1.5 Atomic Size

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1.5 Atomic Size

• Atomic Radius

LO I know what an atomic radius is.
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There are two types of atomic radius.

• The radius of an atom is half the distance
  between the nuclei of two atoms that are bonded
  together.

covalent
(1) The radius (r1) is half the
distance between the nuclei of two atoms joined
by a covalent bond (E-F).
van der Waals
(2) The radius (r2) is half the
distance between the nuclei of two atoms joined
by van der Waals forces (C-G).
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• Atomic Size and the Periodic Table

LO I understand trends in atomic radii
throughout the Periodic Table.
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So, the size of the atoms increases.

• Going down a group

• The number of electron energy levels increases.

Going across a period

• The number of protons in the nucleus increases.

• The increasing nuclear charge pulls all of the
  electrons closer to the nucleus.

The size of the atoms decreases going across a
period from left to right.
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• Atomic Size and Density

LO I understand how density changes with atomic
size.
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So, the density of the atoms increases.

• Going down a group

The mass of the atoms increases more than the
size does.
Going across a period
The mass of the atoms increases as the size
decreases.
So, the density of the atoms increases.