Flashcards in Chapter 1 - Key Concepts In Chemistry Deck (51):
What are the chemical formulas for: Water, Carbon Dioxide, Chlorine, Ammonia, Hydrogen and Oxygen?
H2O, CO2, Cl2, NH3, H2, O2
What. Are the ionic formulas for: Ammonium, Nitrate, Sulfate, Hydroxide, Carbonate
NH4(+), NO3(-), SO4(2-), OH(-), CO3(2-)
Note: the positives and negative as in the brackets are the charges and would normally be written like you would write ‘squared’ in maths
Name the four models of the atoms in order and there inventor
Atoms as solid spheres - John Dalton
The Plum Pudding Model - J J Thompson
The Nuclear Atom theory - Ernest Rutherford
The Bohr Model - Niels Bohr
Describe John Dalton’s atom model
Atoms were solid spheres and different spheres make up different elements
Describe J J Thompson’s Plum Pudding Model
There was a positively charged mass (the ‘pudding’) with negatively charged electrons scattered through it
Describe Rutherford’s atom model
A tiny positively charged nucleus at the centre surrounded by a ‘cloud’ of negative electrons -most of the atom is empty space
Describe Niels Bohr’s atom model
The electrons can only exist in fixed orbits (shells) and not anywhere in between them. Each shell has fixed energy. It is pretty close to the current model of the atom.
What are the three subatomic particles? What are their charges? What are their relative masses?
Protons, Neutrons and Electrons
P=+1, N=0, E=-1
P=1, N=1, E=negligible
What does the atomic number describe about an element? Does it have another name?
The number of protons in the atom (and electrons)
Th proton number
What are isotopes?
Different forms of the same element - they have the same number of protons but a different number of neutrons.
What makes isotopes the same element?
The atomic number (protons) is the same but its only the atomic mass number (neutrons) which changes
What is Ar? How can it be calculated?
Relative atomic mass. It is the average mass number from the isotopes.
(Isotopic mass X isotopic abundance) + (Isotopic mass X abundance)
Who arranged the First version of the Periodic Table and when?
Dimitri Mendeleev, 1869
What do the groups on the periodic table show?
How many electrons an element has on its outer shell
The elements with similar properties
What do the periods show in the periodic table?
How many electron shells/orbits/energy levels the element has
What does the atomic number represent? Does it have another name?
The number of protons (and also electrons)
The proton number
What does the relative atomic mass number represent? Does it have another name?
The number of protons and neutrons
The mass number, the atomic mass number
What are ions?
Charged particles. They can be single atoms or groups of atoms.
Which elements are most likely to form ions?
What happens to the electrons in ionic bonding?
They are transferred from a metal to a non-metal. The oppositely charged ions are strongly attracted to each other by electrostatic forces of attraction. This attraction is called an ionic bond.
Which type of diagram can we use to show ionic bonding?
Dot and Cross diagrams
How are ionic compounds always arranged?
In giant ionic lattices. There are very strong electrostatic forces of attraction between oppositely charged ions in all directions
What are the properties of ionic compounds?
High melting and boiling points - strong electrostatic forces of attraction between ions. It takes a lot of energy to overcome this attraction
They conduct electricity in solution or when molten - the ions (which are charged) are free to move and carry charge through the structure
They are brittle - the layers in the lattice can get moved so that the like ions are next to each other and then the layers repel
What happens in covalent bonding?
When electrons are shared between two or more atoms, a strong bond is formed.
Name some examples of simple covalent substances
You need to know these for your exam
H2, H2O, CH4, HCL, O2, CO2
(Hydrogen, Water, Methane, Hydrogen Chloride, Oxygen, Carbon Dioxide)
Name the properties of simple covalent substances
Simple molecular structures of only a few atoms
Very strong covalent bonds within the molecules but weak intermolecular forces between them
Low melting and boiling points - weak intermolecular forces
Usually liquid or gas at room temperature
The bigger the molecule, the greater the strength of the intermolecular forces so the more energy required to break them and therefore higher melting and boiling points
Don’t conduct electricity - no free electrons or ions
What are monomers and polymers?
Monomers are molecules made from one atom. Polymers are made up of long chains of covalently bonded monomers.
Give some properties of Giant Covalent Structures
Strong Covalent bonds between all atoms
High melting and boiling points as lots of energy is needed to break the covalent bonds
Generally don’t contain charged particles so don’t conduct electricity (apart from graphite and graphene)
Aren’t soluble in water
Give some properties of diamond
Made up of carbon atoms with four covalent bonds each
High melting and boiling point because the strong covalent bonds require lots of energy to break
Rigid lattice structure make it a very strong/hard material - it is often used to strengthen cutting tools
No free electrons or ions so it doesn’t conduct electricity
Give some properties of graphite
Made from carbon atoms which have three covalent bonds each - this creates ‘sheets’ of carbon atoms arranged in hexagons
No covalent bonds between layers - only held together weakly with intermolecular forces so they’re free to move over each other. This makes it soft and slippery so it’s ideal as a lubricant
High melting and boiling point - the covalent bonds in the layer need lots of energy to break
Only three of each carbon’s four outer electrons are used in bonds so each carbon atom has one electron that’s delocalised and can move. It can conduct electricity and is often used to make electrodes
Give some properties of graphene
It is a type of fullerene and is one layer of graphite
It’s a sheet of carbon atoms joined together in hexagons
It is a two dimensional compound as it is only one atom thick.
What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls.
Mainly made from carbon atoms arranged in hexagons but can also contain pentagons or heptagons.
Can be used to ‘cage’ other molecules - they can form around another molecule, trapping it. This could be used to deliver a drug directly to cells in the body.
They have a huge surface area so they can make great industrial catalysts.
What is the buckminsterfullerene (all one word)? A.k.a. Bucky ball
Molecular formula C60
Hollow sphere made from 20 hexagons and 12 pentagons
Stable molecule that forms soft brownish-black crystals
What are nanotubes?
Tiny cylinders of graphene
high tensile strength - don’t break when stretched so can be used to strengthen materials without adding much weight
E.g. Can be used to strengthen sports equipment which needs to be strong yet lightweight
What is metallic bonding?
The electrons in the outer shell are delocalised.
There are strong electrostatic forces of attraction between the positive metal ions and the shared negative electrons.
The electrostatic forces of attraction hold the atoms together in a regular structure and are known as metallic bonding. Metallic bonding is very strong
It’s the delocalised electrons in metallic bonding which produce ALL the properties of metals.
Give some properties of metals
High melting and boiling points - the electrostatic forces of attraction between the metal ions and sea of delocalised electrons are very strong so need lots of energy to be broken. This also means they are shiny solids at room temperature and aren’t soluble in water
More dense than non-metals as the ions in the metallic structure are packed close together.
They are malleable - layers in a pure metal can slide over each other so they can then be hammered or rolled into flat sheets
They are good conductors of electricity or heat - the delocalised electrons can carry electrical current or thermal energy throughout the structure
They are malleable because the layers can slide over each other
Good conductors of electricity and heat - the delocalised electrons carry current and thermal energy through the material.
Give some differences between metals and non-metals
Metals have metallic bonding but non-metals don’t
Non-metals form a variety of different structures so have a wide range of chemical and physical properties
Non-metals tend to:
-be more brittle
-have lower melting and boiling points
-have a lower density
-generally not conduct electricity
Non-metals also tend to gain electrons to form full outer shells (outer shells are generally over half-full in elemental form) whereas metals tend to lose electrons to gain full outer shells (their outer shells are generally under half-full)
What is the Conservation of Mass and what does it mean?
Atoms cannot be destroyed or created.
During a chemical reaction there are the same number and types of atoms on each side of the reaction equation. The mass will not change throughout the reaction.
What is a good way to show the Conservation of Mass? What is this?
A precipitation reaction.
Happens when two solutions react and a precipitate (insoluble solid) is formed in the solution
What has happened in a Conservation of Mass experiment if the mass increases in an unsealed reaction vessel? What if the mass decreases?
At least one of the reactants is a gas which is found in air and the products are solid, liquid or aqueous. Since the vessel is unsealed the gas not trapped and its mass couldn’t be measured.
Some or all of the reactants are are solids, liquids or aqueous and at least one of the products is a gas. The gas is no longer contained so the mass decreases
What is the relative formula mass?
Mr (the ‘r’ is written below the line) - the relative atomic masses of each of the atoms in the formula are added together.
E.g. MgCl2: Ar of Mg=24, Ar of Cl=35.5
Mr(MgCl2)=24 +(2 x 35.5)
= 24 + 71
What is the empirical formula?
The smallest whole number ratio of atoms in the compound
E.g. C6 H12 O6
What is the molecular mass? How do you work it out?
The form a compound is found in (the number of each atom in the compound)
Find the empirical formula, divide the relative formula mass (Mr) by the relative formula mass (Mr) of the empirical formula. Multiply everything in the empirical formula buy the result
What is a mole? What is Avogadro’s Constant and why is it useful?
A mole is a number of particles equal to Avogadro’s Constant.
It is useful because 1mol=number of grams of the the relative particle (Ar or Mr) mass of the element or compound
What are the outer shell electrons also called?
What did Mendeleev do? How do we know now that he was right?
Organised the first periodic table of elements in 1869. He and left gaps in it which were undiscovered elements at the time, they are now all discovered
Which one group did Mendeleev miss of the periodic table?
Group 8, the noble gases
Why did Mendeleev switch some of the elements around/ out of proton order?
To keep them in groups that fitted their similar properties
Why did scientists not believe Mendeleev at the time?
There were anomalies that did not look accurate at the time, he had left gaps for undiscovered elements, some boxes had 2 elements in, some were unreactive, he had metals and non metals in the same box
How did Mendeleev know there must be an undiscovered element?
Because he knew there must be certain elements in certain groups because of their properties and for that to happen there would be one or more in group that were undiscovered in order to shift some other elements along to another/ the next group