Chemistry Ch.2

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Chemistry
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Atoms & elements
updated 9 days ago by KC1999
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1

What is an atom?

  • The smallest identifiable unit of an element
2

How many naturally-occurring elements are there?

  • 91
3

How many synthetic elements have scientists created?

  • >20
4

What is the atomic theory in a nutshell?

  • The concept that all matter is composed of atoms
5

What are the 3 most important laws that led to the development & acceptance of the atomic theory?

  • The law of conservation of mass
  • The law of definite proportions
  • The law of multiple proportions
6

In 1789, Antoine Lavoisier formulated the law of conservation of mass. What does this state?

  • "In a chemical reaction, matter is neither created nor destroyed"
  • Basically.. the total mass of substances involved in the reaction does NOT change *much, I guess*
7

In 1797, French chemist Joseph Proust summarized his observations in the law of definite proportions. What does this state?

  • "All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements"
8

In 1804, John Dalton published his law of multiple proportions. What does this state?

  • "When 2 elements (call them A & B) form 2 different com- pounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers"
9

What is reductionism?

  • The idea that complex systems can be understood by understanding their parts.. including humans
10

When the concept of reductionism is applied to humans, what controversial questions are raised?

  • If atoms compose our brains, do those atoms determine our thoughts and emotions?
  • Are our feelings caused by atoms acting according to the laws of chemistry & physics?
  • Are our emotions nothing more than a series of atomic interactions with one another?
11

What is a cathode ray tube?

  • A partially evacuated glass tube constructed by English physicist J. J. Thomson in the late 1800's
12

What are cathode rays exactly?

  • Just a beam of e- emitted from the cathode of a high-vacuum tube
13

What did english physicist J. J. Thomson observe when working with his cathode ray tube?

  • That cathode rays traveled from (-) charged electrode (cathode) → (+) charged one (anode)
14

What did english physicist J. J. Thomson conclude about the particles that compose the cathode ray?

  • They travel in straight lines
  • They are independent of composition of material from which they originate (cathode)
  • They carry a (-) electrical charge.
15

What is electrostatic force?

  • An attractive & repulsive force between particles due to their electric charges
16

What is an electric field?

  • The area around a charged particle where electrostatic force exists
17

What is the charge of a single e-?

  • - 1.60 x 10-19 C
18

What's the mass of a proton in amu?

  • 1.007277 amu
19

What's the mass of a neutron in amu?

  • 1.008665 amu
20

Whats the mass of an e- in amu?

  • 0.00055 amu
21

What are the 3 types of radioactivity?

  • Alpha (α) particles (+ charged, most massive)
  • Beta (β) particles
  • Neutrons
  • Gamma (γ) rays
22

Whats the 1st basic part of the nuclear theory?

  • Most of an atom’s mass + ALL of its (+) charge is contained in the nucleus
23

What's the 2nd basic part of the nuclear theory?

  • Most of the volume in an atom is empty space, within that space is where e- exist dispersed
24

What's the 3rd basic part of the nuclear theory?

  • There are as many e- outside the nucleus as there are protons within the nucleus → making atoms electrically neutral.
25

If matter really is mostly empty space, according to Rutherford, then why in the hell can you slap your hand on a table & feel a solid thump?

  • Matter only appears solid due variation in its density → its on such a small scale that our eyes cannot see it → thus brains don't process it
  • I don't like that.. mm
26

All atoms are composed of the same subatomic particles, just in different proportions. What are those particles?

  • Protons
  • Neutrons
  • Electrons
27

In SI units, whats the mass of a single proton?

  • 1.67262 x 10-27 kg
28

In SI units, whats the mass of a single neutron?

  • 1.67493 x 10-27 kg
29

In SI units, whats the mass of a single e-?

  • 0.00091 x 10-27 kg
30

What is the assigned charge of a proton?

  • +1
31

What is the assigned charge of an e-?

  • -1
32

Which subatomic particles must be equal in magnitude to each other in order for the atom to be neutral or sum to a zero charge?

  • The protons & electrons
  • They are the only particles with charge
33

Why is matter normally charge-neutral?

  • B/c protons & e- are normally present in equal numbers
34

What's an example of matter dealing with a charge-imbalance?

  • Lightning! → build-up of (+) charge on ground & (-) charge in clouds → electrical discharge (lightning) occurs → equalizing/ correcting charge imbalance
35

What's the most important number to the identity of an atom?

  • The # of protons in its nucleus
  • This literally defines the element
36

What is the # of protons in an atom's nucleus called?

  • The atomic number
  • Represented as Z
37

Each element is identified by its own unique atomic number but also with a chemical symbol directly below it. How is it formatted?

  • As a 1 or 2-letter abbreviation
38

If the atomic number of an element is 2, the chemical symbol must be He. Why?

  • B/c He has 2 protons
39

All atoms of a given element have the same # of protons. However, they may not have the same # of what?

  • Neutrons
  • Ex: ALL Ne atoms contain 10 protons, but they may contain 10, 11, or 12 neutrons → each varying slightly in mass.. makes sense
40

What are atoms with the same # of protons, but different #'s of neutrons called?

  • Isotopes
41

What does the # of protons + the # of neutrons of an atom equal?

  • The mass number
42

How are isotopes symbolized?

card image
43

When do neutral atoms become ions?

  • When they gain or lose e-