S3 Chemistry Final Exam Revision Guidelines - PDF

S3 Second Term Uniform Test Revision Guidelines 1 Important notes Term 1 Notes 1.2 n Important value of an atom Mass number (A) Number of protons + Number of neutrons Atomic number...

S3 Second Term Uniform Test Revision Guidelines 1 Important notes Term 1 Notes 1.2 n Important value of an atom Mass number (A) Number of protons + Number of neutrons Atomic number (Z) Number of protons n AXZ notation Mass number Electrical charge A n+ Z X Chemical symbol Atomic number n Examples Particles Discussion # of p+ Atomic number ~ 12 "# !"𝑀𝑔 # of n (Mass number – Atomic number) = 25 – 12 = 13 - # of e Electrically neutral ~ p+ = e- = 12 S3 Second Term Uniform Test Revision Guidelines 2 Term 1 Notes 1.3 n Electron shell o Maximum number of electrons can be held in the nth shell = 2n2 n Electronic structure o Electronic structure of the first 20 elements Element Element H 1 Na 2, 8, 1 He 2 Mg 2, 8, 2 Li 2, 1 Al 2, 8, 3 Be 2, 2 Si 2, 8, 4 B 2, 3 P 2, 8, 5 C 2, 4 S 2, 8, 6 N 2, 5 Cl 2, 8, 7 O 2, 6 Ar 2, 8, 8 F 2, 7 K 2, 8, 8, 1 Ne 2, 8 Ca 2, 8, 8, 2 n Noble gas electronic arrangement o Chemical species with noble gas electronic arrangement ~ Stable o Example O atom (2, 6) O2- ion (2, 8) K atom (2, 8, 8, 1) K+ ion (2, 8, 8) Unstable Stable (~ Ne atom) Unstable Stable (~ Ar atom) S3 Second Term Uniform Test Revision Guidelines 3 Term 1 Notes 2.1 n Important information from the position in the Period Table o Positions are arranged by atomic number ~ Related to the electronic arrangement o Summary Similarity Examples Period Same number of occupied electron shell Na: 2, 8, 1 Mg: 2, 8, 2 Group Same number of outermost shell electrons Cl: 2, 8, 7 Br: 2, 8, 18, 7 n General properties for group VII elements o Physical properties Ø Coloured substances ~ Colour becomes deeper and deeper down the group n General properties for group 0 elements o Physical properties Ø Colourless gas Term 1 Notes 2.2 n Classification o Metals, non-metals and semi-metals Term 1 Notes 2.3 n Unstable elements o Unstable = Without a noble gas electronic arrangement S3 Second Term Uniform Test Revision Guidelines 4 Term 1 Notes 3.1 n Electronic diagram o Show the number of electrons in each electron shell n Some examples XX He B X XX XX Helium atom Boron atom Term 1 Notes 3.2 n Charge of ions formed and the periodic table I II III IV V VI VII 0 +1 +2 +3 -3 -2 -1 Term 1 Notes 3.3 n Chemical formula of ionic compounds o Charge of cations and anions should be balanced o Examples Cl- O2- N3- + Na NaCl Na2O Na3N Mg2+ MgCl2 MgO Mg3N2 Term 1 Notes 3.4 n Bonds and line representation of covalent bonds ⨯⨯ ⨯ ⨯ H Cl⨯ O O ⨯⨯ ⨯ ⨯ ⨯ N N ⨯ ⨯ H Cl O O N N Single bond Double bond Triple bond S3 Second Term Uniform Test Revision Guidelines 5 Term 2 Notes 0.1 n Classification of pure substances o Element Ø Only one kind of atom o Compound Ø More than one kind of atoms chemically bonded together n Mixture o More than one constituent physically mixed together ~ Retain their own properties Term 2 Notes 1.1 n Composition of air o 78 % Nitrogen (N2), 21 % Oxygen (O2), 0.93 % Argon (Ar), 0.04 % Carbon dioxide (CO2) o Trace Other noble gases (He / Ne …) n Isolating method = Fractional distillation of liquid air Term 2 Notes 2.1 n Sea water o Mixture of element and compound n Electrolysis of sea water Cl2 NaCl Na+ + Cl- H 2O H+ + OH- H2 NaOH S3 Second Term Uniform Test Revision Guidelines 6 Term 2 Notes 2.2 n Some results for the flame test Compounds of Flame color Sodium (Na) Golden yellow flame Potassium (K) Lilac flame Copper (Cu) Bluish green flame Calcium (Ca) Brick red flame n Steps to carry out flame test 1. Clean the tip of the platinum wire with concentrated hydrochloric acid 2. Dip the tip of the wire into the sample 3. Put the tip of the wire into a non-luminous flame Term 2 Notes 3.1 n Substances Chemical formula Substance CaO (s) Quicklime Ca(OH)2 (s) Slaked lime Ca(OH)2 (aq) Limewater Chalk CaCO3 (s) Limestone Marble S3 Second Term Uniform Test Revision Guidelines 7 Term 1 Notes 1.2 1. What is the number of neutrons in "# !!𝑁𝑎? [Ans: 23 – 11 = 12] 2. State the atomic number and mass number of #! !$𝑃. [Ans: Atomic number = 15 Mass number = 31] 3. What is the mass number of #% !%𝐾 ? [Ans: 39] 4. What is the atomic number of '" "&𝐶𝑎? [Ans: 20] 5. State the number of protons and neutrons of (#𝐿𝑖. [Ans: Protons = 3 Neutrons = 7 – 3 = 4] 6. State the number of protons, neutrons and electrons in #' !*𝑆. ") [Ans: Protons = 16 Neutrons = 34 – 16 =18 Electrons = 16 – (– 2) = 16 + 2 = 18] 7. State the number of protons, neutrons and electrons in #% !%𝐾. + [Ans: Protons = 19 Neutrons = 39 – 19 = 20 Electrons = 19 – (1) = 18] S3 Second Term Uniform Test Revision Guidelines 8 Term 1 Notes 1.3 1. What is the maximum number of electrons can exist in the 2nd electron shell? [Ans: 2 (2)2 = 2 x 4 = 8] 2 (Note: The formula is 2n.) 2. What is the maximum number of electrons can exist in the 4th electron shell? [Ans: 2 (4)2 = 2 x 16 = 32] 3. What is the electronic arrangement of a hydrogen atom (H)? [Ans: 1] 4. What is the electronic arrangement of a magnesium atom (Mg) and a magnesium ion (Mg2+)? [Ans: Mg: 2, 8, 2; Mg2+: 2, 8] 5. What is the electronic arrangement of a potassium atom (K)? [Ans: 2, 8, 8, 1] S3 Second Term Uniform Test Revision Guidelines 9 Term 1 Notes 2.1 1. The electronic arrangement of an atom is 2, 8, 2. To which group and period of the Periodic table does it belong to? [Ans: Group II, Period 3] 2. The electronic arrangement of an atom is 2, 5. To which group and period of the Periodic table does it belong to? [Ans: Group V, Period 2] 3. The electronic arrangement of an atom is 2, 8, 8, 1. To which group and period of the Periodic table does it belong to? [Ans: Group I, Period 4] 4. State the physical appearances of chlorine and argon under room conditions. [Ans: Chlorine is a yellowish green gas. Argon is a colourless gas.] 5. State the physical appearances of fluorine under room conditions. [Ans: Pale yellow gas.] 6. What is the semi-metal in period 2? [Ans: Boron] 7. (a) What is the semi-metal in period 3? [Ans: Silicon] (a) To which group do the element belong to in the Periodic table? [Ans: Group IV] 8. What is the element in Period 3 which has the same group with lithium? [Ans: Sodium / Na] 9. What is the element in Period 2 which has the same group with sulphur? [Ans: Oxygen / O] S3 Second Term Uniform Test Revision Guidelines 10 Term 1 Notes 2.2 1. Is nitrogen a metal, a non-metal or a semi-metal? [Ans: non-metal] 2. Is sulphur a metal, a non-metal or a semi-metal? [Ans: non-metal] 3. Is aluminium a metal, a non-metal or a semi-metal? [Ans: metal] 4. Is silicon a metal, a non-metal or a semi-metal? [Ans: semi-metal] Term 1 Notes 2.3 1. (a) Write the electronic arrangement of a calcium atom (Ca). [Ans: 2, 8, 8, 2] (b) Explain whether calcium atom (Ca) is stable. [Ans: It is unstable. It does not have a noble gases’ electronic arrangement.] 2. (a) Write the electronic arrangement of a chloride ion (Cl-). [Ans: 2, 8, 8] (Note: Cl = 2, 8, 7; Cl- = 2, 8, 8 as Cl accepts 1 extra electron) (b) Explain whether chloride ion (Cl-) is stable. [Ans: It is stable. It has a noble gases’ electronic arrangement.] 3. (a) Write the electronic arrangement of S2-. [Ans: 2, 8, 8] (Note: S = 2, 8, 6; S2- = 2, 8, 8 as S accepts 2 extra electrons) (b) Explain whether S2- is stable. [Ans: It is stable. It has a noble gases’ electronic arrangement.] S3 Second Term Uniform Test Revision Guidelines 11 Term 1 Notes 3.1 1. Draw the electronic diagram of C, showing electrons in all electron shells. ⤬ ⤬ C ⤬ ⤬ ⤬ [Ans: ] ⤬ 2. Draw the electronic diagram of Ar, showing electrons in all electron shells. ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ ⤬ Ar ⤬ ⤬⤬ [Ans: ⤬⤬ ] Term 1 Notes 3.2 1. Write the formula of the ions most likely formed by the given element. Element Ions likely to be formed Li [Ans: Li+] O [Ans: O2-] Cl [Ans: Cl-] 2+ Ca [Ans: Ca ] Term 1 Notes 3.3 2+ 2- 1. What is the chemical formula for the ionic compound formed by Cu and O ? [Ans: CuO] 2. What is the chemical formula for the ionic compound formed by Mg2+ and Cl-? [Ans: MgCl2] S3 Second Term Uniform Test Revision Guidelines 12 Term 1 Notes 3.4 1. Complete the following table. Substance Structural formula Number of bonds CH4 H H C H [Ans: 4 single bonds] [Ans: H ] O2 [Ans: O O] [Ans: 1 double bonds] PCl3 Cl [Ans: Cl P Cl ] [Ans: 3 single bonds] NOCl [Ans: O N Cl ] [Ans: 1 single bond + 1 double bond] H2O2 [Ans: H O O H] [Ans: 3 single bonds] 2. Draw the electronic diagram for the following substances. Structural formula Electronic diagram ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ F F F F [Ans: ⤬⤬ ⤬⤬ ] ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ ⤬⤬ Cl O H Cl O H [Ans: ⤬⤬ ⤬⤬ ] ⤬⤬ ⤬⤬ ⤬⤬⤬⤬ ⤬⤬⤬⤬ O C O O C O [Ans: ⤬⤬ ⤬⤬ ] S3 Second Term Uniform Test Revision Guidelines 13 Term 2 Notes 0.1 1. Which of following terms best describes the sample? A. Element B. Compound C. Mixture of elements D. Mixture of compounds [Ans: A] 2. Which of following terms best describes the sample? A. Element B. Compound C. Mixture of elements D. Mixture of compounds [Ans: D] 3. Which of following terms best describes the sample? A. Element B. Compound C. Mixture of elements D. Mixture of compounds [Ans: B] 4. How many atoms in a CH4 molecule? [Ans: 5] 5. How many atoms and kinds of atom in a H2O2 molecule? [Ans: 4 atoms, 2 kinds of atom] 6. How many atoms and kinds of atom in a KMnO4? [Ans: 6 atoms, 3 kinds of atom] S3 Second Term Uniform Test Revision Guidelines 14 Term 2 Notes 1.1 1. What is the natural source of argon? [Ans: air] 2. What is the natural source of oxygen? [Ans: air] 3. What is the method of extraction to get argon? [Ans: Fractional distillation of liquid air] 4. What is the natural source of nitrogen? [Ans: Fractional distillation of liquid air] Term 2 Notes 2.1 1. What is the natural source of sodium hydroxide? [Ans: sea water] 2. What is the natural source of hydrogen? [Ans: sea water] 3. What is the method of extraction to get sodium hydroxide? [Ans: Electrolysis of sea water] 4. What is the natural source of chlorine? [Ans: Electrolysis of sea water] 5. What is the most abundant substance in sea water? [Ans: water / H2O] 6. What is the most abundant compound in sea water? [Ans: water / H2O] 7. What is the most abundant salt in sea water? [Ans: sodium chloride / NaCl] S3 Second Term Uniform Test Revision Guidelines 15 Term 2 Notes 2.2 1. What is the acid used to clean the wire in a flame test. [Ans: concentrated HCl] 2. Should we use a luminous or a non-luminous flame in a flame test? [Ans: non-luminous flame] 3. Suggest a chemical method to distinguish KCl and CaCl2. [Ans: Perform a flame test to each of them. KCl will show a lilac flame while CaCl2 will show a brick red flame.] 4. Suggest a chemical method to distinguish copper(II) sulphate and potassium sulphate. [Ans: Perform a flame test to each of them. Copper(II) sulphate will show a bluish green flame while potassium sulphate will show a lilac flame.] Term 2 Notes 3.1 1. Quicklime is the common name of A. CaO. B. Ca(OH)2. C. CaCO3. D. Ca(HCO3)2. [Ans: A] 2. Limewater is the common name of A. CaO. B. Ca(OH)2. C. CaCO3. D. Ca(HCO3)2. [Ans: B] 3. The chemical formula of chalk is A. CaO. B. Ca(OH)2. C. CaCO3. D. Ca(HCO3)2. [Ans: C]