Non-metal Elements Overview

25min Part 3 / Ch5 / Lesson 1

Prerequisites: 1-1-5

Objectives

Describe properties and reactions of Group 17 (halogens)
Understand properties of Group 16 elements (oxygen, sulfur) and their compounds
Know basic properties of Group 15 elements (nitrogen, phosphorus)

Halogens (Group 17)

Halogens: F₂, Cl₂, Br₂, I₂

All are diatomic molecules, colored, and toxic
Reactivity decreases down the group; melting/boiling points increase
Strong oxidizing agents (F₂ is the strongest)

Element	Formula	Color	State at room temp	Oxidizing power
F	F₂	Pale yellow	Gas	Strongest
Cl	Cl₂	Yellow-green	Gas	Strong
Br	Br₂	Red-brown	Liquid	Moderate
I	I₂	Dark purple	Solid	Weak

Properties of halogens

Hydrogen halides: HF, HCl, HBr, HI

Only HF is a weak acid (the rest are strong acids)
HF etches glass (reacts with $\mathrm{SiO_2}$ )

Oxygen and Sulfur (Group 16)

Allotropes of oxygen: $\mathrm{O_2}$ (oxygen) and $\mathrm{O_3}$ (ozone)

Allotropes of sulfur: rhombic sulfur $\mathrm{S_8}$ , monoclinic sulfur, plastic sulfur

Sulfuric acid $\mathrm{H_2SO_4}$ properties:

Concentrated: non-volatile, dehydrating, hygroscopic; hot concentrated H₂SO₄ is an oxidizer
Dilute: behaves as a strong acid (neutralization, reacts with metals to release H₂)

Nitrogen (Group 15)

$\mathrm{N_2}$ : very stable (triple bond N≡N)
Ammonia $\mathrm{NH_3}$ : dissolves in water to give a weak base
Nitric acid $\mathrm{HNO_3}$ : strong acid with oxidizing ability

Check Your Understanding

Q1 Which halogen has the strongest oxidizing power?

Q2 Which hydrogen halide is the only weak acid?

Q3 Which is NOT a property of concentrated sulfuric acid?

Exercises

Q1. Write the equation for passing chlorine gas through potassium bromide solution, and explain why this reaction occurs.

Solution

$\mathrm{Cl_2 + 2KBr \rightarrow 2KCl + Br_2}$

Chlorine ( $\mathrm{Cl_2}$ ) has stronger oxidizing power than bromine ( $\mathrm{Br_2}$ ), so it takes electrons from $\mathrm{Br^-}$ ions, liberating $\mathrm{Br_2}$ . In general, a more reactive halogen displaces a less reactive one: F₂ > Cl₂ > Br₂ > I₂.