how has the modern periodic table been developed by scientists over the years?

How has the modern periodic table been developed by scientists over the years?

How has the modern periodic table been developed by scientists over the years?

John Dalton – arranged the elements in order of mass. John Newlands – ordered the elements in order of mass, but divided them up in

to groups of 8. This was because every 8th element had similar properties. Dmitri Mendeleev – developed the modern periodic table as we now know it. He

left gaps in the table where elements had not been discovered yet.

How properties do Group I metals have?

How properties do Group I metals have?

- Size of atom increases down the group- All elements have one outer electron- Reactivity increases DOWN the group.

- Reactivity increases as the electrostatic forces are weaker and so the electron is more easily lost.

- React with oxygen to form oxides. - React with water to produce hydroxides and hydrogen gas.

- Known as the alkali metals.- Stored in oil because they are so reactive. - Shiny and soft – can be cut with a knife.

- Low melting and boiling points

How properties do Group VII metals have?

How properties do Group VII metals have?

- Size of atom increases down the group- All elements have SEVEN outer electron- Reactivity DECREASES DOWN the group.

- Reactivity decreases as the electrostatic forces are weaker (as the atom is bigger) and so the electron are harder to attract.

- React with water to produce acids.- Known as the halogens.

- Coloured vapours. - Low melting and boiling points

- Poisonous non-metals- Poor conductors of energy and electricity- Form 1- ions when they gain an electron

- Form covalent bonds to form compounds, e.g. HCl- Can carry out displacement reactions between each halogen where a more reactive halogen replaces

a less reactive one.

Complete the equations – REMEMBER TO BALANCE THEM:

Na + H2O

K + H2O

Li + O2

Complete the equations – REMEMBER TO BALANCE THEM:

2Na + 2H2O 2NaOH + H2

2K + 2H2O 2KOH + H2

2Li + O2 2LiO

Where are the transition metals found and what are their key properties?

Where are the transition metals found and what are their key properties?

- Found in the large block in the centre of the periodic table. - They are good conductors of electricity and heat

- Hard and strong- High densities

- High melting points (except mercury) - Less reactive than Group I (don’t react with oxygen of water as easily)

- They form coloured compounds, e.g. copper sulphate is blue. - Can form more than one ion, e.g. Iron forms Fe2+ (green) and Fe3+ (reddish)

- Used as catalysts in industry, e.g Nickel for margarine manufacture.

What is the difference between hard and soft water and how can you tell?

What is the difference between hard and soft water and how can you tell?

- Hard water is water with Magnesium and Calcium ions dissolved in it- Hard water does not lather with soap

- Hard water form scum when reacts with soap- Soft water – no Mg or Ca

- Soft water – lathers with soap

What are the advantages and disadvantages of hard water?

What are the advantages and disadvantages of hard water?

Advantages – health as Ca is good for strong teeth, Mg for heart disease

Disadvantages – doesn’t form lather and so not hard to clean self,

expensive as need more soap to clean things, form scale when heated so blocks pipes,

scale forms on heating elements in kettles and makes it a poor conductor so costs more to heat water.

How is hard water formed?

How is hard water formed?

As water flows through rivers the Magnesium ions and Calcium ions in rocks dissolves in the water.

Give examples of rocks that contribute to hard water

Give examples of rocks that contribute to hard water

Gypsum – Calcium Limestone – Calcium

Limestone is virtually insoluble in water. How are caves formed in this rock?

Limestone is virtually insoluble in water. How are caves formed in this rock?

Carbon dioxide dissolves in rain waterThis makes the rain water acidicThis reacts with the limestone

Calcium ions are released that then dissolve in the water making hard water.

What is the difference between temporary and permanent hard water?

What is the difference between temporary and permanent hard water?

Temporary hard water is water that can be made soft by boiling.

Permanent hard water is water is not made soft by boiling. Although, it can be made soft by other means.

How can permanent hard water be softened?

How can permanent hard water be softened?

Add washing soda (sodium carbonate) – this allows the Ca and Mg ions to be precipitated out.

Ion-Exchange column – a column containing resin packed with sodium ions. The sodium ions exchange with the Ca and Mg ions and make it soft.

How does an ion-exchange column become recharged AND why is this not the best method?

How does an ion-exchange column become recharged AND why is this not the best method?

Wash with salt (sodium chloride) solution.Water produced contains Na ions which are linked to heart disease.

What is water used for?

What is water used for?

We use water for:

Industry – raw material, solvent, coolantHome – drinking, washing, cleaning

Where do we get our drinking water from?

Where do we get our drinking water from?

1. Boreholes – these are safe as the water is filtered through rocks. We just need to sterilise (kill the microbes) by adding chlorine.

2. Rivers/reservoirs - treatment needed.

What is found inside a water filter cartridge found used in a water jug in the home?

What is found inside a water filter cartridge found used in a water jug in the home?

Substance Reason Problem

Activated Carbon Reduces the amount of chlorine, pesticides, organic

impurities.

Ion exchange resin Reacts to remove Mg and Ca ions.

Replaces it with Na ions which are not good for the heart.

Silver Discourage bacteria growth. Expensive

Is our drinking water pure? If not, how do we purify it?

Is our drinking water pure? If not, how do we purify it?

Is it Pure?

No – as there are still dissolved substances in the water.

So, how do you get pure?

You distil the water by boiling it, producing steam and then cooling it.

Problem: Expensive as requires energy to heat the water.

What is added to our drinking water, and why?

What is added to our drinking water, and why?

Substance Added Reason Debate

Chlorine Sterilise – kill bacteria (added to sewage to clean it)

Reacts with organic substances to produce toxic products.

(need lots)

Fluoride Reduced teeth decay. Pros/Cons

What is the definition of the following terms?

Term Definition

Exothermic

Endothermic

Combustion

Joule

Kilojoule

Calorie

Mole

Relative molecular mass

What is the definition of the following terms?

Term Definition

Exothermic A reaction that GIVES OUT energy to the surroundings

Endothermic A reaction that TAKES IN energy from the surroundings.

Combustion Where a substance burns in oxygen.

Joule The unit of energy

Kilojoule 1000J

Calorie The amount of energy needed to raise 1kg by 1C

Mole The amount of substance in the relative atomic/formula mass of a substance in grams

Relative molecular mass

The total of the relative atomic masses, added up in the ration shown in the chemical formula, for a substance.

What is the equation and unit for calculating the energy released from a fuel?

What is the equation and unit for calculating the energy released from a fuel?

Calorimeter allows you to compare energy (metal can with water in it). Equation:

Q = mc∆TQ = Energy releasedm = Mass of water heated (1cm3 = 1g)c = Specific heat capacity (Energy needed to raise 1g by 1C)∆T = Change in temperatureFor water its specific heat capacity (c) is 4.2J/gC

How does an energy graph vary for an exothermic and endothermic reaction?

How does an energy graph vary for an exothermic and endothermic reaction?

What is meant by activation energy and how does an enzyme affect it?

What is meant by activation energy and how does an enzyme affect it?

In a chemical reaction, what is energy needed for AND when is energy released?

In a chemical reaction, what is energy needed for AND when is energy released?

For a chemical reaction to take place there needs to be BONDS BEING BROKEN and BONDS BEING FORMED.

To break a bond = ENERGY NEEDS TO BE SUPPLIED. To form a bond = ENERGY IS GIVEN OUT.

In the following reaction, what bonds are broken and formed?

2H2 + O2 2H2O

In the following reaction, what bonds are broken and formed?

2H2 + O2 2H2O

What are the advantages and disadvantages of using hydrogen as an alternative fuel?

What are the advantages and disadvantages of using hydrogen as an alternative fuel?

In terms of bon energies, how can you tell an exothermic from an endothermic reaction?

In terms of bon energies, how can you tell an exothermic from an endothermic reaction?

Bond Breaking Bond Forming Type of Reaction

Less energy needed More energy needed Exothermic

More energy needed Less energy needed Endothermic

For the following reaction, work out the energy released

N2 + 3H2 2NH3

Bond Bond Energy (kJ/mol)

Bond Bond Energy (kJ/mol)

C-C 347 H-Cl 432

C-O 358 H-O 464

C-H 413 H-N 391

C-N 286 H-H 436

C-Cl 346 O=O 498

Cl-Cl 243 N≡N 945

For the following reaction, work out the energy released

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

1 x N≡N 3 x H-H 6 x N-H

Bond Energy 945 3 x 436 6 x 391

Total = 2253 = 2346