reacting with the oxygen)
What charge do group 1 elements all get when formed into ions?
A 1+ charge because they lost an electron
Why does the reactivity increase down the group 1 elements as the atoms get bigger?
The outer electron is easier to lose if the atom is bigger
What do all group 1 elements react with?
Water - the reaction gets more violent as you move down group 1
What are the products when group 1 elements react with water?(2)
• Hydrogen gas (it 'pops' when lit)
• Metal hydroxide (an alkali and turns pH indicator blue)
Why should group 1 metals be kept away from water and naked flames?
They are flammable and their hydroxides are harmful and corrosive
What is the general word equation for the reaction of group 1 elements with water?
Metal + water --> metal hydroxide + hydrogen
What is the general symbol equation, using 'M' to stand for any of the group 1 metals, for the reaction of group 1 elements with water?
2M (s) + 2H20 (l) --> H2 (g) + 2MOH (aq)
What does sodium react vigorously with?
Chlorine - to give a yellow flame and it makes a white solid (sodium chloride) ; other group 1 metals react in a similar way and the reactions are faster down the group
What is the word equation for the reaction between sodium and chlorine?
sodium + chlorine --> sodium chloride
What is the symbol equation for the reaction between sodium and chlorine?
2Na (s) + Cl2 (g) --> 2NaCl (s)
What are the elements in group 7 called?
What is the appearance of chlorine at room temperature and the colour of its gas?
Pale green gas ; pale green
What is the appearance of bromine at room temperature and the colour of its gas?
Red-brown liquid ; reddish-brown
What is the appearance of iodine at room temperature and the colour of its gas?
Dark grey solid ; purple
What do the halogens all contain?
Diatomic molecules - they have 2 atoms joined together in each molecule
What are some properties of halogens?
They are corrosive and toxic (so they need to be used in a fume cupboard)
What do group 7 elements when reacted with alkali metals and with other metals form?
How does the reactiveness of the elements change as you go down group 7?
They become less reactive
When do displacement reactions happen? Give an example and explain.
When a more reactive halogen takes the place of a less reactive halogen in a compound ;
e.g. chlorine is more reactive than bromine and displaces bromine from potassium bromide solution; bromine is less reactive than chlorine and cannot displace chlorine from potassium chloride solution
For non-metals, what does it mean if the atom is smaller (very few electron shells)?
It's more reactive --> the smaller the element the more reactive
What is a property of a compound, made from a group 1 element and group 7 element, in terms of melting point, and what are they called (& why)?
They are a solid and have high melting points ; they are called ionic compounds because they contain charged particles/ions that are arranged in a regular pattern called a crystal lattice
Are ionic compounds soluble?
Yes , when in water, and can conduct electricity when melted
What happens when an ionic crystal melts or dissolves in water?
The ions are free to move
What does dry air contain?
Non-metal elements and small amounts of non-metal compounds
What is the symbol form of nitrogen and what is its percentage in dry air?
N2 ; 78%
What is the symbol form of oxygen and what is its percentage in dry air?
O2 ; 21%
What is the symbol form of argon and what is its percentage in dry air?
Ar ; 1%
What is the symbol form of carbon dioxide and what is its percentage in dry air?
CO2 ; 0.04%
When does a covalent bond form?
When atoms share a par of electrons (only non-metals)
Why can't pure molecular substances conduct electricity?
Molecules of elements and compounds have no electrical charge
What are the forces like BETWEEN molecules for small covalent molecules?
What are the forces like WITHIN molecules (covalent bonds)?
What is the Earth's hydrosphere?
All the water on Earth ; its mostly water with some dissolved compounds called salts
What happens to dissolved salts, when water evaporates?
They form solid crystals
What are salts?
Ionic compounds ; they are arranged in a giant 3D pattern called a lattice.
What can the solutions of some ionic compounds make?
A precipitate of an insoluble compound when they mix. (The colour of the precipitate can be used to identify the ions in the compounds).
What does adding an alkali to different positive metal ions do?
Gives different colours of precipitates
How are negative carbonate ions identified?
By adding dilute acid and looking for fizzing (effervescence)
Why do carbonates fizz when an acid is added?
Carbon dioxide gas is made in the reaction
When do precipitates form?
When an insoluble solid is made in the reaction
What is the lithosphere?
It's the rigid outer layer of the Earth made up of the crust and upper mantle which contains rocks and minerals.
What are minerals?
Solids with atoms or ions arranged in a regular lattice
In what form are most of the silicon and oxygen on Earth?
They are joined together in the Earth's crust as silicon dioxide - e.g. in mineral quartz
What are ores?
Rocks that contain metal minerals
What do some ores contain?
How can carbon, zinc and iron be extracted from their ores?
By heating their metal oxides with carbon - carbon reduces the metal oxide by taking away oxygen
Why is extracting metals by heating their oxides with carbon a redox reaction?
Both oxidation and reduction happen
Why does diamond have a very high melting and boiling point and doesn't dissolve in water?
The bonds in diamond are very strong and need a large amount of energy to break them
Why does silicon dioxide have similar properties to diamond?
They both have a giant covalent structure
In diamond, what is each carbon atom covalently bonded to?
Four other atoms in a tetrahedral 3D lattice
Why can graphite conduct electricity?
There are free-moving electrons between the sheets
What is the equation to work out the percentage of metal in a mineral?
(total mass of metal atoms / gram formula mass) x 100
Why is electrolysis used to extract more reactive metals?
Their oxides cannot be reduced by carbon
Why do metals form at the negative electrode (cathode)?
Positive metal ions are attracted to the negatively charged electrode (opposites attract)
Why do negative ions such as chloride an oxide move to the positively charged electrode (anode)?
The negatively charged ions are attracted to the positive electrode (anode) - this is where non-metals form such as chlorine and oxygen
Why is a lot of energy needed to melt and reshape metallic bonds?
They have a strong bond
When solid metals become ions, what happens to the outer shell?
The outer shell of electrons form a 'sea of electrons' allowing them to move freely
When can ionic compounds only conduct electricity?
When they are molten or in a solution
What can waste poisonous metals from mines do?
Destroy habitats , damage soil and water sources
What can extracting metals make?
Pollutant gases that cause acid rain
Give 3 examples of poisonous metals:
What do some minerals contain?
Compounds of metals with sulfur
What colour does acids turn litmus?
What colour does alkalis turn litmus?
What are pH numbers for acids?
What are pH numbers for alkalis?
Acids react with many metals to form a salt and hydrogen gas; using calcium and hydrochloric acid, give the word equation for this reaction:
calcium + hydrochloric acid --> calcium chloride + hydrogen
Acids react with metal oxides and hydroxides to form a salt and water; using magnesium oxide and sulfuric acid for one and sodium hydroxide and nitric acid for another, give the word equations for both reactions:
1) magnesium oxide + sulfuric acid --> magnesium sulfate + water
2) sodium hydroxide + nitric acid --> sodium nitrate + water
Acids react with metal carbonates to form a salt, water and carbon dioxide; using calcium carbonate and hydrochloric acid, give the word equation for this reaction:
calcium carbonate + hydrochloric acid --> calcium chloride + water + carbon dioxide
Salts are ionic compounds, what do they contain?
A positively charged metal ion and a negative ion from the acid.
What is always made when an acid reacts with an alkali?
A salt and water
What do all acids contain when dissolved in water?
Hydrogen ions (H+) ; the pH of an acid is related to the concentration of H+ ions in the acid solution
What happens in the ionic equation during neutralization reactions?
The negative ion from the acid and the positive ion from the alkali are left in the solution to form the salt
What happens in an EXOTHERMIC reaction?
It gives out heat energy so the temperature of the surroundings rises
What happens in an ENDOTHERMIC reaction?
It takes in heat energy so the temperature of the surroundings falls
What can filtration be used to do ?
Separate a solid from a liquid or from a solution
What is crystallization used for?
To purify impure solid crystals
What are the 5 steps to crystallization?
What is the actual yield?
The mass of the product measured at the end of the experiment
What is the theoretical yield?
The predicted yield calculated from the amount of reactants used and the equation for the reaction.
What is the equation to find the percentage of yield?
(actual yield/ theoretical yield) x 100
What can a colorimeter do?
It can be used to follow the rate of a colour change
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