Chemistry Unit 2

These cards are basic and effective notes to help you to remember the vital points for your Unit 2 Chemistry Exam. Have fun :P

I'd just like to thank Jackarias for providing me the info to help you lot.

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  • Consists of electrons surrounding a nucleus that contains protons and neutrons
  • Number of protons in an atom is called its atomic number
  • In the periodic table atoms are arranged in atomic number order
  • Electrons lie in energy levels or SHELLS(Not rings)

Particle -----> Mass (AMU) ---------> Charge ------------> Location

Proton --------------> 1 --------------------------> +1 -------------------> Nucleus

Neutron -----------> 1 ----------------------------> 0 ---------------------> Nucleus

Electron ----------> 1/2000 --------------------> -1---------------------> Orbiting Nucleus

  • The Mass Number (nucleons) of an atom is the TOP NUMBER
  • The Atomic Number (Number of Protons) is the BOTTOM NUMBER
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(Remember this isn't always necessarily correct.. the biggest number in that atom tends to be the Mass Number)

  • Elements consist of one type of atom only
  • Compound's are chemically bonded ( they are formed when two or more elements react together (chemically).)

It is important to note that it is difficult to separate the two original elements out again (unless it is a reversible reaction)

Isotopes are different atomic forms of the same elements, which have the SAME number of PROTONS ( but a DIFFERENT number of NEUTRONS)

Periodic Tables: Vertical columns = Groups. Horizontal rows = Periods

Group 1 elements - Alkali Metals; Group 7 = Halogens ; Group 0 = Noble Gases

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Chemical Bonding

  • Ions are electrically charged particles formed when atoms lose or gain electrons.
  • They have the same electronic structures as noble gases
  • Metal atoms form positive ions; Non- metals form negative ions.
  • The strong electrostatic forces of attraction between oppositely charged ions are called ionic bonds
  • Ionic Compounds have high melting points and boiling points
  • When an atom has a full outer shell it is stable and unreactive (like noble gases). However most atoms have no full outer shells
  • When atoms react, they take no part in changes which give them a stable arrangement of electrons. Done by:

SHARING ELECTRONS - i.e. Covalent bonding


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Ions are electrically charged particles formed when atoms lose or gain particles

There is a quick way to work out what charge on an ion should be:

  • The number of charges on an ion formed by a metal is equal to the group number of metal.
  • the number of charges on an ion formed by a non-metal is equal to the group number minus eight
  • Hydrogen form H+ ions

A covalent bond is a strong bond between two non-metal atoms

  • It consists of a shared pair of electrons
  • a covalent bond can be represented by a straight line or dot-and-cross diagram.
  • Hydrogen and chlorine can each form one covalent bond, oxygen two bonds, nitrogen three, while carbon can form four bonds.
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  • Range in size from about 100nm (nanometre) down to about 1nm
  • They are typically the size of small molecules, and far too small to see with a microscope.
  • Nanoparticles have a very large surface area compared to their volume. This makes them react faster and very quickly. They are very useful as catalysts.
  • i.e they can be used in self cleaning ovens and windows

Nanoparticles also have different properties to the same substance in normal sized pieces.

  • Used in sunblock creams to block harmful UV(UltraViolet) Light without appearing white on the skin.
  • Nano Science may lead to the development of: New Catalysts, New Coatings, New Computers, Stronger and lighter building materials, sensors that detect individual substances in tiny amounts
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Chemical Calculations

  • Ar = Relative Atomic Mass ( i.e. mass number)
  • Mr = Relative Formula Mass (i.e.the sum of Ar of a COMPOUND)
  • The Mr of a substance is known as the MOLE of that substance.
  • Percentage composition...

[(Ar x Number of atoms of that element) / (Mr of whole compund)] x 100

Empirical Formula =

  • 1. Write the mass given or percentage of element
  • 2. Mass / Ar
  • 3. Divide both numbers by smallest number
  • 4. The ratio becomes solution.
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Muhammad Suhayl


just to let you know... please rate and leave comments.. this set of cards is unfinished and i will add to this set very soon when my exams are over..




thank you brother, much appreciated.



You said:

Empirical Formula =

  • 1. Write the mass given or percentage of element
  • 2. Mass / Ar
  • 3. Divide both numbers by smallest number
  • 4. The ratio becomes solution.

I did this for a past paper:

Pb:                                                                          O:

6.21/207=                                                                0.64/16=

0.03                                                                         0.04

/0.03=    (DIVIDING BOTH BY SMALLEST NUMBER)          /0.03=

1                                                                              1.33 (2 d.p.)

 E-formula = PbO

This is what I wrote for a question in a past paper and I didn't get full marks. I was told to multiply 0.03 by 100 and told to multiply 0.04 by 100 to get 3 and 4. TH means the actual, correct answer was Pb3 O4  (3 atoms of lead and 4 atoms of oxygen).

So which method do I ALWAYS use?????????????????????????????

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