Unit 1- Chemical Bonding Flashcards
1
Q
Explain Bohr’s Structure of an Atom
A
- Niels Bohr (1913) agreed with Rutherford’s model of a nucleus surrounded by a large volume of space
- It did something Rutherford’d did not- Focus On The Electrons
- Neutrons and protons occupy the nucleus
- Electrons move with constant speed in fixed orbits around the nucleus, much like planets orbiting the sun
2
Q
Explain the Bohr Model in terms of energy
A
- Each electron has a specific amount of energy
- If an atom gains or loses energy, the energy of the electrons can change.
- The possible energies that electrons can have are called energy levels
- Energy levels can be thought of as steps on a staircase
- Whether you are going up or down you can only move in whole step increments
- Electrons cannot exist between energy levels just like you can’t stand between steps
- The lowest step is the lowest energy level called the ground state. Each step above this represents a higher energy level.
- If an atom gains or loses energy, electrons can respectively move up or down energy levels
3
Q
Explain a Continuous Spectrum vs A Line Spectrum
A
- Objects at a high temperature emit a continuous spectrum when viewed through a diffraction grating. Continuous spectrums contain all the wavelengths in a given range.
- When a sample of an individual element is heated and the emitted light passed through a diffraction grating, only a few lines, called a line spectrum are observed (Ex. H2) A line spectrum contains only a few wavelengths
4
Q
How do scientists measure energy changes?
A
Scientists measure energy changes in an atom by the type of visible light that is given off by the object, what is referred to as the emission spectrum
5
Q
Explain how H2 could produce a line spectrum
A
- the electricity causes H atoms to gain energy, exciting them to move to higher energy levels
- H atoms then release this energy and return to ground state by emitting certain wavelengths of visible light
- These wavelengths correspond to distinct colours and indicate the amount of energy gained and lost
6
Q
Explain what was right and wrong about Bohr’s model of the atom
A
- Bohr’s model was improved as scientists made further discoveries
- Bohr was right in assigning energy levels to electrons
- He was wrong in assuming electrons moved like planets orbiting the sun as in reality electrons are much more unpredictable
7
Q
What did Louis de Brogile propose?
A
- Louis de brogile (1924) proposed that electrons, previously thought of as particles, have properties of waves- what we now call “wave particle Duality”
- He went further to derive an equation that describes the wavelength of a moving particle
8
Q
What were Erwin Schrodinger’s thoughts on the electron?
A
- In 1926, Erwin Schrodinger adds that electrons behave like circular standing waves around the nucleus
- Standing waves consist of wavelengths that are multiples of WHOLE NUMBERS, any other orbits not being allowed because they would cause the wave to collapse
- This agrees with the idea that only certain electron energies exist
- He then created a wave function (equation) to calculate energy levels
9
Q
What were Werner Heisenberg’s thoughts on the electron?
A
- In 1926, Werner Heisenberg took a statistical approach to locating an electron
- His uncertainty principle states that it is impossible to know the exact position and speed of an electron at a given time
- The best we can do is describe the probability of finding an electron in a specific location
10
Q
Explain the electron cloud model
A
- The works of de brogile, schrondinger, and heisenberg lead scientists to understand that they must deal with probability when trying to predict the locations and motions of electrons in atoms
- An electron cloud is a visual model of the most likely locations of electrons in an atom
- The electron cloud represents all the orbitals in an atom
- An orbital is a region of space around the nucleus where an electron may be
- 3-D space that defines where electron may be not 2-D track
- The electron cloud model is a good approximation of how electrons behave in their orbitals
11
Q
Explain the Quantum Mechanical Model
A
Our current Understanding:
- Electrons move around the nucleus in orbitals, as represented by a 3-D electron cloud
- The electron cloud is based off of wave functions and probability
- Orbitals can overlap
- Electrons can move to different orbitals by absorbing/ emitting energy
12
Q
What is electron configuration and what does it determine?
A
- Electron configuration is how electrons are arranged in orbitals around the nucleus
- It is important because it determines the chemical behaviour of every element
- Certain rules govern how electrons fill up orbitals and at what energy levels and sublevels these orbitals are found
13
Q
What are energy levels and how many are there?
A
- Energy levels are areas at specific distances from the nucleus (same as Bohr’s energy levels) where electrons are found
- There are 7 known energy levels which correspond to the period (row) numbers (i.e rows). Energy levels are symbolized with the letter n (e.g n=1)
14
Q
Explain what happens as energy levels get higher.
A
- The higher the energy level, the greater the distance from the nucleus
- These electrons are not attracted as strongly to the nucleus and thus are more readily available for bonding
15
Q
Explain Sublevels and Their Shapes
A
- Each energy level contains sublevels, each with their own distinct shape and amount of energy. There are four sublevels.
- S orbital: spherical
- p orbital: dumbbell
- d orbital: cloverleaf
- f orbital: flower
- Each sublevel has a set number of orbitals, locations in which the electrons are most likely to be found
- The number of sublevels available depends on the energy level
16
Q
Why are the energy levels not as expected?
A
- Electrons fill orbitals in a way to minimize the energy of the atom. Therefore, the electrons fill the principal energy levels in order of increasing energy (the electrons are getting farther from the nucleus)
