Class notes
chem study guide part 2
- Course
- CHEM 223
- Institution
- Hunter College - Cuny
Lecture notes of 2 pages for the course CHEM 223 at Hunter College - Cuny (Guide for exam)
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Democritus: ancient Greek thinker believed that matter could be divided into smaller andsmaller particles until a basic particle was reached. He was the first to suggest the existence of
atoms
Atoms: the smallest particle of an element that retains both the chemical and physical properties
of that element
John Dalton: performed experiments to arrive at his Atomic Theory
John Dalton's Atomic theory:
1. All matter is composed of extremely small particles called atoms
2. Atoms of the same element are identical. Atoms of different elements are different
3. Atoms cannot be subdivided, created, or destroyed.
4. Atoms of different elements can combine in simple, whole-number ratios to form compounds
5. in chemical reactions, atoms are combined, separated or rearranged
Law of multiple proportions
Atoms of different elements can combine in simple, whole-number ratios to form compounds
1. Why isn't all of Dalton's theory true? Atoms can be broken down and atoms of the same
element are not identical because isotopes of that element exist
2. Atoms are made up of: protons, neutrons, and electrons
3. actual mass of protons and neutrons 1.67x10^-24 grams
4. Chemists use _______ comparisons of the masses of atoms relative
5. the unit of comparison is the atomic mass unit (amu)
6. Atomic mass unit: defined as 1/12 the mass of a carbon atom that contains six protons
and six neutrons
7. For all practical purposes the mass of a single proton or neutron is 1 amu
8. symbol of electron e-
9. relative electrical charge of electron 1-
10. Approximate relative mass (amu) of electron 1/1840
11. Actual mass of electron 9.11x10^-28
12. symbol of proton p+
13. Relative electricalcharge of proton 1+
14. Approximate relative mass of proton 1
15. actual mass of proton 1.67x10^-24 grams
16. symbol for neutron n^0
17. relative electrical charge for neutron 0
18. approximate relative mass for neutron 1
19. actual mass 1.67x10^-24 grams
20. John Dalton's model of the atom atom was invisible and the smallest particle that
could exist
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