Chemical similarities of elements are based on their
of valence electrons
FACT
All elements in the same group have the same number of valence electrons and therefore have similar chemical properties
Periods are which direction
- Horizontal
- Period corresponds to the outermost PEL being filled with valence electrons
Groups are which direction
- Vertical
- All elements have the same number of valence electrons
Atomic Radius
- The distance between the nucleus and the outermost valence electron in an atom
- Found on Table S
Trends in Atomic Radius
Down a group: Atomic radius increases (more orbitals)
Going Across a Period: Atomic radius decreases (due to increased nuclear pull → Because of more protons being added!)
Ionic Radius
When atoms gain electrons IONIC RADIUS INCREASES
When atoms lose electrons IONIC RADIUS DECREASES
Ionization Energy
The energy required to remove the most loosely held valence electron
Trends in Ionization Energy
Going down a group: IE DECREASES
Going Across a Period: IE Increases
Electronegativity
The ability of an atom to attract electrons to itself to form a bond
Trends in Electronegativity
As you go down a group, electronegativity DECREASES
Going across a period, Electronegativity INCREASES
Allotrope
Non-metal that can exist in two or more forms in the same phase, that have different structure and properties!
Allotrope Examples:
Oxygen & Ozone (both made of oxygen)
Diamond & Graphite (Both made of Carbon)
Properties of Metals
- Solids (except for Hg liquid)
- Shiny
- Malleable
- Conductors of Electricity
- Low Ionization Energy
- Low EN
- Large Atomic Radius
- Tendency to form positive ions
- High MP/BP
Metalloids
- Properties of metals and nonmetals
- Average EN, IE, and atomic radius
- Highish MP/BP
- Solids
Non Metals
- Solids, Liquids (Br), and Gases
- Poor conductors of heat and electricity
- Dull
- Form Negative Ions
- High EN and IE
- Smaller atomic radius
- Low MP/BP
Highest EN Value:
Lowest EN Value:
- 0 (Fluorine)
0. 7 (Francium)
Alkali Metals
- Group 1
- All have 1 valence electron
- Only found in compounds or salts b/c so reactive
Alkaline Earth Metals
Groups 2
-All have 2 valence electrons
Transition Metals
- Groups 3-12
- Form COLORED ions
- Less reactive than groups 1 + 2
What happens to metallic properties and reactivity as you go right on the periodic table?
They decrease
Noble Gases
- Group 18
- Full octet of valence electrons therefore non-reactive and stable
- Very high IE
Halogens
- Group 17
- All non-metals
- High EN and IE
- Diatomic elements (never alone)
- Highly reactive
