1. Chapter 2: Elements are the building blocks of matter

2. Chapter 2 – Elements are the building blocks of matter
A pure substance that cannot be broken down or separated into simpler substances
Made up of ONE kind of atom
More than 115 elements known

3. Chemical Symbols Internationally recognized
Consists of one or two letters
First letter is always capitalized
Second letter is always lowercase
Some symbols are related to the English names of the chemical (e.g. Helium is He), but some are related to the latin names (e.g. Gold is Au – for Aurum)

4. Elements can be: metals, non-metals or metalloids

5. Metals, Non-metals & Metalloids
Metals are:
Shiny
Malleable
Ductile
Usually solid
Good conductors of heat and electricity

6. Metals, Non-metals & Metalloids
Non-metals are:
Gases or brittle solids
Dull
Non-malleable
Non-ductile
Poor conductors of heat and electricity

7. Metals, Non-metals & Metalloids
Metalloids are:
Solids
Shiny or dull
Non-malleable and non-ductile
May conduct electricity
Poor conductors of heat
silicon
arsenic

8. Chapter 2.2 - The Periodic Table and Chemical Properties
Organizes the elements according to their physical and chemical properties
The one we use
was developed by
Dmitri Mendeleev
in 1867

9. Mendeleev’s Periodic Table
Mendeleev’s two main contributions:
He organized all the known elements according
to properties and characteristics
He recognized
the need to
leave spaces
for elements
not yet
discovered

10. The Periodic Table Includes each element’s Name - Symbol
Atomic number - Atomic mass

11. Some things to remember:
Atomic Number = # of protons
# protons = # electrons (neutral charge!)
Atomic numbers increase one by one
A carbon atom has 6 protons and 6 electrons!

12. Some things to remember:
Atomic mass is the average mass of the atoms of an element (measured in amu)
When you round the atomic mass, you get the mass number (which equals the number of protons and neutrons in an atom of an element)
The atomic mass is amu, so the mass number rounds to 12...
So there are 12 protons and neutrons in total

13. Some things to remember:
So the # of neutrons can be calculated by:
mass number – # of protons (atomic #) = # neutrons
The atomic mass /mass number tend to increase with the atomic number , but there are exceptions
In a carbon atom, the
number of neutrons:
mass # - # protons = # neutrons
12 – 6 = 6 neutrons