6.2 Electrons in the Atom
p. 127
Almost all of the properties of elements are
due to the electrons outside the nucleus.
Atoms interact with each other through their
electrons.
Chemical bonds involve only electrons, so
electrons determine how atoms combine.
Spectrum – the colors of light given off or
absorbed by an element.
Spectroscope – an instrument that separates
light into a spectrum (its different colors) (prism)
Spectral line – a bright colored line in a
spectroscope
The spectrum – Almost all the light and color
you see comes from atoms. Example: some
gases glow when electricity flows through
them – neon.
Each element has its own colors. All the colors
you see is from elements emitting or absorbing
light of only certain colors.
p. 128
Bohr Model of the Atom:
Light is a form of pure energy. The amount of
energy determines the color of the light. Red
light has low energy and blue light has higher
energy. Green and yellow have energy in
between red and blue.
Since atoms only emit certain colors of light,
that means something inside an atom can only
have a certain value of energy.
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Neils Bohr came up with the idea of energy
levels to explain the color spectrum of
hydrogen.
Energy levels are like steps on a staircase.
Electrons change energy levels by absorbing or
emitting light.
When an electron moves from a higher energy
level to a lower one, the atom gives up some
energy and emits it as different colors of light.
The specific colors correspond to the energy
between the energy levels.
p. 129 Electrons and Energy Levels
Electron cloud – electrons are so fast and light,
that their exact position cannot be defined.
The energy levels are at different distances
from the nucleus.
The positive nucleus attracts negative
electrons.
Higher energy levels are farther from the
nucleus and lower energy levels are closer to
the nucleus.
Rules for energy levels:
1. The energy of an electron must match one
of the energy levels in the atom.
2. Each energy level can hold only a certain
number of electrons.
3. As electrons are added to an atom, they
settle in the lowest unfilled energy level
Energy levels are predicted by quantum
mechanics, which is the science of physics that
deals with the microscopic world of atoms.
The energy levels on an atom are grouped into
different shaped called orbitals.
S-orbital is spherical and holds 2 electrons. The
first 2 electrons in each energy level are in the
s-orbital.
P-orbitals hold 6 electrons and are aligned
along the 3 directions on a 3-D graph (updown, back-front, right-left)