Topic 3: periodic table and energy

What’s a row of elements on the periodic table known as

A period

What’s a column of elements in the periodic table known as

A group

What do elements in the same group have in common

Similar properties

What are the 4 main blocks of the periodic table

S, p, d and f block

What’s the first ionisation energy

The energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions

what happens to the first ionisation energy across a period

It increases

What happens to the first ionisation energy down a group

It decreases

What factors affect the first ionisation energy

Atomic radius, nuclear charge and electron shielding

Why does the first ionisation energy decrease down a group

The atomic radius increases, electron shielding increases and so the attraction between the nucleus and outer electrons decreases

Why does the first ionisation energy increase across a period

Nuclear charge increases whilst atom radius and electron shielding remains constant increasing the attraction between the nucleus and outer electrons

Why is there a rapid decreases in ionisation energy between the last element in one period and the first element in the next period

The increased atomic radius and electron shielding outweighs the increased nuclear charge

Why do successive ionisation energies of an element increase

Because removing an electron from a positive ion is more difficult than a neutral atom, electron shielding decreases and the proton to electron ratio increases

What are examples of giant covalent substances

Graphite, diamond, graphene and silicon (IV) oxide

What’s the shape and bond angle of diamond

Tetrahedral and 109.5

How many covalent bonds does each carbon form in diamond

4

What’s the shape and bond angle of graphite

Hexagonal and 120

How many covalent bonds does each carbon form in graphite and graphene

3

Why can the layers of carbon slide over each other in graphite

Because the intermolecular forces are weak

What are common properties of metallic substances

High melting and boiling point, lack of solubility and good electrical conductivity

Which giant covalent substances conduct electricity

Graphite and graphene

What’s the trend in melting point across period 2 and 3

The melting point increases from group 1-4 but then a sharp decrease in melting point from group 4-5 as the bonding changes from metallic and covalent to simple molecular

What’s the most common reaction of group 2 elements

Redox reactions

What are elements in group 2 known as

Alkali earth metals

What block are group 2 elements in

S-block

What ions do group 2 elements form

2+

What type of agents are group 2 elements

Reducing agents

What happens to the reactivity of group 2 elements down the group

It increases

Why does the reactivity increase down group 2

The atomic radius increases allowing more electron shielding which decreases the nuclear attraction allowing cations to form more easily

What’s the reaction of group 2 metals with oxygen

2X + O2 → 2XO

What’s the reaction of group 2 metals and water

X + 2H2O → M(OH)2 + H2

What’s the reaction of group 2 metals with an acid (use HCl in the example)

X + 2HCl → XCl2 + H2

What solutions do group 2 oxides form when reacting with water

Alkaline solutions

how does the solubility of group 2 metals change down the group

It increases down group 2

How are group 2 compounds used in agriculture

Calcium hydroxide is soluble in water and so is used to neutralise acidic soil

What the use of group 2 compounds in medicine

Magnesium hydroxide is partially soluble in water and forms milk of magnesia which neutralises excess stomach acid

What’s the trend in the boiling point of the halogens

The boiling point increases down the group

How do halogens exist at room temperature

As diatomic molecules

What intermolecular forces form between the halogens

Weak London forces

Out of chlorine bromine and iodine which is the most reactive

Chlorine

What colour solution does chlorine form as a free halogen

Pale green (sometimes mistaken as colourless)

What colour solution does bromine from as a free halogen

Yellow solution

What colour solution does iodine form as a free halogen

Brown (may include black solid as well)

What type of agent are halogens

Oxidising agents

What does chlorine react with to form a disproportionation reaction

Water and cold, dilute aqueous alkali

Why is chlorine reacting with water useful

It cleans the water making it drinkable

What’s produced in the reaction of chlorine and water

Chloride (I) acid (HClO) and Hydrochloric acid (HCl)

What’s produced in the reaction of chlorine and aqueous sodium hydroxide

Sodium chloride, sodium chlorate and water

What’s a risk of using chlorine to treat water

Chlorinated hydrocarbons could be formed

How can halide ions be identified

By dissolving the solution in nitric acid and adding silver nitrate solution dropwise

Why is nitric acid used to identify halide ions

It reacts with carbonate ions to prevent false positive results

What colour is silver chloride precipitate

White

What colour is silver bromide precipitate

Cream

What colour is silver iodide precipitate

Yellow

What is the follow up test for halide ions

Dilute and then concentrated ammonia is added to the silver halide solution

What’s the solubility of silver chloride

It’s soluble in dilute ammonia

What’s the solubility of silver bromide

It’s soluble in concentrated ammonia

What’s the solubility of silver iodide

It’s not soluble in dilute or concentrated ammonia

What the test for carbonate ions

Add an equal amount of dilute hydrochloric acid and sodium carbonate to a test tube and add the sodium carbonate solution along with a delivery tube that connects to a test tube of limewater

What’s the positive test for a carbonate ion

CO2 forms which forms a white precipitate of calcium carbonate when bubbled through limewater (the limewater turns cloudy)

What’s the test for sulfates

Acidify the sample with dilute hydrochloride acid and then add a few drops of aqueous barium chloride or nitrate

What’s the positive test result for a sulfate

a white precipitate of barium sulphate/barium nitrate

What’s the test for ammonium ions

Reacting the solution with warm aqueous sodium hydroxide forming ammonia gas

What’s the positive result for ammonia

A pungent smelling gas or a gas that turns red litmus paper blue

What’s the total chemical energy inside a substance known as

Enthalpy

What’s an exothermic reaction

A reaction where the products have less energy than the reactants

What happens to the temperature of the environment and the energy of the system

The energy of the environment increases and the energy of the system decreases

What’s the enthalpy change of an exothermic reaction

Negative as the enthalpy decreases

What’s an endothermic reaction

A reaction where the products have more energy than the reactants

What happens to the temperature of the environment and energy of the sytem

The temperature of the environment decreases and the energy of the system increases

What’s the enthalpy change of an endothermic reaction

Positive because the enthalpy increases

What’s activation energy

The minimum amount of energy needed for reactant molecules to successfully collide and start a reaction

What’s the enthalpy change of a reaction

The energy difference from reactants to products

What type of retractions are combustion reactions

Exothermic reactions

What are the standard conditions (pressure temperature and state)

100kPa, 298K and each substance in its standard physical state

What’s the standard enthalpy change of formation

The enthalpy change when one mole of a compound up formed from its elements under standard conditions

What’s the standard enthalpy change of combustion

The enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions

What’s the standard enthalpy change of neutralisation

The enthalpy change when one mole of water is formed by reacting an acid and an alkali under standard conditions

What’s the standard enthalpy change of reaction

The enthalpy change when the reactants in the stochiometric equation react to give the products under standard conditions

What’s the enthalpy change of formation for an element in its standard state

Zero

How can a calorimeter be made

Using a polystyrene cup

What’s specific heat capacity

The energy needed to increase the temperature of 1g of a substance by 1 degree

What’s the specific heat capacity of water

4.18 j g-1 k-1

What’s the specific heat capacity equation

Heat energy = mass x specific heat capacity x change in temperature

What’s bond enthalpy

The amount of energy required top break one mole of a specific covalent bond in the gas phase

Why are average bond enthalpies used

Because bond energies are affected by other atoms in the molecule (their environment)

What type of reaction is bond breaking

Endothermic as energy is required to break bonds

What type of reactor is bond formation

Exothermic as energy is released making new bonds

What’s Hess’s law

That the enthalpy change from elements to products (direct route) is equal to the enthalpy change of elements forming reactants and then products (the indirect route)

What’s are the equations for Hess’s law

Reactants to products = elements to products - elements to reactants

Elements to products = elements to reactants + reactants to products

What’s the equation for the enthalpy change of formation

Enthalpy change = products - reactants

What’s the equation for the enthalpy change of combustion

Enthalpy change = reactants - products

What’s collision theory

The theory that for a chemical reaction to take place the particles need to collide with each other in the correct orientation and with enough energy

What’s collision frequency

The number of collisions per unit in time

What’s effect does activation energy have on collision frequency

If more particles have more than the activation energy collision frequency will increase

What’s the effect of increased concentration of a solution on collision frequency

Increasing concentration increases collision frequency

What effect does increasing pressure have on collision frequency (in gaseous solutions)

Increasing pressure reduces the area of space for molecules to move increasing collision frequency

What’s the rate of reaction equation

Rate of reaction = change in amount of reactants or products (mol dm-3) / time (seconds)

How can rate of reaction be calculated in a graph

Using a concentration-time graph

How can you work out the rate of reaction from a concentration-time graph

By drawing a tangent from the points plotted on the graph

What’s a catalyst

A substance that increases the rate of reaction by providing the particles with an alternative mechanism with a lower activation energy