Year 10 Chemistry Unit 1

Patterns in groups

• no. valence electrons

• no. shells increasing by 1 each time

Patterns in periods

• no. shells

• electrons increase by 1

• protons increase by 1

• valence electrons increase by 1

What elements do periodic table patterns count for

All elements except transition metals

Group 1 pattern

• 1 valence electron

• alkali metals

Group 2 Pattern

• 2 valence electrons

• alkali earth metals

Group 13 pattern

• 3 valence electrons

Group 15 pattern

• 5 valence electrons

Group 16 patterns

• 6 valence electrons

Group 17 pattern

• 7 valence electrons

• Halogens

Group 18

• Full outer shell

• noble gases

Proton mass

1

Neutron mass

1

Electron mass

almost 0

Proton charge

+1

neutron charge

0

electron charge

-1

Periods

Horizontal rows

Groups

Vertical columns

Isotopes

• Atoms with the same number of protons but a different number of neutrons

• Atoms of the same element with different mass numbers

relative Atomic mass / average atomic mass

average of the atomic masses of all the different isotopes in a sample

Relative atomic mass formula

(%1xAM2)/100 + (%2xAM2)/100 + …

Ion

Atom of an element that has gained or lost electrons (no longer neutral) - has a positive or negative charge

Positive Ion

• Cation

• Atom has more protons than electrons

• Atom loses an electron

• Positive net charge

Negative Ion

• Anion

• Atom Gains an electron

• More electrons than protons

• Negative net charge

Valence electrons

Electrons in the outermost shell of an atom

Elements forming anions and cations

Metals form cations, non-metals form anions

Chemical Reaction

A process in which one or more substances are converted to one or more different substances

Open System

Has external interactions, molecules and energy can both move in and out

Closed System

Molecules cannot move in and out but heat can still be transferred

Isolated System

No transfer of molecules or energy

Law of Conservation of Mass

Mass is neither created nor destroyed, mass is conserved from reactants to products

Law of Conservation of mass formula

Mass(reactants)=Mass(products)

Avogadro’s number

6.022×10²3 atoms

Molar Mass

equal to the atomic mass of each substance

Moles formula

Moles(n)=mass(g)/molecular mass (gmol^-1)

Molarity

number of moles of solute per litre of solution

Molarity formula

C(mol/L)=N(mole)/V(L)

Ionic bonding

Complete transfer of valence electrons between atoms, occurring between metals and nonmetals.

Polyatomic ions

• do not change name

• group of atoms considered to behave as a single unit

• has a net charge

1

mono

2

Di

3

tri

4

tetra

5

penta

6

hexa

7

hepta

8

octa

9

nona

10

deca

covalent bonding

Bonding occurring between two non-metal ions. ions share electrons to obtain a full outer shell

Diatomic elements - definition

Elements appearing in pairs and exist as gases at room temperature

Diatomic Elements - Elements

• Hydrogen

• Nitrogen

• Oxygen

• Fluorine

• Chlorine

• Bromine 

• Iodine

What is needed for a chemical reaction

particles collide with enough energy and the right orientation

Collision theory

• reactant particles must collide in order to react

• there must be minimum energy in the collision

• colliding particles must be correctly orientated

Kinetic theory

Degree to which particles move

Activation Energy

the minimum amount of energy needed for the particles to react

What does reaction rate depend on

• frequency of collision between two particles

• energy which particles collide

Factors affecting reaction rate

• increased concentration of dissolved reactants

• increased pressure of gaseous reactants

• increased surface area of solid reactants

• use of a catalyst

• increased temperature

Why does concentration affect reaction rate

more particles in the same amount of space, particles are most likely to collide and react

why does surface area affect reaction rate

• reactions involving a solid take place at the surface

• if the solid is split, surface area increases

• increased area for reactant particles to collide with

Effect of temperature on reaction rate

• higher temperature: more energy

• move faster and more likely to collide with other particles

How to measure rate of reaction

change in the mass of a reactant or product in a specific amount of time.

speed of reactions

• reactions do not proceed at steady rates and deaccelerate until they stop

• as reaction progresses, reaction concentration decreases - frequency of reactions decreases

calculating reaction rate from graphs

y/x, change in mass/change in time

catalyst

substance that speeds up a reaction, does not get used up, can be reused

Electron shielding

• electrons in inner shells shield valence electrons from the nucleus by reducing the attraction between the nucleus and electrons

• electrons in the outer shells are attracted to the positively charged nucleus but are also repelled by the negatively charged electrons in the inner shells

Electron shielding trend down a group

• increase

• more electron shells so there are more inner electrons blocking the nucleus’ pull on outer electrons

electron shielding trend across a period

• no change

• no new shells added, shell no. stays the same

electrostatic attraction

• attraction between electrons and protons where positive and negative charges are attracted

• holds electrons close to the nucleus

• plays role in forming ions and compounds

• strength of attraction depends on magnitude and distance of charges

Electrostatic attraction trend down a group

• decrease

• more shells, larger atomic radius, increased energy levels

Electrostatic attraction trend across a period

• increase

• number of energy levels doesn’t change, increase in protons resulting in electrons having greater attraction to nucleus.

Metal reactivity

metals react by losing electrons to form cations and reactivity depends on how easily atoms lose valence electrons

Metal reactivity trend down a group

• Increase

• More electron shielding, less electrostatic attraction, valence electrons lost more easily

Metal reactivity trend across a period

• decrease

• electrostatic attraction increases, protons increase, electrons are pulled closer and less likely to be removed

Nonmetal reactivity

nonmetals react by gaining electrons to form anions, reactivity depends on the level of electrostatic attraction

nonmetal reactivity trend going down a group

• decrease

• more shells, further away from nucleus

• more distance between electrons and protons, decreased electrostatic attraction, increased electron shielding

nonmetal reactivity trend down a period

• increase

• proton number increases, electrostatic attraction increases, attracting more electrons

Atomic radius

distance from nucleus to outermost shell

atomic radius trend down a group

• increase

• increased electron shielding, decrease electrostatic attraction, larger radius due to valence electrons not being held closely to nucleus

atomic radius trend across a period

• decrease

• increased protons: increased electrostatic attraction

Ionic radius

distance from nucleus to outermost electrons in an ion

Ionic radius: cations

Metals become ions when outermost shell is lost, there are more protons than electrons so electrostatic attraction increases

Ionic radius: anions

electron number increases, proton number stays the same. electrostatic attraction decreases. more electrons so more electron shielding

Ionic radius trend down a group

• Increase

• Shells increase, electron shielding increases, electrostatic attraction decreases

Ionic radius trend across a period

• decrease

• electrostatic attraction increases as there are more protons so ionic radius decreases

Collision Theory

• Reactant particles must collide

• there must be a certain minimum energy in the collision to rearrange bonds

• colliding particles must be correctly orientated in the collision

Kinetic theory

Degree to which particles move

Activation energy

Minimum amount of energy needed for particles to react

What does rate of reaction depend on

• Frequency of collisions between particles

• Energy which particles collide

Factors that speed up reaction rate

• concentration

• surface area

• pressure

• temperature

• catalyst

Concentration

At a higher concentration there are more particles in the same amount of space. this means that the particles are more likely to collide and therefore more likely to react

Surface area

Increased area for reactant particles to collide with, more collisions and a greater change of reaction

Temperature

When particles collide they do so with more energy and so the number of successful collisions increases

Speed

Reactions do not proceed at a steady rate. they decrease in speed over time because as the reaction progresses the concentration of reactants decreases

Calculating reaction rate from graphs

y/x or change in mass/change in time

Catalyst

Substance that speeds up a reaction, does not get used up and can be reused. lowers the energy required to start the reaction

Pressure

increased pressure: decreased volume and less space between particles so likelyhood of collisions increases

Single displacement

A single more reactive uncombined element displaces a less reactive one AB + C → AC + B

Double displacement

Parts of 2 aqueous ionic compounds switch places to form 2 new compounds AB+ CD → AD + CB

Synthesis

Two or more simple substances react to form one complex product A + B → AB