SPM Chemistry Form 4 Notes

SPM Chemistry Form 4 Notes – Chemical Bonds

(Part 1)

Formation of Compounds

 Compounds – different elements that chemically bonded together

 Octet electron arrangement – electron arrangement of an atom where the outermost occupied shell is filled with eight valence electrons

 Duplet electron arrangement – electron arrangement of an atom where a single shell filled with two valence electrons

Example:

Compound water is hydrogen and oxygen atoms are chemically bonded together.

Stability of Noble Gases

 Atom of noble gas does not gain, lose nor share electrons with other atoms.

 Noble gas atoms do not combine with atoms of other elements to form compounds or with each other to form molecules.

 Noble gases are chemically unreactive.

 Noble gases exist as monoatomic. Chemical Bonds

Chemical Bond

Types of chemical bonds:

 ionic bonds (metal + non-metal)

Atoms of other elements can achieve the stable octet electron arrangement by  transfer of electrons

Scientist

Italian physicist Amedeo Avogadro (Name at birth: Lorenzo Romano Amedeo Carlo Avogadro)

 Born: 9 August 1776

 Birthplace: Turin, Piedmont, Italy

 Died: 9 July 1856

 Best Known As: The guy they named Avogadro’s number after

1. Avogadro constant / Avogadro’s number is 6.02 x 1023 2. Atomic substances

 Elements – all the particles are atoms.

 Example: zinc (Zn), sodium (Na), aluminium (Al) and all noble gases, argon (Ar), helium (He) and neon (Ne).

 RAM (Relative Atomic Mass) of Na = 23 3. Molecular substances

 Covalent compounds – the particles are molecules.

 Example: carbon dioxide (CO2), water (H2O) and non-metal elements, iodine (I2),

nitrogen (N2) and oxygen (O2).

 RMM (Relative Molecular Mass) of I2 = 127 + 127 = 254

4. Ionic substances

 Ionic compounds – the particles are ions.

 Example: sodium chloride (NaCl), hydrochloric acid (HCl) and potassium iodide (KI).

 RFM (Relative Formula Mass) of HCl = 1 + 35.5 = 36.5

5. Avogadro’s Law / Gas Law states that equal volumes of all gases contain the same number of molecules under the same temperature and pressure.

 Example: equal volumes of molecular hydrogen and nitrogen would contain the same number of molecules under the same temperature and pressure.

6. Volume of gas (dm3) = Number of moles of gas x Molar volume

7. Room temperature and pressure (r.t.p.) = 24 dm3 mol-1 (25°C and 1 atm)  Example: What is the volume of 5.0 mol helium gas at s.t.p.?

 Volume of gas = Number of moles x Molar gas volume = 5.0 mol x 24 dm3 mol-1

= 120 dm3

 Example: What is the volume of 5.0 mol helium gas at s.t.p.?  Volume of gas = Number of moles x Molar gas volume

= 5.0 mol x 22.4 dm3 mol-1 = 112 dm3

9. Mass (g) = Number of moles x Molar mass

10. Number of particles = Number of moles x Avogadro constant 11. Volume (dm3) = Number of moles x Molar volume

Be sure to copy down all these formulae a few times on paper so that you will have a better chance recalling it in the future. Copying them onto a card to bring around will be very helpful.

Empirical and Molecular Formulae

1. Empirical (simplest ratio of atoms of each element that present in the compound) and molecular formulae (actual number of atoms of each element that are present in one molecule of the compound) indicate:

 the types of the elements

 the symbols of the elements and the ratio of atoms or  moles of atoms of each element in a compound. 2. Molecular formula = (empirical formula)n

n is a positive number

Compound Molecular formula n Empirical formula

Carbon dioxide CO2 1 (CO2) = CO2

Ethane CH3 2 (CH3)2 = C2H6

Propene CH2 3 (CH2)3 = C3H6

Glucose CH2O 6 (CH2O)6 = C6H12O6

Quinine C10H12NO 2 C20H24N2O2

3. Chemical formulae for covalent compounds.

Name Chemical

formula

Number of each element

Oxygen gas O2 2 oxygen atoms

Ammonia NH3 1 nitrogen atom and 3

hydrogen atoms

Water H2O 2 hydrogen atoms and 1

oxygen atom 4. Cations are positively-charged ions.

Charge Cations Formula

+1 Ammonium ion NH4+ +1 * Copper(I) ion Cu+ +1 Hydrogen ion H+ +1 Lithium ion Li+ +1 * Nickel(I) ion Ni+ +1 Potassium ion K+ +1 Silver ion Ag+ +1 Sodium ion Na+ +2 Barium ion Ba2+ +2 Calcium ion Ca2+ +2 * Copper(II) ion Cu2+ +2 * Iron(II) ion Fe2+ +2 * Lead(II) ion Pb2+ +2 Magnesium ion Mg2+ +2 * Manganese(II) ion Mn2+ +2 Nickel(II) ion Ni2+ +2 * Tin(II) ion Sn2+ +2 Zinc ion Zn2+ +3 Aluminium ion Al3+ +3 * Chromium(III) ion Cr3+ +3 * Iron(III) ion Fe3+ +4 * Lead(IV) ion Pb4+ +4 * Tin(IV) ion Sn4+

* refer to the Roman numerals

5. Anions are negatively-charged ions.

Charge Anions Formula

-1 Bromide ion Br

--1 Chloride ion Cl

--1 Chlorate(V) ion ClO3

--1 Ethanoate ion CH3COO

--1 Fluoride ion F

--1 Hydride ion H

--1 Hydroxide ion OH

--1 Manganate(VII) ion MnO4

--1 Nitrate ion NO3

--1 Nitrite ion NO2

--2 Oxide ion O

2--2 Carbonate ion CO3

2--2 Chromate(VI) ion CrO4

2--2 Dichromate(VI) ion Cr2O7 2--2 Sulphide ion S 2--2 Sulphate ion SO4 2--2 Sulphite ion SO3 2--2 Thiosulphate ion S2O3 2--3 Nitride ion N 3--3 Phosphate ion PO4 3--3 Phosphite ion PO3

3-6. Chemical formulae for ionic compounds

Name Chemical formula Number of

cation

Number of anion

Zinc chloride ZnCl2 1 Zn2+ 2 Cl

-Copper(II) sulphate CuSO4 2 Cu2+ 2 SO4

2-Aluminium sulphate Al2(SO4)3 2 Al3+ 3 SO4

2-7. Meaning of prefixes Prefix Meaning Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10

8. Naming of chemical (non-metal) compounds with Greek numerical prefixes. Non-metal compound Chemical formula

Carbon monoxide CO Carbon dioxide CO2 Sulphur dioxide SO2 Sulphur trioxide SO3 Carbon tetrachloride (tetrachloromethane) CCl4

So, do come back for more Chemistry Essential Notes. If it is not simplified to its essense, then it is not from Study Very Very Easy. Let us do the summarising while you understand the core before you master the whole topic. Do share out this site with your friends.

Chemical Equation

1. Importance of chemical equation:

The types of reactants; the physical conditions; the quantity of reactants and products and stated in moles.

nA + nB –> pC + pD

2. Reactants are written in the left side of the reaction and products are written in the right side of the reaction.

 Example 1:

Word equation: Sodium hydroxide + sulphuric acid –> sodium sulphate + water Chemical equation: NaOH + H2SO4 –> Na2SO4 + H2O

Balancing equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O

Complete chemical equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O

 Example 2:

Word equation: Aluminium + copper(II) oxide –> aluminium(III) oxide + copper Chemical equation: Al + CuO –> Al2O3 + Cu

Balancing equation: 2Al + 3CuO –> Al2O3 + 3Cu

Complete chemical equation: 2Al + 3CuO –> Al2O3 + 3Cu

 Example 3:

Word equation: Nitrogen + hydrogen <–> ammonia Chemical equation: N2 + H2 <–> NH3

Balancing equation: N2 + 3H2 <–> 2NH3

Complete chemical equation: N2 + 3H2 <–> 2NH3

3. Information obtainable from chemical equations.  i) mass of reactants

 ii) volume of reacting gas  iii) mass of products formed  iv) volume of gas produced  Example:

2 cm3 of lead (II) nitrate solution is added to excess of potassium iodide solution. How many molecules of potassium nitrate will be formed?

[Relative atomic mass: N, 14; O, 16; K, 39; I, 127; Pb, 207; Avogadro's constant: 6.02 x 1023 mol-1]

Step 1: Write a complete chemical equation.

 Pb(NO3)2(aq) + 2KI(aq) –> PbI2(s) + 2KNO3(aq)

 From the equation, 1 mole of Pb(NO3)2 reacts with 2 moles of KI formed 1 mole PbI2

of and 2 moles of KNO3.

Step 2: Convert to moles.

 No. of moles of Pb(NO3)2

= Mass of Pb(NO3)2 / Relative molecular mass

= 2 / [207 + 2(14 + 3 x 16)] = 6.04 x 10-3 mol

Step 3: Ratio of moles.

 Number of moles of KNO3/ Number of moles of Pb(NO3)2

= 2/1

 Number of moles of KNO3

= (2 x 6.04 x 10-3) / 1 = 12.08 x 10-3 mol

Step 4: Convert to the number of molecules of potassium nitrate.  Number of molecules of KNO3

= 12.08 x 10-3 x 6.02 x 1023 = 7.27 x 1021

Once you have completed all parts in this series, you would have mastered the most basic of knowledge in SPM Chemistry. So make sure all Readers understand the basics before moving on to more advance topics.

SPM Chemistry Form 4 Notes – Periodic Table of Elements (Part 1) Development of the Periodic Table

Periodic Table

A) Antoine Lavoisier (1743 – 1794) – French chemist  Elements were classified into 4 groups

 Limitation – some wrong information (light and heat were consider as elements B) Johann Dobereiner (1780 – 1849) – German chemist

 Elements were classified into groups named as triad (Triad Law – relationship between properties and atomic masses of the elements)

 Limitation – few elements were classified C) John Newlands (1837 – 1898) – British chemist

 Elements were arranged horizontally in ascending order of their atomic masses and each row consisted of 7 elements (Law of Octaves – same properties were repeated at every eight element)

 Limitation – obeyed by the first 17 elements only (from H to Ca) D) Lothar Meyer (1830 – 1895) – German chemist

 Properties of the elements were in a periodic pattern with their atomic masses  Similar chemical properties occupied the same relative positions on the curve E) Dmitri Mendeleev (1834 – 1907) – Russian chemist

 Elements were arranged in ascending order of their atomic masses  Elements with similar chemical properties were placed in a group  Gap for undiscovered elements

 Prediction: gallium, scandium and germanium (discover later)  Separate groups for certain elements: transition elements

 Meedeleev’s Periodic Table was used as a basis for the formation of the Periodic Table

F) H. J. G. Moseley (1887 – 1915) – British physicist

 Elements were arranged horizontally in ascending order – proton numbers  Elements with the same number valence electrons – same group

 18 vertical columns – Group 1, Group 2, until Group 18  Alkali metal – Group 1

 Alkaline earth metal – Group 2

 Transition elements – Group 3 to Group 12  Halogen – Group 17

 Noble gas – Group 18

 Horizontal row of the elements – period  Period 1 – 2 elements

 Period 2 and 3 – 8 elements  Period 4 and 5 – 18 elements  Period 6 – 32 elements  Period 7 – 27 elements

 Lantanides – proton numbers 58 to 71  Actinides – proton numbers 90 to 103  Elements (Group 1, 2 and 13) – metal  Transition elements (Group 3 to 12) – metal  Elements (Group 15, 16 and 17) – non-metal  Carbon and silicon (Group 14) – non-metal

The next part, Part 2 Notes on Periodic Table of Elements for SPM Chemistry students will focus on the relationship between electron arrangement of the atom of an element to

its group and period. It’s easy for a Form 5 student when they look back but rather difficult

for a Form 4 student. So Form 4 students need to pay full attention when your teacher is teaching this part, or you can always refer back to Berry Berry Easy for our notes