Studied by 2 people
What is an element?
A substance made up of only one type of atom which cannot be split into anything simple
What is a compound?
Pure substance made up of 2 or more elements chemically combined
What is a mixture?
A combination of 2 or more substances physically, not chemically
Can be separated physically(filtration, evaporation)
Describe the structure of an atom
Central nucleus containing neutrons and protons surrounded by shells of electrons
What is the relative charge and relative mass of a proton?
Relative charge= +1
Relative mass= 1
What is the relative charge and relative mass of a neutron?
Charge= 0
Mass= 1
What is the relative charge and relative mass of an electron?
Charge= -1
Mass= 1/2000
What is the atomic number?
Amount of protons in the nucleus of an atom
Smallest number on periodic table
What is nucleon number?
Total amount of protons and neutrons in the nucleus of an atom
How to determine how many shells an element has in electronic configuration?
Period number/row number
How to determine how many outer shell electrons an element has?
Group number of element
Eg: O is in grp 6, therefore has 6 outer electrons
What is a noble gas?
An element which has 8 outer electrons
All grp 8 elements r noble gases
What is an isotope?
Different atoms of the same element which has:
Same proton number
Different amount of neutrons
Same number of electrons
Why do isotopes of the same element have same chemical properties?
Because they have same number of electrons, therefore same electronic configuration
How to calculate relative atomic mass in %
Ar=[(%of isotope A x mass of isotope A)+(%of isotope B x mass of isotope B)]/100
How are cations formed?
Positive ions are formed when they lose electrons, so they have more protons than electrons
How are anions formed?
Negative ions are formed when they gain electrons, so they have more electrons than protons
What is ionic bonding?
A strong electrostatic attraction between oppositely charged ions
Describe dot and cross diagram
Only outer electrons are shown
Charge of ion is spread evenly, shown by using square brackets
Charge of each ion is written on top right corner
Describe the giant lattice structure of ionic compounds
(State which ions are present)
Regular arrangement of alternating positive and negative ions connected by strong electrostatic forces
What are the properties of ionic compounds
High melting point and boiling point
Good electrical conductivity when aqueous or molten
Poor electrical conductivity when solid
Why do ionic compounds have high melting and boiling points?
The strong electrostatic forces known as ionic bonds require a lot of energy to break
Which is why ionic compounds have high mp and bp
Why do ionic compounds have poor conductivity when solid and high conductivity when liquid?
When solid, ions r fixed and cannot move, so they r poor conductors
When liquid, the ions can move and carry charge, therefore have high conductivity
Remember
When explaining properties, always state:
Type of structure(lattice)
Type of bonds/forces(ionic bonds/electrostatic forces)
What is the relation between charges and strength of ionic bonds in ionic compounds?
Smaller charge=weaker ionic bond, therefore less energy required for bond breaking, lower mp
Bigger charge=stronger ionic bonds, therefore more energy required for bond breaking, higher mp
Note
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