Download Atomic structure 1 and 2 Lankani Wijesinghe

Preliminary Course: Atomic Structure
Lankani Wijesinghe
Outline
PART 1
• What is Matter?
• History of the atomic structure
• Atomic model
PART 2
• Introduction to the periodic table
• Properties of some main group elements
• Ions
Why learn atomic structure ?
Classification of matter
Classification of matter
Classification of matter
Different kinds of Atoms: The Elements
Atomic Theory of Matter
To Democritus, atoms were small,
hard particles that were all made of
the same material but were different
shapes and sizes.
To Democritus, atoms were small, hard particles that were all made of the same
material but were different shapes and sizes.
Atoms
were
infiniteininnumber,
number, always
Atoms
were
infinite
moving and capablealways
of joining
together.
moving
and capable of
joining together.
Atomic Theory of Matter
The billiard ball
Law of Multiple Proportions
The atomic theory makes sense!
Atomic Structure: Electrons
• J.J.Thompson (1897) applies
voltage to gas in a sealed tube
•Cathode rays are negatively
charged
•The charged particles which are
produced are found to have a
mass 1800 times smaller than
hydrogen
Plum pudding model
Thompson postulated that the negative particles reside within atoms,
balanced by a “delicious cake” of positive charge.
Beyond the Plum Pudding
Beyond the Plum Pudding
Rutherford's conclusions
Bohr’s Atom
Neils Bohr (1885–1962) refined Rutherford's
model in 1913 by proposing that electrons:
- orbit the nucleus without losing energy;
- could move only in fixed orbits of specific
energies.
- electrons with low energy would orbit closer to
the nucleus while electrons with high energy
orbit further from the nucleus.
Rutherford's –Bohr’s Atom
The neutron is discovered
The Atomic Model
The Nuclear Atom
Atomic Number
Mass Number
Isotopes
An example: Heavy water
Birth of the Periodic Table
Also took in to consideration
• density
• melting point
• reactivity
Mendeleev’s Periodic Table (1869)
Mendeleev’s Periodic Table (1871)
The Modern Periodic Table
The Modern Periodic Table
Metals, Non-Metals and Semi-Metals
Metals, Non-Metals and Semi-Metals
Metals
• conducts electricity
• has a metallic lustre
• malleable and ductile
Na
Au
Hg
C
Non-metals
• lack metallic lustre
• does not conduct electricity - good insulators
• brittle
Semi-metals (metalloids)
• It has some properties like a metal and
some properties are like a non-metal
Br
Si
Ge
Group 1: Alkali metals
• Soft, silvery metals
• Low melting points
• Very reactive with air and water
• Produces H2 when reacted with water
• Reactivity increases down the group
• One electron in the valence shell
Group 2: Alkaline earth metals
• Silvery metals
• Less reactive than alkali metals
• Produces H2 when reacted with water
• Reactivity increases down the group
• Two electrons in the valence shell
Group 17: Halogens
Cl
Br
• Chemically reactive
• Found in salts
• Used as disinfectants (eg. Cl, Br, I)
• Form acids when bonded to hydrogen (eg. HCl, HF)
• 7 electrons in the valence shell
I
Group 18: Noble gases
• Colourless, ordourless gases
• Highly unreactive
• Only heavier noble gases undergo some chemical
reaction
• Electronically stable
Electron discharge colour
Transition metals
Transition metals
Chemistry is all about electrons
Sodium wants to lose an electron!
(Na+)
Metals generally form CATIONS
Cu+, Cu2+ etc.
Chlorine wants an electron!
(Cl-)
Non-metals generally form ANIONS
Cations and Anions stick together
GOOD LUCK WITH YOUR FIRST YEAR
AT TRINITY COLLEGE DUBLIN !!