Question: What is the friendliest group of elements across the periodic table of elements?
Answer: The Halogen group.
Now you must be wondering why the Berry Berry Teacher, Miss Isabelle Wong calls it the friendliest group. For those who answered Halogen, congrats. This is due to Halogens typically occuring in pairs in natural conditions. As you would have guessed it, Part 4 of Berry Berry Easy notes on SPM Chemsitry Form 4 – Periodic Table of Elements is focused on halogens. We’ll be looking at the friendly and interesting group of Group 17 elements or Halogens such as Fluorine, Chlorine, Bromine, Iodine and Astatine. The usual suspects as we learn each group includes the general properties/nature of elements in the group, physical properties, chemical properties and safety precautions.
(Tips: You should draw out the diatomic molecules and their electron configurations so that you can better understand why they typically exist in the form of diatomic molecules. Try to also memorise the atomic size as they go down a group. Note whether if it is metallic or non-metallic. How about their oxidising abilities? If you can answer those and beyond, you would have mastered the basic knowledge on halogens.)
SPM Chemistry Form 4 Notes – Periodic Table of Elements (Part 4)
Group 17 elements
- Group 17 elements are known as halogens
- Exist as diatomic molecules (F2, Cl2, Br2, I2 and At2)
- Atomic radius (atomic size) – increases (going down the group)
- The outermost shell of the atoms (F, Cl, Br, I and At) have 7 valence electrons
- Good oxidising agents
- Very reactive – decreases (going down the group)
- Very electronegative – decreases (going down the group)
|Element||Electron arrangement of atom|
|Fluorine / F||2.7|
|Chlorine / Cl||2.8.7|
|Bromine / Br||18.104.22.168|
|Iodine / I||22.214.171.124.7|
|Astatine / At||126.96.36.199.18.7|
- Insulators of electricity
- Poor conductors of heat
- Low melting point and boiling point
- Melting point and boiling point increases (going down the group) – molecular size increases / forces of attraction between molecules become stronger & more heat energy is required to overcome the stronger forces of attraction (Van der Waals’ forces of attraction between molecules).
- Colour: F2 (pale yellow gas), Cl2 (greenish-yellow gas), Br2 (reddish-brown liquid), I2 (purplish-black solid) and At2 (black solid – rarest naturally occurring element and extremely radioactive)
- Low density
- Density of element increases (going down the group) – increase in atomic mass
- Chemically reactive
- Reactivity decreases (down the group) – how easily it can gain one (single) more valence electron to achieve stable (octet) electron arrangement
- React with water – produce two acids
- React with hot iron – produce brown solids iron(III) halides
- React with sodium hydroxide NaOH solution – produce water and two types of sodium salts (sodium halide and sodium halite(I))
- Poisonous gas
- Wear safety goggles and gloves
- Handle in the fume cupboard
The next part, Part 5 in this series of notes from Berry Berry Easy on the Periodic Table of Elements for SPM Chemistry Form 4 students will be focused on Elements in a period. Example will be given across Period 3 which will form your basis of understanding for changes that occur when element moves across a period.