Ch. 3.1-3.2 Flashcards
1
Q
chemist models
A
helps us understand the unseen
* can be visual, verbal, or mathematical
2
Q
for a model and theory to remain valid it…
A
MUST explain ALL known facts
MUST enable the scientists to make correct predictions
3
Q
Democritus
A
- 460-370 BC
- Proposed the existence of an atom; if a substance is cute into smaller piece eventually you will have the smallest possible piece
- Called the tiniest piece the atom
- Comes from “atomis “ meaning not to cut
4
Q
Aristotle
A
- 384-322 BC
- Rejected the idea of the atom
- Said matter could be cut continually
- Everyone believed him; idea of atom disappeared for 2,000 years
5
Q
Three laws of how chemical compounds are formed
A
- Later 1700s
- Law of Conservation of Mass
- Law of Definite Properties
- Law of Multiple Properties
5
Q
John Dalton
A
- Early 1800s
- Model of atom was introduced by him
- Developed first model in 1803
- Saw atoms as indivisible/indestructible
1) Believed all atoms of a given element were identical in: shape and mass.
2) Believed the atoms of different elements were different with a distinct shape, size, and mass
3) Believed that compounds were formed by combining two or more elements
6
Q
Johns Daltons theory prosper that atoms:
A
- Are the building blocks of life
- Are indivisible
- Of the same elements are identical
- Of different elements are different
- Unite in small, whole number ratios to form compounds
7
Q
J.J. Thomson
A
- late 1800s
- Credited with discovery of the electron
- Saw the atoms as a solid mass
- Made the first discovery of a subtonic particle from using catho-ray tubes
- Results found that the cathode-ray particles(electrons) are fundamental particles that are presents in tea toms of all elements
- Plum Pudding model: Negatively charged particles embedded in a ball of positive charge
8
Q
Lord Rutherford
A
- Early 1900s
- In 1901, indicated that atoms are largely made up of empty space
- Conducted the gold-foil experiment
9
Q
Gold-foil Experiment
A
- Aimed alpha particles at foil
- MOST passed through
- A FEW particles were deflected
- SOME particles bounced back
- Results: Most of the atom is empty space, an atom has a dense(positively charged) core surrounded by electrons
10
Q
Planetary Model
A
The model that Rutherford suggested that electrons orbit the positively charged nucleus, just like how planets orbit the sun
11
Q
model
A
a familiar idea used to explain unfamiliar facts observed in nature
12
Q
theory
A
an explanation of observable facts and phenomena
13
Q
Law of Conservation of Mass
A
- Matter is neither created or destroyed during ordinary chemical reactions or physical changes
- Happens because the atoms are all still there but separate to create the new product
14
Q
Law of Definite Proportions
A
- A chemical compound will have the same elements in the same proportions by mass regardless of sample size or where the sample came from
- No matter what sample of water you have, you will always have 11% hydrogen and 89% oxygen
