[CHEM] Chapter 8 - Periodic Table

1 DARRELL ER (COPYRIGHTED) © TOPIC 8: PERIODIC TABLE DARRELL ER (COPYRIGHTED) ©

2 CHAPTER ANALYSIS THE ABOUT TIME EXAM WEIGHTAGE • Content heavy chapter • 3 key concepts • Usually tested along with ‘Atomic Structure’ & ‘Chemical Bonding’ • Highly tested on specifically ‘alkali metals’, ‘halogens’ & ‘noble gases’. • Medium overall weightage • Constitute to 4% of marks for past 5 year papers DARRELL ER (COPYRIGHTED) ©

3 PERIODIC TABLE & TRANSITION METALS ALKALI METALS HALOGENS NOBLE GASES KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

4 PERIODIC TABLE Trend across a period (left to right) - Number of protons increases - Atomic radius decreases - Metallic properties decreases Trends down a group (top to bottom) - Number of protons increases - Number of electron shells increases - Atomic radius increases - Metallic properties remain constant DARRELL ER (COPYRIGHTED) © Horizontal rows are known as periods. (Represent number of electron shells.) Vertical rows are known as groups. (Represent number of valence electrons.) The block of elements between Group II and Group III are called transition metals and they tend to have variable oxidation states.

5 PERIODIC TABLE ION FORMATION Metallic elements will form cations as they lose their valence electrons to form positively charged ions. For example, Group I elements like Sodium (Na) will form Na+ with charge +1. Non-metallic elements will form anions as they gain electrons to form negatively charged ions. For example, Group VII elements like chlorine (CI) will form CI- with charge of –1. DARRELL ER (COPYRIGHTED) © Group I II III IV V VI VII VIII Valence electro ns 1 2 3 4 5 6 7 8 Period II Li Be B C N O F Ne Ion Li+ Be2+ B3+ - N3- O2- F- - Period III Na Mg Al Si P S Cl Ar Ion Na+ Mg2+ Al3+ - P3- S2- Cl- -

6 TRANSITION METALS PHYSICAL PROPERTIES OF TRANSITION METALS Transition metals has high melting points and high densities due to the strong metallic bonds. They are good electrical and thermal conductors. Transition metals also form coloured compounds. CHEMICAL PROPERTIES OF TRANSITION METALS Transition metals has the ability to exhibit multiple oxidation states. Hence, they are frequently used as catalysts. For example, iron is used in the Haber process to produce ammonia, and nickel is used in making margarine through the process of adding hydrogen to vegetable oil (hydrogenation). DARRELL ER (COPYRIGHTED) © TRANSITION METALS Transition metals are found in between the Group II and Group III elements in the periodic table.

7 ALKALI METALS DARRELL ER (COPYRIGHTED) © GROUP I: ALKALI METALS Group I elements are called alkali metals as they react with water to give alkaline solutions. Name of element Melting points / °C Density / gcm-3 Lithium (Li) Sodium (Na) Potassium (K) Rubidium (Rb) Caesium (Cs) Francium (Fr) 180 98 63 39 28 27 (decreases down the group) 0.534 0.971 0.862 1.532 1.873 - (increases down the group) PHYSICAL PROPERTIES OF ALKALI METALS - Low melting points - Low densities, lithium, sodium and potassium can float on water - Good conductor of electricity & heat Densities of alkali metals generally increase down the group while melting points decrease down the group. This is due to the increase in atomic radius down the group. Chemical properties of alkali metals As they have only one valence electron in their outermost shell, they form ionic compounds, with their resulting ions of +1 charge. Reactivity of alkali metals increases down the group due to the extra electron shells and the nucleus is further away, which increases the ease of losing the valence electron. Metal Chloride Nitrate Carbon ate Sulfate Oxide Hydroxid e Lithium Sodium Potassium LiCl NaCl KCl LiNO3 NaNO3 KNO3 Li2CO3 Na2CO3 K2CO3 Li2SO4 Na2SO4 K2SO4 Li2O Na2O K2O LiOH NaOH KOH

8 HALOGENS DARRELL ER (COPYRIGHTED) © GROUP VII: THE HALOGENS Halogens usually exist as diatomic molecules. PHYSICAL PROPERTIES OF HALOGENS - Low melting and boiling points that has an increasing trend down the group - Densities of the halogens increase down the group - Dissolve sparingly in water (chlorine, bromine and iodine) generally, but soluble in organic solvents. - Does not conduct electricity due to a lack of mobile charge carriers CHEMICAL PROPERTIES OF HALOGENS Reactivity decreases down the group. The ease of gaining a valence electron decreases as the valence shell is further away from the nucleus, making it more difficult to attract an electron. DISPLACEMENT REACTION A more reactive halogen is able to displace a less reactive halogen from an aqueous solution of its ions. Cl2 (aq) + 2KBr (aq)  2KCl (aq) + Br2 (aq) The solution will turn reddish brown due to the aqueous bromine produced. Name of element State Colour Fluorine (F2) Chlorine (Cl2) Bromine (Br2) Iodine (I2) Astatine (At2) Gas Gas Liquid Solid Solid (increases down the group) Pale Yellow Green Yellow Reddish brown Black Black (increasing colour intensity)

9 NOBLE GAS DARRELL ER (COPYRIGHTED) © GROUP 0: THE NOBLE GASES All noble gases have a fully filled valence shell. Noble gases are unreactive and inert since they have a stable electronic configuration. They exist as mono-atomic particles (single atoms). PHYSICAL PROPERTIES OF NOBLE GASES - Do not conduct electricity (lack of charge carriers) - Very low melting and boiling points - Increasing melting and boiling points going down the group - Increasing densities of noble gases going down the group USE OF NOBLE GASES Name of element Melting points / °C Boiling points / °C State Helium (He) Neon (Ne) Argon (Ar) Krypton (Kr) Xenon (Xe) Radon (Rn) - -248 -189 -157 -111 -71 (increases down the group) -269 -246 -186 -153 -108 -62 (increases down the group) Gas Gas Gas Gas Gas Gas Element Application Reason Helium (He) Fill airships & hot air balloons Low density comparative to air Neon (Ne) Fill interior of neon light tubes Unreactive gas Argon (Ar) Fill light bulbs Unreactive gas

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