The Importance of Electrons In the behavior of Atoms

Important Behaviors of Electrons 1. An atom is able to maintain its spherical shape because the electrons move around in the outermost space that surrounds the nucleus. 2. The atoms of an element is electrically neutral and stable because it has the same amount of negatively electrons as positively charged protons

Important Behaviors of Electrons 3. In a chemical reaction electrons are responsible for forming CHEMICAL BONDS. 4. When electrons are transferred between atoms they form ionic compounds ex;- Sodium Chloride – table salt. 5. When electrons are shared between the atoms they form covalent molecules ex:- Oxygen Molecule O=O or O2 .

Behaviors of Electrons 6. The process of removing electrons from an atom by friction does not alter the chemical identity of the atom on the physical properties. 7. Electrons are responsible for the various shapes of compounds and molecules ex – the bent shape of the water H2 O molecule and the pyramidal shape of Methane Gas - CH4

Behavior Electrons 8. According to both the Bohr Model and the Quantum Model of the atom the electrons have a fixed amount of energy referred to as a QUANTUM of ENERGY. 9. When the electrons are in the lowest energy level close to the nucleus they are in the GROUND STATE.

Behaviors of Electrons 10. When they absorb outside energy they are in an EXCITED STATE and move to a higher energy level. 11. After a short period of time the excited electrons will release their extra energy and return to the ground state. 12. The released energy is seen as different colors of light on the Line Emission Spectra. 13 Red light has a lower energy content than Blue light.

Behaviors of Electrons 14. Spectrum analysis reveals that each element on the periodic table exhibits a unique line emission spectrum that clearly confirms the identity of element.

Behavior of Electrons 15. The flow of electrons is called ELECTRICITY. 16. Electricity caused MAGNETISM. 17. Together we say electrons have ELECTROMAGNETIC ENERGY 18 Electrons exhibit wave-like properties when they emit photons of light in different colors.

Two Natures of Electrons DUALITY 1. Sometimes electrons behave like particles of matter because they have a mass; a charge; building block of all matter; partake in chemical reactions etc 2. Sometimes electrons behave like waves because they release energy in the form of colors of light waves that are in the VISIBLE SPECTRUM.

ELECTROMAGNETIC THEORY Because of these two characteristics – dual nature, scientists developed the ELECTROMAGNETIC THEORY as current theory for explaining the behaviors of atoms and electrons.

Bohr Atomic Model (1913) Proposed the Hydrogen Atomic Model The model indicates that a. the electron circulate the nucleus in allowed ORBITS b. each ORBIT has a fixed or definite energy requirement. c. the ORBIT CLOSEST to the nucleus requires the LOWEST amount of energy. The ORBIT FURTHEREST away requires the HIIGHEST amount of energy. The electrons cannot occupy a space between the orbits in the same way that you could not stand between the steps on a ladder

Bohr Atomic Model The electron is in GROUND STATE in the orbit CLOSEST to the NUCLEUS. The electron must absorb a PHOTON (packet of energy) to move to the higher orbit – the process is called ABSORPTION and the electron is in the EXCITED STATE. When the electron falls back to the ground state it emits a photon of light - the process is called EMISSION. Spectral Analysis of the emitted light using a spectroscope equipped with a prism separates the component colors – LINE EMISSION SPECTRA

Quantum Model Electrons behave as waves when they produce different colors of light. Electrons are detected by their interactions with light photons. In the experiment - PHOTOELECTRIC EFFECT - light shone on metals released electrons. In Plank’s Hot Body Experiment –in a heating process metals exhibit various colors similar to the colors that make up the VISIBLE SPECTRUM.

Quantum Model EINSTEIN’S analysis of both experiment indicate that electrons have two basic nature: A. Particle like properties (mass & charge) B: wave-like properties ( released light energy) EINSTEIN also indicated that a LIGHT PHOTON also has TWO BASIC properties: A. Particle like ( Packet of energy) B. wave-like ( frequency, wavelength, energy)

Quantum Model Electrons move around the nucleus in orbital that are situated a cloud The orbitals are three dimensional. Quantum Energy is the minimum energy that can be lost or gained by an atom. There are 4 Quantum Numbers needed specify the atomic orbitals and properties of the electrons in each orbital.

4 Principal Quantum Numbers 1. The Principal Quantum Number 2. The Angular Momentum Quantum Number 3. The Magnetic Quantum Number 4. The Spin Quantum Number

The Principal Quantum Number Indicates the main energy levels occupied by the electrons. Symbolized by letter “n” It is the same as Energy Level or Shell The lowest energy level is closest to the nucleus and n = 1

Angular Momentum Quantum Number Indicates the shape of the orbitals s–shape only 1 sub-level – 2 total electrons p-shape – 3 sub-levels – 6 total electrons d-shape – 5 sub-levels -10 total electrons f-shape – 7 sub-levels – 14 total electrons

Magnetic Quantum Number Indicates the orientation around the nucleus. For example the S – shape orbital has a spherical orientation P-shape has 3 different orientations px ; py ;pz D-shape has 5 different orientations F-shape has 7 different orientations

The Spin Quantum Number The spin gives electrons their magnetic effect. Each orbital and/or sublevel can hold only two electrons. The two electrons exist in one of two possible spins – A: clockwise B: counterclockwise

Properties of Electromagnetic (ER) Waves 1. All ER waves travel at the same speed as visible light 3.0 x 108 m/s. 2. Each has a specific frequency - the number of waves that pass a given point in 1 second. 3. Each has a specific wavelength – the distance of one complete trough and crest. 4. They have minimum potential energy in the ground state

Wave Equation and Units Wave speed = Frequency x Wavelength V = f x Wavelength V - Speed units = meter/second (m/s f- frequency = 1/second or Hertz (Hz) Wavelength = meters, nanometers (nm = 10-9 m) The metric prefix nano means 10 -9

Wave Energy or Quantum of Energy Quantum Energy is the minimum energy that can be lost or gained by an atom. The minimum energy correspond to the minimum frequency. If the electron does not absorb the minimum energy then it will remain at that position. The energy Unit is JOULE .

Quantum of Energy Equation Plank’s Equation E = Plank’s Constant x Frequency E = h x f PLANK’S CONSTANT = 6.626 x 10 -34 J.s

What are some applications of the Electromagnetism? 1. Role in speakers 2. microphones 3. car starters 4. doorbells 5. MRI magnetic Resonance Imaging 6. Radio and Television operations 7. AC generator delivery of electricity 8. Electromagnetism is responsible for the electrical signals in heart, brain, nerve, 9. Electromagnetic waves from the sun makes life possible through photosynthesis.

The wave frequency is inverse to the wavelength. Explain the Relationship between wave Frequency, Wavelength, Speed and Energy The wave frequency is inverse to the wavelength. When the frequency is low (slow waves) the wavelength is long. When the frequency of the wave is high(fast waves) the wavelength is short. The energy of the wave is directly proportional to the frequency.