Grade 11 Biology: Atoms and Molecules Review

A few points to remember:

1.  All matter is made up of small particles called ______________________which tend to combine together to form_______________________.

2.   All atoms of a type (e.g. all chlorine atoms) are________________________.

3.   Atoms have 3 basic sub-atomic particles. Fill in the following on

them:

Name of Particle Charge Location in the atom

      _____________           _______        __________________ 

      _____________           _______        __________________ 

      _____________           _______        __________________ 

Label the following diagram of an atom:

Stability

           Atoms are said to be unstable if their outermost electron shell is ____________ completely full. The first orbit is able to hold _____________ electrons while the second and third shells are each able to hold _____________ electrons. An atom will not will not react with others if its outermost shell is filled. Two examples of this are: ________________ and ____________________ which are called INERT. If an atom is unstable, then it must react by combining with other atoms to form _______________ compounds. Therefore, STABILITY is an indicator of the _________________ of an atom.

COMBINATIONS OF ATOMS

Atoms combine in two ways:

1.  ___________________ bonding involves a sharing of electrons so that the

outermost shell of each atom is filled.

Eg. Hydrogen    - has 1 electron in the outermost level.

      - needs 1 more electron to be stable.

      - will share with another hydrogen atom.

      - H₂ gas is formed.

2.  ____________________ bonding which involves a __________________ of

electrons. This creates an _______which is an atom with + or - charge.

Sodium (Na) - has _________ electron in its outermost level

    Chlorine (Cl) - has ________ electrons in the outermost level, and needs_____ more electron.

    The electron is transferred from ________________ to _________________so that the outermost level is _________________. The sodium ______________

an electron, so it now has a __________ charge and the chlorine ______________

and electron, so it has a ___________charge. Opposites attract and a molecule of salt is formed.