Periodic table part II

The Periodic Table of Elements

Who created the modern periodic table?
What does the periodic table tell us?

Dmitri Mendeleev:
- Wrote down the names of the known elements on its own card along with the known properties such as densities, melting point, boiling point
- Sorted and re-sorted the cards into rows and columns until he found a pattern
- Left gaps in the rows and columns to predict the properties of the elements that were later discovered.

What the table tells us
- Atomic number – number of protons in the nucleus of each atom of an element. Increases from left to right and from top to bottom on the table.
- Atomic mass – found by adding the number of protons and neutrons in the nucleus.
- Ion charge – electric charge that forms on an atom when it gains or loses an electron. When an ion loses electrons (the case in the metals) it has a positive charge, whereas when an atom gains an electron (the case in non-metals) it has a negative charge. Some elements (such as transition metals) have multiple charges and can form ions in more than one way.

Periods and Families

Alkali Metals
- Highly reactive
- Reactivity increases as you travel down the 1st column

Alkaline Earth Metals
- Less reactive than the alkali metals
- Will burn in air if heated
- Used in Fireworks
- Found in the second column

Halogen Gases
- Non metal and highly reactive
- Flourine is the most reactive and Iodine is the least

Noble Gases
- Most stable and unreactive elements in the periodic table
- Some (argon and neon) are used in light fixtures and glow in distinctive colours.

Properties of metals and non metals