Periodic Characteristics

Valence electrons determine chemical & physical properties of the elements

Valence electrons – the electrons in the outermost energy level

Elements with the same number of valence electrons will have similar chemical properties.

Metals have shared properties because they lose electrons

Nonmetals have shared properties because they gain electrons

Periodic Characteristics

Ion – an atom that either loses or gains electrons

Metals tend to lose their valence electrons.

Losing electrons(negative charges) makes them positive

Cation – a positive ion Nonmetals tend to gain electrons

Gaining electrons makes them negative Anion – a negative ion

Ca ion+

a negative ion

Periodic Table Groups

The number of valence electrons determine the physical and chemical properties of the groupsGroup 1: Alkali Metals - Has only 1 valence electron - The most reactive metals - Not found in nature in pure form. Always in compounds

Videos: alkali metals in water

1

Periodic Table Groups

Group 2: Alkaline Earth Metals(two words, Group 2) - Has 2 valence electrons - Still very reactive - Not found in nature in pure form. Always in compounds

demo: magnesium & oxygen

2

Periodic Table Groups

Groups 3 through 12: Transition Metals - Valence electrons vary - metals can form multiple cations (Cr2+,Cr3+,Cr7+) - compounds are brightly colored - Group 11 is least reactive

demo: colored compounds

3 4 5 6 7 8 9 10 11 12

Periodic Table Groups

Group 14: aka Carbon Group - Has four valence electrons - carbon has three allotropes: coal, diamond, graphite - Allotrope: substances made from the same element, but with different physical and chemical properties

1415

Group 15: Nitrogen Group - Has five valence electrons

• *note- bottom element is a metal!*

Periodic Table Groups

Group 16: Oxygen Group 6 valence electrons oxygen has 2 allotropes:

O2 (air) & O

3(ozone)

Group 17: The Halogens “salt-forming” 7 valence electrons most reactive nonmetals

Most are diatomic(2 atoms): diatomic - compounds made with two atoms of the same element.

1617

- Other diatomic elements: Hydrogen, Oxygen & Nitrogen. - Together, they form BrINClHOF: Bromine(Br

2) Iodine(I

2),

Nitrogen(N2), Chlorine(Cl

2), Hydrogen(H

2), Oxygen(O

2), and

Fluorine(F2)

Periodic Table Groups

Group 18: The Noble Gases - 8 valence electrons(except helium which has 2) - full outer shell (aka filled principal energy

level) - chemically unreactive

Lanthanides contain the rare earth metals Many used in modern electronics

Actinides some are man-made all are radioactive & decay over time

18

Lanthanides →

actinides →

Electron Configuration &The Periodic Table

Think back to electron configuration- Electrons are arranged in energy levels Energy levels are made up of orbitals: s, p, d & f s can hold 2 electrons, p can hold 6, d holds 10,

f holds 14

The Periodic Table can tell us what orbital is being filled by the atom's location on the Periodic Table.

P.T. & Electron Configuration

The Periodic Table is sorted by the location of valence electrons in the electron configuration

s-block : Electron configuration ends with s¹ or s²

p-block : Electron configuration ends with p1 through p6

d-block : electron configuration ends with d1 through d10

Atoms in the d-block often form multiple cations. f-block: electron configuration ends with f1 to f14

Blocks

s-b

lock

p-blockd-

block

f-block

Average Isotopic Atomic Mass

**The Atomic masses in the Periodic Table are not mass numbers.** They are an average of all the isotopes of that element, weighted by abundance.

·

Rounding the ave. atomic mass in the P.T. usually gives you the most common

isotope. For iron (mass 55.847 amu in P.T.) the most common isotope is iron-

_________56