NATS 1745- Midterm Exam Guide - Comprehensive Notes for the exam ( 59 pages long!)
5 Oct 2017
School
Department
Course
Professor
York
NATS 1745
MIDTERM EXAM
STUDY GUIDE
History of Astronomy
NATS 1745 - Section A
Lecture 14 - Notes
July 1, 2017
PART 1: ATOMS
The spectra of stars and nebulae:
● How are bright/dark line spectra produced?
● In order to answer this, we need to understand atoms
**Remember:
- Dark line = absorption → eg stars
- Bright line = emission → eg nebulae
Brief history of understanding atoms:
● Democritus
a. 465 BCE
b. Ancient Greek
c. All matter is compiled of indivisible particles called atoms
d. Idea of cutting a piece of wood in half and then half and then half - enough times you
would get to the smallest particle (an atom)
● Dalton
a. 1803
b. (around the time that IR and UV was discovered)
c. ‘Billiard ball’ model (pool ball)
d. Matter is made of atoms, that are indivisible and indestructible
e. Atoms of elements are identical in mass and properties
f. Atoms can be neither created nor destroyed
g. Chemical reactions are an arrangement of atoms
h. Compounds are formed by two or more diff kinds of atoms
● JJ Thompson
a. 1904
b. Physicist
c. Did experiments to discover the electron → small negatively charged particles
d. ‘Plum pudding’ model of atom
e. Model looks like plum pudding (british desert), electrons are raisins in the pudding
f. Atoms were made up of material that was charged
g. Electrons (negatively charged) were embedded in positively charged matter
h. 1st important step in realising that atoms has 2 components, and that they have opposite
charges
find more resources at oneclass.com
find more resources at oneclass.com
i.
● Rutherford
a. 1911
b. Did experiments in UK and McGill
c. ‘Planetary’ model of atom
d. More accurate model
e. Positively charged nucleus
f. Orbited by negatively charged electrons
g. Most of atom is empty space
h.
i. Problematic:
j. Knew electrons were negatively charged and protons were positively charged, so why
wouldn’t the electrons be attracted to protons and spiral into the nucleus?
k. Wasn’t producing stable model of atom
l. We know atoms are stable because matter exists for long periods of time
● Bohr
a. 1913
b. One of the founders of quantum mechanics
c. Won nobel prize in 1922 for his model
d. Incorrect, but still useful
e. Based on improvements of Rutherford’s model
f. Predicts behaviour of dark/bright line spectra
g. Easy to visualise
h. Does produce reproducible results
i. Does produce what we see in nature
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
In order to answer this, we need to understand atoms. Dark line = absorption eg stars. Bright line = emission eg nebulae. Much like the solar system, each electron has a specific orbit, with one a little bit further out than the last. Ones furthest from nucleus have higher energies. **quantum mechanical model: (go back to lecture for more info) *p and n make up the nucleus. Each type of atom (or each element) has a specific number of p, n, and e- ^there is one uncommon type of hydrogen atom called deuterium (has 1 p, 1 n, 1 e-) ^less than 1% of all hydrogen as a neutron. Each type of atom is uniquely specified by its number of protons. Whole periodic table is built of diff types of atoms defined by its number of protons. In a neutral atom, the number of p and e- are equal.
