Atomic Structure Past Paper Questions with Answers PDF

Okay, here is the converted text from the images into a structured markdown format. ### Q1 - Atomic Structure and the Periodic Table * All substances are made up of atoms. * Atoms are really tiny. * Atoms have a radius of about 0.1 nm ($1 \times 10^{-10} m$). * An atom is made up of 3 suba...

Okay, here is the converted text from the images into a structured markdown format. ### Q1 - Atomic Structure and the Periodic Table * All substances are made up of atoms. * Atoms are really tiny. * Atoms have a radius of about 0.1 nm ($1 \times 10^{-10} m$). * An atom is made up of 3 subatomic particles: 1. protons (p). 2. electrons (e). 3. neutrons (n). | Particle | Relative Charge | Relative Mass | | :------- | :-------------- | :------------ | | p | +1 | 1 | | n | 0 | 1 | | e | -1 | $\frac{1}{2000} = 0.0005$| ### The Nucleus * It is in the middle of the atom. * It contains protons and neutrons. * The nucleus has a radius of around $1 \times 10^{-14}$ m. * It has a positive charge because of the protons. * Almost the whole mass of the atom is concentrated in the nucleus. ### The Electrons * The electrons move around the nucleus in electron shells. * They are negatively charged and are tiny, but they cover a lot of space. * The volume of their orbits determines the size of the atom. * Electrons have virtually no mass. $^{23}_{11} Na$ * Atomic number tells you the number of protons in the atom. * mass number = number of protons + number of neutrons $Na$ $p = $ $e = $ $n = $ * So, to get the number of neutrons; mass number - atomic number. * Atoms are neutral - they have no charge overall. * This is because they have the same number of protons as electrons. * The charge on the electrons is the same size as the charge on the protons, but opposite, so charges cancel out. Q) Work out the number of protons, electrons, and neutrons in the following: 1. $^{39}_{19} K$ 2. $^{40}_{20} Ca$ 3. $^{16}_{8} O$ 4. $^{12}_{6} C$ 5. $^{14}_{7} N$ * In an ions, the number protons doesn't equal to the number of electrons. * Ions are charged particles; they lose or gain electrons. * Positive ions lose electrons and negative ions gain electrons. Q) Work out the proton number, electron number, and neutron number in the following ions? 1. $Na^+$ 2. $Ca^{2+}$ 3. $F^-$ 4. $N^{3-}$ 5. $S^{2-}$ 6. $O^{2-}$ 7. $Al^{3+}$ 8. $P^{3-}$ ### Elements * Element is a substance mad up of atoms, that all have the same number of protons in their nucleus. * There are about 100 different elements. * So, all the atoms of a particular element have the same number of protons, and different elements have atoms with different number of protons. * Atoms can be represented by symbols. C, O, Mg, Na, Fe, Pb. ### Isotopes * Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons. * So, isotopes have the same atomic number but different mass number. Ex: $^{12}_{6}C$ and $^{13}_{6}C$ * Because many elements can exist as a number of different isotopes, relative atomic mass ($A_r$) is used instead of mass number, when referring to the element as a whole. * This is an average mass taking into account the different masses and abundance (amounts) of all the isotopes that make up the element. $Relative \ atomic \ mass \ (A_r) = \frac{Sum \ of \ (Isotope \ abundance \times Isotope \ mass \ number)}{Sum \ of \ abundances \ of \ all \ the \ isotopes.}$ Q) A substance consists of atoms which all have the same number of protons and electrons but different numbers of neutrons. Explain why this substance is an element? (1 mark) Q) Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calculate the relative atomic mass of copper to 1dp? Q) An isotope of iron, Fe, has Fe-55, abundance 30.5% and Fe-57 - 69.5%, work out the relative atomic mass of iron? ### Compounds * When elements react, atoms combine with other atoms to form compounds. * Compounds are substances formed from two or more elements, the atoms of each are in fixed propositions throughout the compound and they are held together by chemical bonds. * Making bonds involve atoms giving away, taking or sharing electrons. Only the electrons are involved. * It's usually difficult to separate the original elements of a compound out again. * A compound which is formed from a metal and a non-metal consists of ions. * The metal atoms lose "electrons" to form positive ions; and the non-metal atoms gain electrons to form negative ions. * The opposite: charges of ions mean that they are strongly attracted to each other. This is called ionic bonding. Ex: Sodium chloride, magnesium oxide, calcium oxide. * A compound formed from non-metals consists of molecules. Each atom shares an electron with another atom - this is called covalent bonding.Ex:- Hydrogen chloride gas, carbon dioxide, water. * The properties of a compound are usually totally different from the properties of the original elements. Ex: Iron + Sulfur $\rightarrow$ Iron sulfide. (Lustrous magnetic metal) (Canice yellow powder) (Dull grey solid lump) ### Chemical formula 1. Carbon dioxide - 2. Water 3. Ammonia 4. Sodium chloride 5. Carbon monoxide 6. Hydrochloric acid 7. Calcium Chloride. 8. Sodium Carbonate 9. Sulfuric acid Q) How many atoms are in one particle of $Na_2CO_3$? Q) A compound has the formula CaCl Name the compound and the elements it contains? ### Chemical Equations * Word equation * Symbol equation 1. Methane + oxygen $\rightarrow$ carbon dioxide + water $CH_4 + O_2 \rightarrow CO_2 + H_2O$ 2. Magnesium + oxygen $\rightarrow$ magnesium oxide $Mg + O_2 \rightarrow MgO$ $H_2SO_4 + NaOH\rightarrow Na_2SO_4 + H_2O$ $Fe + Cl_2\rightarrow FeCl_3$ Q) Hydrogen and oxygen molecules are formed in a reaction where water Splits apart. For this reaction\ (a) stare the word equation\ (B) GIVO a balanced symbol equation ### Mixtures and Chromatography * Unlike in a compound, there is no chemical bond between the different parts of a mixture. * The parts of the mixture can be emer elements or compounds. they can be separated out by physical methods such as filteration, crystallisation and chromatography. * Air is a mixture of gases (mainly $N_2$, $O_2$, $CO_2$, and Ar) gases can be separated out fairly easily. * Crude oil is a mixture of different length hydrocarbon molecules. * properties of a mixture are just a mixture of the properties of the separate parts. ### Paper chromatography * The end result pattern Of spots called a Chromatogram. More Separation Techniques. * Filteration and crystallization are methods of separating mixtures. ### Filteration * This method is used to separate insoluble solids from liquids. * It can be used in purification as well. for example, solid impurities in the reaction mixture can be separaned out using filteration. * There are two ways to separate a soluble salt from a solution. * evaporation. * crystallization. ### Evaporation * pour the solution into an evaporating dish. * Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form. * keep heating the evaporating dish until all you have left and dry crustals. * Evaporation is a really quick way of separating a soluble salt from a solution but you can only use It if the salt doesn't decompose (break downg when Its heaned. Otherwise, you will have to lese crystallisation ### Crystallisation * pour the solution into an evaporating dish and gently neat the solution. * Some of the solvent will evaporate and the voivent will get more concentrared. * once some of the solvent has evaporated or when you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave the solution to 1001. * The salt should start to form corystals as it becomes insoluble in the cold, highly concentrared solution. * Filter the crystals out of the solution and leave them in a warm place to dry. you could also use a drying oven or a desiccator. * ROCK salt is simply a mixture of salt and sand. * Salt and sand both compounds. * but salt dissolves in water and sand doesn't. * Girind the mixture of salt and sand. * dissolve in warer. The salt will dissolve but the sand won't * Filter the mixture; the grains of sand won't fit through the fither paper. 50, try collect on. the paper instead. * The salt passes through the filter paper as its part of the solution. * Evaporcine the waner from the salt, so that it forms dry crystals.