Chemistry Lesson 1 - 3 Flashcards
What is Democritus theory?
- That atoms are small hard particles
- they are always moving
- come together to make different material
- in different sizes and shapes
What is Daltons theory?
- elements are made of small, indivisible particles (unique to each element)
- in chemical reactions: atoms sep, combine or rearrange in diff. ratios
What is Thomsons theory?
- Did experiment on cathoray - saw that electrons repel each other
- discovered electrons
- made plum puddling model - electrons are spread apart and being surrounded with the pudding which is positive
What is Rutherfords theory?
- gold foil experiment - found that the positive alpha particles are repelling the protons
- dissolved protons and nucleus
What is Bohrs theory?
- electrons can jump between orbitals by absorbing light photons
Model of atom:
Postulate 1 - electrons can move in a certain orbital, each corresponding to a specific energy level and where electron can move without LOSING ENERGY
Postulate 2 - electrons can only move from 1 orbit to another
What is Planck’s Quantum Hypothesis?
- light is made of photons (emit light) - no continuous and colour depend on stability of atom
What is the hydrogen spectrum?
- in a discharge tube, electrons become temp. excited and move further away from nucleus
Difference between long waves and short waves in length?
Long = low energy - does not move as far
Short = high energy - moves farther
What is the wave theory of light?
Light is a form of electromagnetic radiation
- in wave pattern
- travels at constant speed in vaccum
What did De Brogile propose?
Dual wave-particle properties of light may apply to matter
- electrons exist as “matter waves” around nucleus
What is the Wave-Mechanical model/who created it?
find the exact position and energy of electron in atom
- SCHRODINGER
What is the uncertainty principal/who created it?
- HEISENBERG
- it is impossible to know exact location and energy of electron
- rather the wave-mechanical model is a the probability of where the electron is
What is Aufbau’s principal?
Electrons must be added to lowest energy orbital first
What is Hund’s Rule?
Due to repulsion, all orbitals acquire 1 electron before getting the second
What is Pauli’s Exclusion Principal?
Electrons in same orbital have opposite spin + no 2 electron within an atom can all have same 4 quantum numbers
What are the exceptions of Aufbau’s Principal?
d4 and d9 - take from s so it becomes fill or half full (next best thing)
What is the exception of transition metals
- ions
- take from s for cations before d orbital
What are the implications of Schrodinger’s work?
- Orbitals - 3D cloud around nucleus
- Diff shape, size, distance from nucleus
- each orbital holds 2 electrons
- each energy level has 1+ cloud
—— ALL FROM QUANTUM #
What is isoelectronic?
Meaning having the same # of electrons
Trend in atomic radius
–> decrease, down = incrases
What is the trend in ionization energy?
IE1 < IE2 < IE3….
What is coordinate covalent bonds/Dative Bonds?
when 1 atom donates both of electron that share between 2 atoms - Dative bonds
- a covalent bond (a shared pair of electrons) in which both electrons come from the same atom TO CREATE ANOTHER BOND
What is resonance?
when there are multiple ways of writing a lewis structure