2.1: History of Elements and Compounds

Question 1

What are some of the basic concepts of chemistry

Answer 1

• Elements are the basic unit of matter
• Atoms are the smallest units of an element
• Atoms make up everything in our universe (except some energy and other particles)
• 25 elements are essential for life

Question 2

What does the periodic table show for each element

Answer 2

• the atomic number is the number of protons
• the atomic mass is the average of the number of neutrons + protons, protons remain constant but neutrons can vary between variations called isotopes

Question 3

What are noble gases

Answer 3

Elements that do not react with others and form bonds
Electrons are added in layers, and a noble gas has all the possible electrons in the other (valence) layer, so they are happy

Question 4

What did ancient philosophers think of elements

Answer 4

Thales (640-546 BCE) though water was the base of all matter
Anaximenes (570 BCE) though air
Heraclitus (540-475 BCE) though fire
Empedocles (490-430 BCE) though water, earth, air and fire combined to form all matter.
Aristotle (384-322 BCE) though a 5th ether made heavenly bodies

Question 5

What is the history of elements and compounds

Answer 5

Between 300 BCE - 1600 CE, 14 primary substances like silver and sulphur were added to the old elements
Robert Boyle (1627-1691) began classifying matter into elements, matter that could not be broken down further, and compounds which were joint matter
This classification lead to discovery of more elements, the invention of chemical symbols by Jons Jakob berzeling in 1814 and the discard of Aristotle‘s elements

Question 6

What are the three fundamental laws of chemistry?

Answer 6

1. the law of conservation of mass
2. the Law of defined proportions
3. the law of multiple proportions

Question 7

Explain the first fundamental law of chemistry

Answer 7

In a chemical reaction, the total mass of all reactants will equal the total mass of all products

Question 8

Explain the second fundamental law of chemistry

Answer 8

A specific compound always contains the same elements in definite proportions.
Water is always H20 not H3O
also a compound always contains the same proportions of elements by mass In water Oxygen is 8/9 of the mass
This is also called the law of constant composition.

Question 9

Explain the third fundamental law of chemistry

Answer 9

Some combination of elements may be capable of forming more than one compound
for example, carbon and oxygen can make CO or CO2