Chem - Lecture 01b

Question 1

What are elements

Answer 1

substances that cannot be separated into simpler substances

Question 2

There are ___ known elements, with a variety of abundances

Answer 2

There are 118 known elements, with a variety of abundances

Question 3

what are compounds

Answer 3

Substances that aren’t elements but are instead composed of 2 or more elements combined chemically in defined proportions

• e.g. H2O, NaCl

Question 4

Physical change

Answer 4

a change that alters only the state or appearance of a substance

i.e. the change doesn’t alter composition

• e.g. dry ice (solid CO2) going directly from a solid to a gas – a process known as sublimation

Question 5

Chemical change

Answer 5

a change that alters composition

chemical changes transform one or more pure substances into one or more new pure substances

• e.g. Iron and oxygen react to form rust (iron oxide)

Question 6

And now for the foundational concept of chemistry

Answer 6

THE ATOM!

Question 7

Atomic Theory of Matter
• Hypothesizing structure to explain properties/results (early 1800s)
– Law of definite proportions
– Law of multiple proportions

Answer 7

Atomic Theory of Matter
• Hypothesizing structure to explain properties/results (early 1800s)
– Law of definite proportions
– Law of multiple proportions

Question 8

Structure of the Atom

• Experiments of the late 19th century showed that atoms themselves had an ______ structure

Answer 8

Structure of the Atom

• Experiments of the late 19th century showed that atoms themselves had an internal structure

Question 9

Electron
• JJ Thompson – electron’s ______-__-______-______
• Milliken – electron’s charge

Answer 9

Electron
• JJ Thompson – electron’s mass-to-charge-ratio
• Milliken – electron’s charge

Question 10

Structure of the Atom
• So what does an atom look like?
– So we know the ______ is tiny and dense, but leaves the all-important question:
• How are ______distributed around the ______?

Answer 10

Structure of the Atom
• So what does an atom look like?
– So we know the nucleus is tiny and dense, but leaves the all-important question:
• How are electrons distributed around the nucleus?

Question 11

Structure of the Atom
• The tiny/dense ______ (positive) that’s surrounded by a “cloud” of ______(negative) – You’ll often hear me call this the “______ density” and the “charge ______”

Answer 11

Structure of the Atom
• The tiny/dense nucleus (positive) that’s surrounded by a “cloud” of electrons (negative) – You’ll often hear me call this the “electron density” and the “charge density”