Y10 Chemistry - Reactions and the Periodic Table

Covers the types of reactions, atoms and its structure, and the periodic table at a year 10 level.

Composition (or synthesis) reaction definition

A chemical reaction in which two or more reactants join together to form a single product

OR the building up of compounds by combining simpler substances

Decomposition reaction definition

A chemical reaction in which a single reactant breaks down into two or more products

OR the breakdown of compounds to form simpler substances.

Single displacement reaction definition

A chemical reaction in which one element is substituted for another in a compound.

For example, A + BC → B + AC (where A and B were swapped)

Double displacement reaction definition

A chemical reaction, where two reactants are exchanged between one another to form new compounds.

For example, AB + CD → AD + CB (where B and D swapped between one another)

Chemical reaction definition

The rearrangements of elements to form new compounds.

Reactants → Products

Quantitative data definition

The information about quantities and is numerical

Qualitative data definition

Descriptive data

Indicators of a chemical reaction

• Temperature change

• Colour change (though this isn’t very reliable)

• Formation of precipitate (a solid that forms when two aqueous solutions are mixed together)

• Fizzing/bubbling = gas produced

State symbols

• (s) = solid

• (l) = liquid

• (aq) = aqueous

• (g) = gaseous/gas

Collision theory definition

The collision theory explains what is necessary for chemical reactions to occur.

What must the reactant particles do to form products?

• The reactant particles must collide with enough energy to overcome the energy barrier (successful collisions) in order to form products.

• Reactant particles must also collide with the correct orientation in order to form products.

Activation energy definition

The amount of energy needed for a chemical reaction to proceed

OR the minimum amount of energy that molecules need to possess to have fruitful collision and form products.

Endothermic reaction definition

• Reactions which absorb energy from the surroundings in the form of heat to form products

• “Endo” means “energy enters” or “energy absorbed”

• Heat is taken from the surroundings, meaning that the temperature of the surroundings will decrease (become colder)

Examples of endothermic reactions

Photosynthesis, evaporating liquids, melting ice, cooking

Exothermic reaction definition

• Reactions which releases energy from the surroundings in the form of light, electricity, or heat to form products

• “Exo” means “energy exits” or “energy released”

• Heat is released from the system into the environment, meaning that the temperature of the surroundings will increase (become hotter)

Examples of exothermic reactions

Burning a substance, respirations, explosions, ice forming

Reaction rate definition

The speed of a chemical reaction: the time it takes for the reactants to be converted to products

Slow rate of reaction definition

• Takes a long amount of time for the reactants to be converted into products.

• If the time was limited, there would be a small amount of reactants consumed and a small amount of products produced.

Fast rate of reaction definition

• Takes a short amount of time for the reactants to be converted into products.

• If the time was limited, there would be a high amount of reactants consumed and a high amount of products produced.

The factors that impact reaction rates

• Temperature

• Concentration

• Particle size or surface area

• Use of a catalyst

How temperature affects the reaction rate of a chemical reaction

If the temperature is increased, the particles have more energy (kinetic) and so they move quicker.

Increasing the temperature increases the rate of reaction because the particles collide more often (reference to collision theory) and with more energy.

For colder temperature, it slows.

How concentration of the reactants affects the reaction rate of a chemical reaction

Concentration: the number of reactant particles per unit volume

If the concentration of reactants is increased, there are more reactant particles moving together. There will be more collisions and so the reactant rate is increased.

The higher the concentration of reactants, the faster the rate of reaction will be.

How the surface area or particle size affects the reaction rate of a chemical reaction

By decreasing the particle size of a reactant, the surface area increases as well.

Only exposed particles at the surface are able to collide with other reactant particles.

Therefore, the greater the surface area, the higher the chance of collisions, thus the faster rate of reaction.

The smaller the particle size (the larger the surface area) the faster the reaction.

How the use of a catalyst affects the reaction rate of a chemical reaction

Catalysts speed up the rate of a reaction by providing an alternative reaction pathway that lowers the activation energy.

This allows for more particles to have greater than the activation energy leading to more successful collisions and a faster rate.

Catalysts lower how much energy is required for a chemical reaction.

A catalyst does not react in the chemical reaction itself.

The maximum number of electrons that can fill the first four shells of an atom

2, 8, 8, 2

Structure of an atom

• Protons and neutrons are located in the nucleus of an atom

• Electrons are located beyond the nucleus

Protons definition

A subatomic particle of an atom with a positive charge, located in the nucleus of an atom

Neutron definition

A subatomic particle of an atom with a neutral charge, located in the nucleus of an atom

Electron definition

A subatomic particle of an atom with a negative charge, located around and beyond the nucleus of an atom

Valence shell definition

The outmost electron shell of an atom

Characteristics of a neutral atom

An atom where the number of protons is equal to the number of electrons

The atomic number of an element (the number of protons)

The mass number of an element (The number of protons and neutrons)

Ion definition

Ions are atoms which contain an uneven number of protons and electrons which results in an overall positive or negative charge.

The two types of ions

• Cations (+)

• Anions (-)

Cation definition

Cations are atoms which contain more protons than electrons, resulting in an overall positive charge.

Anion definition

Anions are atoms which contain more electrons than protons, resulting in an overall negative charge.

How do you show that the atom is an ion is word and symbol format?

• Add the word ‘ion’ after the name of the element

• On symbol format, add the number with either the positive or negative symbol based on the difference between the ions’ electrons and protons (strictly in that order)

• Example1: Phosphorus ion with 18 electrons and 15 protons; P^3- (anion)

• Example2: Calcium ion with 18 electrons and 20 protons; Ca²⁺ (cation)

Isotope definition

Atoms with the same number of protons but with different numbers of neutrons, therefore having a different mass number

‘Valence’ definition

The outer-most

Shells definition

The major energy levels in an atom

Shell symbols

K(1), L(3), M(5), N(7)

Orbitals definition

The electrons which occupy the three-dimensional space around the nucleus

Subshell symbols

s, p, d, f

Periods in the Periodic Table definition

The horizontal rows (ranging from 1-7)

Period number suggestion about the element

The number of electron shells

Groups in the Periodic Table definition

The vertical columns (ranging from 1-18)

Group number suggestion about the element

The number of electrons in the valence shell

Atomic number suggestion about the element

Number of protons (which leads to number of electrons, in neutral atoms)

Metals location in the Periodic Table

The left side; lose electrons

Non-metals location in the Periodic Table

The right side; gain electrons

Metalloids location in the Periodic Table

Share metal and non-metal properties

Define Electronegativity

How strongly an atom attracts electrons towards itself.

• The greater the electronegativity, the greater the ability of the atom to attract electrons towards its nucleus.
  

• Metals have low electronegativity as they have only a few loosely held valence electrons
  For example: Na = 2.8.2 → the valence shell only as 1 electron, therefore its electronegativity is weaker.
  Non-metals have high electronegativity

Trend in Electronegativity Down a Group of a Periodic Table

• Decreases

• More shells are added down a group, therefore there will be less attractive force between valence electrons and the nucleus.

Trend in Electronegativity Across a Period of a Periodic Table

• Increases

• The number of protons increases across a period, therefore there will be a stronger attraction between the nucleus and valence electrons, pulling the shells closer to the nucleus.

Define Ionisation

The energy required to remove a valence electron from an atom.

• The greater the attraction between the valence shell and the nucleus, the more energy is required to remove the valence electrons from the atom.
  

• Atoms are able to lose their electrons to become ions.

Trend in Ionisation Energy Down a Group of the Periodic Table

• Decreasing

• As the number of electron shells increase as the periodic table progresses down a group, electrons get further away from the nucleus, therefore they are less tightly held and easy to remove.

Trend in Ionisation Energy Across a Period of the Periodic Table

• Increasing

• The number of protons increase across a period, it causes a greater attraction between valence electrons and the nucleus, therefore it is harder to remove from the atom.

Present elements in metallic bonding

Metals

Present elements in covalent bonding

Non-metals

Present elements in ionic bonding

Metal and non-metals

Properties of metals (4)

• Good conductors of heat and electricity

• Malleable - can be moulded into different shapes

• Ductile - can be stretch into a wire

• Lustrous - can reflect light (shiny)

Properties of non-metals (3)

• Poor conductors of heat and conductivity

• The ones that undergo covalent bonding are mostly in a gas form so ae neither malleable or brittle or lustrous

• Have relatively low melting points are they have relatively weak intermolecular forces of attraction between molecules

Why metals are malleable and ductile

Cations can roll over one another whilst the electrons keep them close together

Why non-metals are poor conductors of heat and electricity

No free moving electrons to carry a charge

Metals have low…

ionisation energy, meaning that they easily lose electrons = cation

Non-metals and high…

electronegativity, meaning they have strong ability to attract electrons, gaining lots = anion

Draw a labelled diagram of an ionic lattice as a solid

Draw a labelled diag