Atomic Structure
ATOM
• Smallest unit of matter
• An element is made up of the same
atom
▫ ex: Gold (element on P.T) is made
up of gold atoms
Parts of an Atom
• Atoms are made up of:
▫ Protons (p+): Positive charged
▫ Electrons (e-) : negatively charged
▫ Neutrons (no): no charge (neutral)
• These are called subatomic particles
• Nucleus is found in the centre of the atom
▫ The two subatomic particles found in the
PROTONS
nucleus are _________________
and
NEUTRONS
______________
• Shells (orbitals) are rings around the
nucleus
ELECTRONS
▫ ___________________
are located in the
shells outside the nucleus.
VALENCE SHELL
• VALENCE SHELL: outer most shell
▫ Electrons found in the valence shell are
called valence electrons
Determining number of protons,
electrons and neutrons...
# protons = ATOMIC NUMBER
# electrons = # protons (in a neutral atom)
# neutrons = ATOMIC MASS – ATOMIC NUMBER
EXAMPLE: Oxygen
atomic number = 6
Atomic mass= 16.00
# p=
6
# e=
6
# n=
16 – 6 = 10
Drawing Bohr-Rutherford Diagrams
1) Draw a circle representing the nucleus
2) Draw orbitals (dotted circles) around the
nucleus
▫
Hint: the period tells you how many orbitals
to draw
3) In the nucleus, indicate how many
protons (p+) and neutrons (n0)
4) Fill in the electrons on the orbitals
▫
▫
1st orbital: 2e2nd, 3rd, 4th, 5th, orbital – 8 e-
Let’s do an example!