Chemistry Paper 1: Topics 1-4 Flashcards
What are chemical equations
Show chemical changes. Reactants > products.
What are symbol equations
Show formulas of reactants and products. Must be same number of atoms of each element on both sides of the symbol equation. You can change the big number in front of the formula
In chemical equations involving ions, what do state symbols do?
Tell you the physical state of the substance
Aq = aqueous = dissolved in water
What are the chemical formulas of these common molecules: Water Carbon dioxide Chlorine Ammonia Hydrogen
H2O =water CO2 = carbon dioxide Cl2 = chlorine NH3 = ammonia H2 = hydrogen
What’s an ion? How can you work out the charges of ions?
Ions form when atoms gain or lose electrons
For single atoms use periodic table to see what charges their ions will form
What are the formulas of ions made up of these groups of atoms: Ammonium Hydroxide Nitrate Carbonate Sulfate
Ammonium = NH(little4)^+ Hydroxide = OH^- Nitrate = NO(little 3)^- Carbonate = CO(little 3)^2- Sulfate = SO(little 4)^2-
What’s an ionic equation
Only reacting particles and products are included
Look at the balanced symbols equation and take out aqueous ions present on both sides of the equation. Anything ionic and aqueous will break up into its ions in solution (in equation show all aqueous ions separately)
What’s a hazard and whats a risk
Hazard = something with the potential to cause harm/damage Risk = probability of being harmed when exposed to hazard
What do the following hazard symbols mean: Oxidising Environmental Hazard Toxic Harmful Highly flammable Corrosive
Oxidising = provides oxygen allowing other materials to burn
Environmental hazard = harmful to organisms + environment
Toxic = can cause death by swallowing, inhaling etc
Harmful = can caused irritation or blistering of skin
Highly flammable = catches fire easily
Corrosive = destroys materials, including living tissue
List the of atom theories over history
19th Century - solid spheres. Different spheres make different elements
1897 - Plum pudding model. Atom must contain electrons as has measurements of charge and mass
1909 - positively charged alpha particles at gold sheet. Most went through, some deflected, some sent backwards. Theory of nuclear atom, tiny positively charged nucleus at centre and cloud of negative electrons, rest is empty space.
Refined Bohr model - electrons exist in fixed orbit, each shell has a. Fixed energy
Whats the modern conclusion of structure of an atom?
3 subatomic particles: protons, neutrons, electrons.
Nucleus in middle of atom, contains neutrons + protons. Positively charged. Whole mass of atom is concentrated around nucleus
Electrons move around nucleus in electron shells. Size of their shell determines size of the atom.
Atoms have an atomic radius of about 10^-10m
Atoms have no overall charge, protons and electrons cancel out charges
What’s the atomic number and whats the mass number
Atomic number = how many protons (also electrons in neutral atom), every atom of an element has same atomic number
Mass number = total number of neutrons + protons in atom
Biggest number in nuclear symbol is always the mass number
What’s an isotope ?
Different forms of the same element. Have same number of protons but different numbers of neutrons ie same atomic number but different mass number
Different isotopes of an element appear in different isotopic abundances (quantities)
How do isotopes effect relative atomic mass (Ar) of the element
Ar of an element is the average mass of one atom of the element, compared to 1/12 of the mass of 1 atom of carbon - 12
On periodic table, Ar is the biggest number next to the element
If element has 1 isotope, Ar is the same as its mass number
Element has more than 1 isotope, Ar is average of mass numbers of all the different isotopes, taking into account how much there is of each one
How do you work out Ar of all atoms (isotopes) of an element
Multiply each relative atomic mass by its isotopic abundance and add up the results
Divide by sum of the abundances. If abundance’s given as percentages, this will be 100
Describe the early periodic table
Dmitri Mendeleev arranged about 50 elements to make ‘Table of elements’
Kept elements with similar properties in columns. Elements ordered by atomic mass.
Used properties of other elements to predict properties of undiscovered elements
Describe the modern periodic table
Shows elements in order of ascending atomic number
Elements with similar chemical properties form groups (columns)
Group number = number of electrons in outer shell. Group 0 is an exception, all have full outer shells, except helium which has 2 electrons in outer shell
Periods = the rows. Period number corresponds to number of shells
What does electronic configuration tell you
Electronic configuration 2.5 = 2 electrons in inner shell, 5 electrons in outer shell
What are ions. What are anions. What are cations.
Ions = charged particles. Can be single atoms or groups of atoms. Anions = negative ions. Forms when atoms gain electrons Cations = positive ions. From when atoms lose electrons
What does the charge of an ion tell you. How do charges of ionic compounds work
How many more/less electrons than protons
Eg 2 electrons lost, charge is ^2+
Overall charge of any ionic compound is zero. All negative charges balance out all positive charges. Use charges of individual ions present to work out formula of the ionic compound.
Why do elements form ions, and which ones are more likely to?
Elements in groups 1,2,6,7 are most likely to form ions.
Elements form ions in an attempt to get a stable electronic structure: full outer shell of electrons
What does it mean if ions end in ‘ate’ or ‘ide’
‘Ate’ = negative ions containing oxygen and at least 1 other element ‘Ide’ = negative ions containing only one element (apart from hydroxide ions which are OH^-)
What’s ionic bonding
When a metal and non metal react together, the metal atom loses electrons to form a cation and the non metal gains these electrons to form an anion. These oppositely charged ions are strongly attracted to one another by electrostatic forces. This is an ionic bond
What can you use to show ionic bonding
Dot and cross diagram
Have original atoms, one with electrons represented with dots, the other with crosses. Little arrow to show where electrons will move from and to > the new ions, each has a square bracket around it. Electrons shown in their new places. Charges written outside bracket. Electronic configuration of each ion shown underneath.
What are the properties and structure of ionic compounds?
Always have giant ionic lattice structure. Strong electrostatic forces of attraction between oppositely charged ions in all directions. Throughout lattice oppositely charged ions will alternate.
High melting boiling points due to strong attraction between ions. Solid ionic compounds don’t conduct electricity, ions fixed in place. When melted, ions free to move, so will carry electric current.
Many dissolve easily in water, ions free to move in solution.
What’s covalent bonding and how does it relate to simple molecular substances
A covalent bond is a strong bond that forms when a pair of electrons is shared by two atoms
Covent bonding forms simple molecular substances and giant covalent structures
Simple molecular substances are made up of molecules containing a few atoms joined by covalent bonds.
What are the covalent bonds in the following simple molecular substances: Hydrogen Hydrogen chloride Water Oxygen Methane Carbon dioxide
Hydrogen = H2 = 2 hydrogen atoms form single covalent bond
Hydrogen chloride = HCl = H+Cl atoms form single covalent bond
Water = H2O = H+H+O, 2 single covalent bonds
Oxygen = O2 = O+O, double covalent bond
Methane = CH4 = C+H+H+H+H, 4 covalent bonds
Carbon dioxide = CO2 = O+C+O, 2 double covalent bonds
What’s a double covalent bond
A bond made of 2 shared electron pairs
What are the properties of covalently bonded simple molecular substances
Substances containing covalent bonds are usually simple molecular:
- atoms within molecules held together by strong covalent bonds. Forces of attraction between molecules weak.
Melting boiling points low as only need to part molecules
As molecules get bigger, strength of intermolecular forces increases
Don’t conduct electricity, no free electrons or ions
Some are soluble, some aren’t
What are polymers
Molecules made of long chains of covalently bonded carbon atoms, formed when many monomers join together
Monomers = lots of small molecules
What are the properties of most giant covalent structures
All atoms bonded to each other by strong covalent bonds. Very high melting boiling points due to this.
Generally don’t contain charged particles, so don’t conduct electricity (except graphite and Graphene)
Aren’t soluble in water
State and describe three carbon based giant covenant structures
Diamond: made of network of carbon atoms, each form 4 covalent bonds. High melting boiling point, atoms held in rigid lattice structure. Doesn’t conduct electricity. Used to strengthen cutting tools
Graphite: each carbon atom forms 3 covalent bonds, creating sheets of carbon atoms arranged in hexagons. No covalent bonds between layers so they’re free to move over each other. Ideal lubricating material. High melting boiling point due to covalent bonds. Each carbon has 1 delocalised electron, so graphite can conduct electricity
Graphene: a type of fullerene, is 1 layer of graphite. Sheet is 1 atom thick, so Graphene is a 2D compound.
What does it mean if an electron is delocalised?
It’s free to move
What are Fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls. Mainly made of carbon atoms arranged into hexagons. Can contain pentagons or heptagons.
Fullerenes structure forms around an atom or molecule, which is trapped. Could be used to deliver drugs directly to cells.
Have huge surface area, could be used as industrial catalysts, with individual catalyst molecules attached to the fullerenes.
Name and describe two examples of fullerenes
Buckminster Fullerenes, C60
- Molecular formula C60, forms hollow sphere of 20 hexagons and 12 pentagons. Stable molecule. Forms soft black crystals
Nanotubes are Fullerenes
- tiny cylinders of Graphene, conduct electricity. High tensile strength (doesn’t break easily when stretched), can be used to strengthen equipment without adding much weight
Describe metallic bonding
Metals consist of a giant structure. Electrons in outer shell of metal atoms are delocalised. There are strong forces of electrostatic attraction between positive metal ions and shared negative electrons, these forces hold atoms together in regular structure
Metallic elements and alloys are compounds held together by metallic bonding
All metals have metallic bonding, so similar basic physical properties. Metals usually lose electrons to gain full outer shells.
Describe properties of compounds held together by metallic bonding
The delocalised electrons produce all properties of metals
Most compounds with metallic bonds have high melting boiling points. Usually shiny solids at room temperature. Not soluble in water. Denser than non metals, ions in metallic structure packed closely. Layers of atoms in pure metal can solide over each other, meaning metal is malleable (can be shaped)
Delocalised electrons carry electrical current + thermal energy through material, good conductors of electricity + heat
What’s Relative Formula Mass
Mr of a compound is the relative atomic masses (Ar) of all atoms in its formula added together
The Mr of compound is equal to mass in grams of 1 mole of the compound
What’s empirical formula
Empirical formula of a compound tells you the smallest whole number ratio of atoms in the compound
Work out how many moles of each element there are. Then work out the smallest whole number ratio between the moles of all the elements/atoms to get the empirical formula
What’s molecular formula
Molecular formula is the ratio of the elements in a compound given normally, eg glucose is C6H12O6
Use empirical formula and Mr to find molecular formula of a compound
Find Mr of compound. Divide Mr of compound by the Mr of the empirical formula to get Ans. Molecular formula = everything in empirical formula x Ans
