PPT 2A Part 1 Flashcards
Who
- Matter could not be divided indefinitely
- Smallest piece of matter ; “atomos”
400 BC ~ Democritus
Who
Matter was made up of four “elements”
350 BC ~ Aristotle
- ATOMIC THEORY
1. All matter is made of atoms
2. Atoms of an element are identical
3. Each element has different atoms,
4. Atoms of different elements combine in constant
ratios to form compounds
5. Atoms are rearranged in reactions
1800 ~ John Dalton
Dalton’s theories
Mass can neither be created nor destroyed in any transformation of matter
Law of Conservation of Mass
Dalton’s theories
A pure compound is composed of the same elements combine in a definite proportion by weight
Law of Constant Composition
Who
Credited for the discovery of the proton
1886 ~ Eugene Goldstein
- Provided the first hint that an atom is made of even
smaller particles - Credited for the discovery of the electron
1897 ~ J.J. Thompson
Concluded that an atom has a small, dense,
positively charged center
1908 ~ Ernest Rutherford
Credited for the discovery of the neutron
1932 ~ James Chadwick
Atomic model and creator
Atoms are solid and indivisible
- Billiard ball model
- Dalton (1800 – 1900)
Atomic model and creator
Negative electrons in a positive framework
- Plum pudding model
- Thomson (1900)
Atomic model and creator
Atoms are mostly empty space, negative electrons orbit a positive nucleus
Rutherford’s model (around 1910)
Atomic model and creator
Electrons orbit the nucleus in “shells”, electron can be bumped up to a higher shell if hit by an electron or a photon of light
Bohr’s model / planetary model
Atomic model and creator
Electrons do not move in well-defined circular orbits
Quantum mechanical model (Erwin Schrödinger, Heisenberg, Born and many others)
Impossible to know simultaneously both the exact momentum of the electron and its exact location in space
Heisenberg’s Uncertainty Principle
Wave function which describes a specific distribution of electron density in space, has a characteristic energy and shape
Orbital
A → ___ = number of ___ + number of ___
- Mass number
- Protons; neutrons
Z → ___ = number of ___ in the nucleus
- Atomic number
- Protons
Charged particles due to loss or gain of electrons
Ions
Chemical reactions that release energy
Exergonic reactions
Chemical reactions that require or absorb energy from their surroundings
Endergonic reactions
Separated ions are ___ stable than atoms in an ___ bond
Less; ionic
Separated ions have ___ potential energy than atoms in a chemical bond
Higher
Energy is ___ to break a chemical bond
Required
Energy is ___ when chemical bonds form
Released
Russian scientist who published the basis for “Modern Periodic Table of Elements”
Dmitri Mendeleev
