Periodic Table-Chemistry Regents

Purpose of the Periodic Table

1. Organize all known elements

2. Brought to order what was thought to be unrelated facts

3. Help predict the existence of undiscovered elements

Mendeleev

1. Arranged elements according to mass

2. Arranged elements with similar chemical properties in columns

3. Considered the Father of the Periodic Table

Mosley

Arranged the periodic table by atomic number

Periodic Law

Chemical proprieties are functions of atomic numbers, so today's Table is arranged by atomic number

Periods

1. Horizontal rows

2. Period number indicates number of the Principal Energy Level

Groups or Families

1. Vertical columns

2. Each element in group 1, 2, and 13 have the same chemical properties because they have the same number of valance electrons

Metals

Found on the left of the staircase except H

1. Solids except for Hg (liquid)

2. Malleable (hammered into sheets)

3. Ductile (pulled into wire)

4. Luster

5. Low ionization energy and electronegativity

6. Good conductors of heat and electricity

Nonmetals

Found right of the bold staircase

1. Exist in all phases of matter (only liquid is bromine)

2. Not malleable, ductile, or shiny

3. Solids are brittle

4. High electronegativity and ionization energy

5. Poor conductors of heat and electricity

Metalloids/semimetals

B, Si, Ge, As, Sb, Te, At

1. All solids

2. Display properties of metals and nonmetals

Atomic Radii trend

1. Increase as you go down a group because there are more electron shells

2. Decrease as you go across a period because nuclear charge increases and pulls the electrons closer

Ionic Radius

Size of the ion formed when an atom loses or gains electrons

Ionic Radius METALS

They lose electrons and become smaller (lose a principal energy level)

-parent atom is larger than the ion

Ionic Radius NONMETALS

Gain electrons and become larger

-The added electrons cause the protons to loosen their hold over the electrons and the radius expands

NUMBER OF PRINCIPAL ENERGY LEVELS DO NOT CHANGE

Ionization Energy

Energy required to remove the outermost loosely held electron from an atom

Ionization Energy Rules

-Increases across the table

-Decreases down the table

As you go down the atoms are larger and the valence electrons are held less tightly to the atom

Up and to the right = high ionization energy

Electronegativity

An atoms ability to attract electrons

-Highest value is Flourine (4.0)

-Increases across the table

(Nonmetals want to fill valence energy level)

-Decreases down the table

The nucleus of a larger atom can not pull the electrons from other atoms very easily (less force of attraction)

Up & to the right = HIGH electronegativity

Metallic Character

The easier an atom loses electrons, the more metallic character it has (& MORE REACTIVE)

*Fr most reactive metal & most metallic

across the table

Group 1

ALKALI METALS

-Metals

-Very reactive (most reactive metals)

- Only exist in compounds

-Reactivity increases as you go down the family cause ionization energy

-Francium is the most reactive metal

-Soft

-Low density

-Low melting points

-low ionization energy

Group 2

ALKALINE EARTH METALS

-Metals

-Not quite as reactive as group 1

-Only exist in compounds

-Low densities, not as low as group 1

-Higher melting points than alkali metals

Groups 3-12

TRANSITION METALS

- Ions are usually colored as solids and in aqueous solutions

- Cu is blue & Ni is green

Group 17

HALOGENS

- Most reactive nonmetals because of high electronegativity

- Reactivity decreases down the group

-Fluorine is the most reactive nonmetal

- Always exist in diatomic form

-Sublimes?

Group 18

NOBLE GASES

- Gases

- Non reactive can be forced to react with Flourine

diatomic elements

Br, I, N, Cl, H, O, F

atomic radius

one-half the distance between the nuclei of two atoms of the same element when the atoms are joined

Hg and Br

2 elements that are liquids at room temperature