Unit 2: Structure and Properties of Matter Flashcards
Who discovered the atom?
The Greeks
Who invented the Modern Scientific Method
Robert Boyle
Who invented the Atomic Theory of Matter?
John Dalton
What are the 5 parts of the Atomic Theory of Matter?
1) All matter is made up of tiny particles
2) All atoms of a given element are identical
3) Atoms of different elements have the same properties
4) Atoms of different elements combine in constant ratios to form compounds
5) Chemical reactions involve the rearrangement of atoms. Atoms can’t be created or destroyed
What did JJ Thomson discover?
Atoms of many elements can be made to emit tiny negative particles
What is the Plum-Pudding Model (AKA Rasin Bun)
Negative electrons that are embedded into a positively chargers and spherical cloud
Who performed the gold foil experiment?
Ernest Rutherford
Who discovered the Neutron?
James Chadwick
What did Mac Planck start?
The quantum revolution but studying light emitted on hot objects
Quanta
A series of short burst of energy rather than a consistant steam
Quantum
One burst or packet of energy
Who discovered the photoelectric effect?
Heinrich Hertz
What is the formula for the photoelectric effect?
E=hf
- E: Energy in joules
- h: Planck’s constant (6.6 X 10^34 J/Hz)
- f: Frequency in hertz (Hz)
What are the 2 atomic states of hydrogen?
1) Excited State; Atom with excess energy
2) Ground State; Atom in lowest possible state
When an atom absorbs energy from an outside source what atomic state does it enter?
Excited
Whats the basis of boar’s theory of the hydrogen atom?
He used his observations of the line spectra to explain why electrons dont collapse into the atoms nucleus
Energy Level Diagram
- Energy in the photon that corresponds to the energy used by the atom to reach the excited state
- Each element produces it own unique colour spectrum which can be used to identify elements in compounds and mixtures
Quantized Energy Levels
Since only certain energy changes occur the H atom must contain discrete energy levels
Whats the 3 main points of Bohr’s model of the atom?
1) Quantized energy levels
2) Electron moves in a circular orbit
3) Electron jumps between orbits by absorbing or emitting photon of a particular wave length
Principal Quantum Number (n)
- Designated the main energy level of an electron
- Can be equal to 1,2,3,4,5,6,7
Secondary Quantum Number (l)
- Describes the shape of the electron orbit
- Equal to 0,1,2,3
Magnetic Quantum(ml)
- Describes the orientation of the electron orbit in space
- For each value of l ml can vary from -e to +l
- The number of values for ml is the number of independent orientations of orbits that are possible
Spin Quantum Number ms
- Describes whether an electron spins clockwise or counterclockwise
- ms can only be +1/2 or -1/2
What are the 4 pieces to finding a quantum number set?
1) Principal Quantum Number (n)
2) Secondary Quantum Number (l)
3) Magnetic Quantum(ml)
4) Spin Quantum Number ms
Energy Level Diagram
Shows the relative energies of electrons in various orbitals
What are the 6 rules for filling energy level diagrams?
1) Each circle is an orbital that can hold up to 2 electrons
2) Electrons are represented by arrows (# of arrows will equal atomic number of atom)
3) Arrows point up or down depending on their spin
4) s=1 circle (2 electrons)
5) p=3 circles (6 electrons)
6) d=5 circles (10 electrons)
Pauli Exclusion Principal
No 2 electrons in an atom can have the same 4 quantum numbers, meaning that the arrows in the orbitals must point in different directions
Aufbau Principle
Each electron is added to the lowest energy orbital available
Hund’s Rule
One electron occupies each of the orbitals at the same energy before a second electron can occupy the same orbital
Electron Configuration
- Provides the same information as the energy-level diagrams but in a more concise format
- Lists the number and kinds of electrons in order of increasing energy, written in a single line
What are the pros and cons of using Electron Configurations?
Pros- Efficient
Cons- Some energy may be lost
Shorthand Electron Configurations
Same as regular configurations but you start with the noble gas proceeding the element of interest
Example: Cl
[Ne] 3s^2 3p^5
What are the 4 rules for drawing lewis structures?
1) Use the last digit of the group on the periodic table to determine the number of valence electrons
2) Place one electron on each of the 4 sides of the nucleus before pairing
3) If there are more than 4 valence electrons pair them tas required
4) Use unpaired electrons to bond additional atoms with unpaired electrons to the central atom
What are the 6 steps to the procedure for drawing Lewis Structures? (Look in loose notes for examples)
1) Arrange atoms symmetrically around the central atom; usually listed first in the formula
2) Count the number of valence electrons of all atoms. For polyatomic ions, add electrons corresponding to the negative charge and subtract electrons corresponding to he positive charge on the ion
3) Place a bonding pair of electrons between the central atom and each surrounding atom
4) Complete the octets of the surrounding atoms using lone pairs of electrons (Hydrogen is an acception) Any remaining atoms go on the central atom
5) If the central atom doesn’t have an octet move lone pairs from the surrounding atoms to form double or tripe bonds until the central atom has a full octet
6) Draw the lewis structure and enclose polyatomic ions within square brackets showing the ion charge