Unit 2 Chapter 1 Flashcards
(38 cards)
octet rule
tendency to prefer to have 8 electrons in the valence shell
empirical knowledge
obtained through results of experiments
theoretical knowledge
obtained through observations
*An attempt to use familiar ideas
to describe unfamiliar things in a
visual way.
*It can be changed as new
information is collected.
scientific model
Democritus VS Aristotle
Things are made of atoms VS 4 earth elements
Dalton’s Billiard Ball Model
THOUGHT atoms were indivisible (False)
Atoms of the same element have identical properties. ✅
- Atoms of different elements combine
in constant ratios to form compounds
(Law of Constant composition)✅ - Chemical reactions involve the
rearrangement of atoms; no new
atoms are created or destroyed (Law
of Conservation of Mass) ✅
Thomson
Empirical Evidence:
*As an electric current passed through a
gas, it gave off rays of negatively
charged particles.
* However, the gas was surprisingly
uncharged (neutral).
Conclusions:
*A particle smaller than an atom had to
exist.
– negative charges (e-s) came from
within the atom
ATOM WAS DIVISIBLE!
THOUGHT *There must be positively charged
particles in the atom, but he could never
find them.
Plum pudding
Thomson
FOUND ELECTRONS !!!
involved firing a stream
of tiny positively
charged alpha particles
at a thin sheet of gold
foil
* expected positive
charges to be spread
out evenly and
not enough to stop an
alpha particle
Rutherford’s Gold foil experiment
Empirical Evidence:
*Most of the positively charged alpha particles passed
straight through the gold foil.
*Some of the positively charged alpha particles
bounce away from the gold foil as if they
had hit something solid.
Rutherford’s Gold Foil Experiment Conclusion
Conclusions:
*Gold atoms in the sheet were mostly empty space.
– Atoms were not a pudding filled with a positively
charged material (Thompson).
*An atom has a small, dense, positively charged
center (i.e. NUCLEUS) that repelled the
positively charged alpha particles.
.: Nucleus is tiny compared to the atom as a whole.
HE FOUND PROTONS
_______ Model by rutherford
all of an atom’s positively charged
particles were
contained in the
nucleus.
* Negatively charged
particles were
scattered outside the
nucleus around the
atom’s edge.
Student of Rutherford - Chadwick
modified
Rutherford’s Mostly
Empty Space model
* atoms have a third
subatomic particle
being
NEUTRONS
in the nucleus
Bohr’s Planetary Atom Model
Electrons orbit the nucleus in circular
paths of fixed energy (ENERGY LEVELS).
* Electrons can jump (i.e.
transition) from energy level
to energy level.
* The higher the energy level, the
further it is away from the nucleus.
* PHOTONS are bundles of light
energy that that are emitted by
electrons as they go from higher
energy levels to lower energy levels.
ground state + excited state
Ground state is the lowest possible
energy level an
electron can be at.
excited state is an energy level
higher than the
ground state.
P.E.N
subatomic particles
Atoms of the same
element that have
a different #s of neutrons
yet they look, act
and react the
same.
isotopes
device to identify isotopes
mass spectrometer
Dobereiner
noticed a similarity
among the physical &
chemical properties
within several groups of
3 elements
- LAW OF TRIADS
– middle element had a
mass about halfway
between the atomic
masses of the other two
Newlands
arranged all known
elements in order of
increasing atomic
mass
- LAW OF OCTAVES
– repeating physical
and chemical
properties every 8
elements
Mendeleev
grouped elements with
similar properties in the
same column
– left blank spaces to add
elements
- PERIODIC LAW
– elements arranged by
increasing atomic mass
show a periodic
recurrence of properties
at regular intervals
Modern periodic law
When the internal
structure of atoms was
discovered,
Mendeleev’s Periodic
Law was revised
– elements arranged by
increasing atomic #
show a periodic
recurrence of properties
at regular intervals
sits atop group 1, but
it is not a member of
that family
* class of its own
* gas at room
temperature
* 1 p+ and 1 e-
in its
only energy level
* only 2 e-
to fill up its
valence shell
hydrogen
group 1
* 1 valence e-
* most reactive
metals
– with halogens and
oxygen
– violently with water
to make a base
* soft, silver, solids
@ SATP
alkali metals family
alkaline earth metals family
group 2
* 2 valence e-s
* react slowly with
water
* solid @ SATP
* react with air to form
oxides
* react with H+ to form
hydrides (except Be)
