# Topic: Ions

## Revision questions – Ions

2019-05-29T23:20:30+00:00Categories: Uncategorized||

## 1:19 understand how to deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

Electrons are found in a series of shells (or energy levels) around the nucleus of an atom.

Each energy level can only hold a certain number of electrons. Low energy levels are always filled up first.

Rules for working out the arrangement (configuration) of electrons:

Example – chlorine (Cl)

1) Use the periodic table to look up the atomic number. Chlorine’s atomic number (number of protons) is 17.

2) Remember the number of protons = number of electrons. Therefore chlorine has 17 electrons. 3) Arrange the electrons in levels (shells):

• 1st shell can hold a maximum of 2
• 2nd can hold a maximum of 8
• 3rd can also hold 8

Therefore the electron arrangement for chlorine (17 electrons in total) will be written as 2,8,7

4) Check to make sure that the electrons add up to the right number

The electron arrangement can also be draw in a diagram.

Electron arrangement for the first 20 elements: ## 1:22 understand how the electronic configuration of a main group element is related to its position in the Periodic Table

Elements in the same group have the same number of electrons in their outer shell.

This is why elements from the same group have similar properties.

## 1:23 Understand why elements in the same group of the Periodic Table have similar chemical properties

Elements in the same group of the periodic table have the same number of electrons in their outer shells, which means they have similar chemical properties.

## 1:25 write word equations and balanced chemical equations (including state symbols): for reactions studied in this specification and for unfamiliar reactions where suitable information is provided

Example:

Sodium (Na) reacts with water (H2O) to produce a solution of sodium hydroxide (NaOH) and hydrogen gas (H2).

Word equation:

sodium + water –> sodium hydroxide + hydrogen

Writing the chemical equation

A chemical equation represents what happens in terms of atoms in a chemical reaction.

Step 1: To write a chemical equation we need to know the chemical formulae of the substances.

Na + H2O –> NaOH + H2

Step 2: The next step is to balance the equation: write a large number before each compound so the number of atoms of each element on the left hand side (reactants) matches the number on the right (products). This large number is the amount of each compound or element.

During this balancing stage the actual formulas for each compound must not be changed. Only the number of each compound changes.

2Na + 2H2O –> 2NaOH + H2

If asked for an equation, the chemical equation must be given.

State symbols are used to show what physical state the reactants and products are in.

State symbolsPhysical state
(s)Solid
(l)Liquid
(g)Gas
(aq)Aqueous solution (dissolved in water)

Example:

A solid piece of sodium (Na) reacts with water (H2O) to produce a solution of sodium hydroxide (NaOH) and hydrogen gas (H2).

2Na(s) + 2H2O(l) –> 2NaOH(aq) + H2(g)

## 1:37 understand how ions are formed by electron loss or gain

Ions are electrically charged particles formed when atoms lose or gain electrons.

They have the same electronic structures as noble gases. Metal atoms form positive ions (cations). Non-metal atoms form negative ions (anions).

## What is an ion? – Tyler de Witt video

Knowing the answer to “What’s an ion?” is absolutely key to Chemistry.

If you aren’t sure what an ion is, or why the idea of ions is crucial to Chemistry, then you should watch this video:

2019-02-10T14:55:25+00:00Categories: Uncategorized|Tags: , |

## Dogs teach ionic versus covalent bonding – video

This should give you a ruff idea of what the difference is between ionic and covalent bonding.

2019-05-28T15:27:33+00:00Categories: Uncategorized||

## In an ion, the number of protons does not equal the number of electrons – Tyler de Witt video

In an electrically neutral ATOM, the number of electrons equals the number of protons.

However, an ION is an atom (or group of atoms) which has either gained or lost some electrons, so for an ION the number of electrons does not equal the number of protons.

This excellent Tyler de Witt video explains this clearly:

2019-02-10T14:04:01+00:00Categories: Uncategorized|Tags: , |

## 1:38a understand how to use the charges of these ions in ionic formulae: metals in Groups 1, 2 and 3, non-metals in Groups 5, 6 and 7, Ag⁺, Cu²⁺, Fe²⁺, Fe³⁺, Pb²⁺, Zn²⁺, hydrogen (H⁺), hydroxide (OH⁻), ammonium (NH₄⁺), carbonate (CO₃²⁻), nitrate (NO₃⁻), sulfate (SO₄²⁻)

When given this information of the following ions, it is possible to work out the formulae of ionic compounds which include these ions.

Name of IonFormulaCharge
SulfateSO42--2
CarbonateCO32--2
NitrateNO3--1
HydroxideOH--1
AmmoniumNH4++1
Silver ionAg++1
Zinc ionZn2++2

2019-05-23T15:44:30+00:00Categories: Uncategorized||

## 1:39 write formulae for compounds formed between the ions listed in 1:38

Writing the electron configuration of an atom allows you to work out the electron configuration of the ion and therefore the charge on the ion.

Examples:

Atom = Mg

Electron configuration = 2,8,2

remove the two electrons from the outer shell to achieve the same electron configuration as the nearest noble gas, Neon (Ne 2,8)

Ion = Mg2+

[2,8]2+

Atom = O

Electron configuration = 2,6

add two electrons to the outer shell to achieve the same electron configuration as the nearest noble gas, Neon (Ne 2,8)

Ion = O2-  [2,8]2-

## Writing ionic formulae – Tyler de Witt video

This excellent video from the lovely Tyler de Witt explains how to write the formula of an ionic compound:

2019-02-10T14:31:50+00:00Categories: Uncategorized||

## 1:40 draw dot-and-cross diagrams to show the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7 only outer electrons need be shown

Sodium chloride, NaCl Magnesium chloride, MgCl2 Potassium oxide, K2O Calcium oxide, CaO Aluminium oxide, Al2O3 Magnesium nitride, Mg3N2 ## 1:42 understand why compounds with giant ionic lattices have high melting and boiling points

Ionic compounds have high melting and boiling points because they have a giant structure with strong electrostatic forces between oppositely charged ions that require a lot of energy to break.

Giant 3D lattice of sodium chloride (NaCl) ## Ionic bonding – Tyler de Witt videos

These videos are a really good introduction to ionic bonding:

2019-02-10T14:36:34+00:00Categories: Uncategorized||
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Section 1: Principles of chemistry

a) States of matter

b) Atoms

c) Atomic structure

d) Relative formula masses and molar volumes of gases

e) Chemical formulae and chemical equations

f) Ionic compounds

g) Covalent substances

h) Metallic crystals

i) Electrolysis

Section 2: Chemistry of the elements

a) The Periodic Table

b) Group 1 elements: lithium, sodium and potassium

c) Group 7 elements: chlorine, bromine and iodine

d) Oxygen and oxides

e) Hydrogen and water

f) Reactivity series

g) Tests for ions and gases

Section 3: Organic chemistry

a) Introduction

b) Alkanes

c) Alkenes

d) Ethanol

Section 4: Physical chemistry

a) Acids, alkalis and salts

b) Energetics

c) Rates of reaction

d) Equilibria

Section 5: Chemistry in industry

a) Extraction and uses of metals

b) Crude oil

c) Synthetic polymers

d) The industrial manufacture of chemicals