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1.5
1.
Atomic Size
Atomic Radius
This activity is about using atomic radii to define the sizes of atoms.
The radius of an atom is half the distance between the
nuclei of two atoms that are bonded together.
There are two types of atomic radius:
(1) The covalent radius is half the distance between the
nuclei of two atoms joined by a covalent bond.
On the diagram this is represented by half the distance
between E and F (r1).
(2) The van der Waals radius is the distance between the
nuclei of two atoms that are held together by van der
Waals forces.
On the diagram, this is represented by half the
distance between C and G (r2).
2.
Atomic Size And The periodic
Table
The purpose of this activity is to examine how atomic size changes
on going down a column in the periodic table and also on going
across a row.
Going Down a Group (column):
The size of an atom increases going down a group.
This is because on going down the group from one element
to the next, an electron energy level is added each time.
Going Across a Period (row):
The size of an atom decreases going across a period from
left to right.
This is because on going across the period from one
element to the next, a proton is added to the nucleus each
time.
This means that the positive nuclear charge is increasing.
The increasing positive nuclear charge pulls all of the
negative electrons closer to the nucleus making the atom
smaller.
3.
Atomic Size and Density
The purpose of this activity is to consider the densities of metallic
elements in relation to their atomic size.
The group 1 alkali metals have the lowest densities of the
metals.
This is because the electrons are held least tightly making
the atoms very big.
Group:
1
2
3
4
Going across the period the density of the atoms increases
since the mass is increasing but the size is decreasing.
Going down a group the density increases as the mass of
the atoms increases.