Chemical Bonds Involve Only Electrons, So Electrons Determine How Atoms Combine

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 (up-down, back-front, right-left)