SC17-19 Flashcards
What are group 1 metals known as?
Alkali metals
Name the elements in group 1?
- Lithium
- Sodium
- Potassium
- Rubidium
- Caesium
- Francium
How many outer electrons do group 1 metals have?
1
Name the physical properties of group 1 metals?
- They have low melting and boiling points (compared with other metals).
- They’re very soft - can be cut with a knife.
How reactive are group 1 metals?
- Very reactive.
- They readily lose their single outer electron to form a 1+ ion with a stable electronic structure.
- The more readily a metal loses it outer electrons, the more reactive it is. So group 1 metals are very reactive.
- As you go down group 1, the alkali metals get more reactive. The outer electron is more easily lost because its further from the nucleus.
So its less strongly attracted to the nucleus and less energy is needed to remove it.
What happens when an alkali metal reacts with water?
They react vigorously
They produce hydrogen gas and a hydroxide of the metal
The reactivity of the metals increases down the group
Lithium will move around on the surface and fizzy.
Sodium and potassium do the same but they also melt in the heat of the reaction
Potassium can even be ignited (lilac flame).
What happens when lithium reacts with water?
It fizzes, floats on the surface and moves around.
What happens when sodium reacts with water?
It floats of the surface, moves around, fizzes and melts into a ball.
What a happens when potassium reacts with water?
It floats on the surface, moves around, fizzes, melts and can ignite with a lilac flame.
What is produced when alkali metals are put in water?
Hydrogen gas.
What are group 7 elements known as?
Halogens
Name the elements in group 7
- Fluorine
- Chlorine
- Bromine
- Iodine
- Astatine
How many outer electrons do group 7 elements have?
7
What are the properties of halogens?
- All diatomic = found in pairs
- Don’t conduct electricity.
- Brittle when solid.
- Poisonous and smelly
Become darker in colour down the group.
What a happens to the melting and boiling points as you go down group 7?
Increases
How can you test for chlorine?
Using damp blue litmus paper
The chlorine will bleach the paper, turning it white.
What are group 7 at room temp?
- chlorine is a fairly reactive, poisonous, green gas
- bromine is a poisonous red-brown liquid, which gives off an orange vapour at room temp.
- iodine is a dark grey crystalline solid which gives off a purple vapour when heated.
What is formed when halogens react with some metals?
They form salts called metal halides.
Explain the reactivity in group 7
- Reactivity decreases going down group 7
- It only needs to gain one electron to form a 1- ion
- It’s harder to attract the extra electron to fill the outer shell when its further away from the nucleus.
What happens when halogens react with metals?
They will react vigorously with some metals to form salts called metal halides.
Halogens higher up in group 7 are more reactive because they can attract the outer electron of the metal more easily.
What is formed when halogens react with hydrogen?
They form hydrogen halides.
What happens when halogens react with hydrogen?
They can form hydrogen halides.
They are soluble and they can dissolve in water to form acidic solutions.
E.g - HCL from hydrochloric acid in water.
What is a displacement reaction?
It’s where a more reactive element ‘pushes out’ (displaces) a less reactive element from a compound.
Elements in group 7 take part in displacement reactions.
How do displacement reactions show reactivity trends?
If you see a colour change, then a reaction has happened, the darker the colour the more reactive it is.
If there is no colour change then there has been no reaction
What are group 0 elements known as?
Noble gases
Name the elements in group 0
- Helium
- Neon
- Argon
- Krypton
- Xenon
- Radon
Explain the features and structure of noble gases
They’re colourless at room temperature.
They’re monatomic - made up of single atoms.
They don’t react much because they have a full outer shell
They’re non-flammable
Name the everyday uses of noble gases
- Helium is uses in balloons and airships.
- Argon can be used in filament lamps to stop the hot filament burning away.
- Argon and helium can also be used to protect metals that are being welded.
Name the patterns in the properties of the noble gases
Boiling point, melting point and density all increase as you go down group 0.
What is the rate of reaction?
It’s a measure of how fast the reaction happens
What’s the equation for rate of reaction?
(Amount of reactant used/amount of product formed) / time.
How can the rate of a reaction be observed?
By measuring how quickly the reactants are used up or how quickly products are formed.
What are the different ways that rate of reaction of reaction can be measured?
Precipitation
Change in mass
The volume of gas given off.
What is activation energy?
The minimum amount of energy needed for a reaction to occur.
What is the collision theory?
Particles are constantly moving.
For a reaction to take place they must collide.
And must have the right amount of energy for the reaction to happen, (activation energy).
What affects the rate of reaction?
Temperature Concentration (Catalyst) Surface area Pressure of gases
How does temperature affect the rate of reaction?
Increasing the temperature increases the rate of reaction.
The reactant particles speed up and have more energy.
They therefore collide more often and more particles have enough energy to react when they collide.
How does concentration affect the rate of reaction?
Increasing the concentration of solutions increases the rate of reaction.
There are more reacting particles in the same volume so collisions occur more often.
How does surface area affect the rate of reaction?
Increasing the surface area to volume ratio, by decreasing the size of solid pieces while keeping the total volume of solid the same, increases the rate of reaction.
There is more surface for collisions to occur on, so collisions occur more often.
How does pressure of gases affect the rate of reaction?
Increasing the pressure of gases increases the rate of reaction.
The reactant particles are squeezed closer together so collisions occurs more often.
How does a catalyst affect the rate of reaction?
Increases the rate of reaction.
How do catalysts work?
By decreasing the activation energy needed for a reaction to occur.
They do this by providing an alternative reaction pathway that has a lower activation energy.
As a result more particles have at least the minimum amount of energy needed for a reaction to occur when the particles collide.
What is an exothermic reaction?
Energy is transferred from stores of energy in chemical bonds to the surroundings.
What is an endothermic reaction?
Energy is transferred from the surroundings to stores of energy in chemical bonds.
What happens to the temperature during endothermic and exothermic reactions?
Exothermic - increases
Endothermic - decreases
What are reaction profiles?
They show energy levels of the reactants and the products in a reaction.
How is the activation energy shown on a reaction profile?
It the difference between the reactants and the highest point of the curve.
What are some examples of exothermic reactions?
Respiration
Combustion (explosions)
What are some examples of endothermic reactions?
Photosynthesis
What happens to the bonds in a chemical reaction?
Old ones are broken.
New ones are formed.
What process is bond breaking?
Endothermic.
Energy must be supplied to break existing bonds.
What process is forming bonds?
Exothermic.
Energy is released when new bonds are formed.
What is the equation for overall energy change?
= energy required to break bond - energy released by forming bonds.
What does a positive energy change mean?
Endothermic reaction
What does a negative energy change mean?
Exothermic
