Chemistry

Chapter 8Notes #1

Ions

Compounds

2 or more elements combined Example: Sodium + Chlorine = Sodium

Chloride (which is table salt) A compounds properties are different from the

properties of the individual elements that make it up

Compounds can be represented by chemical formulas

Ex. NaCl (salt)

Compounds Compounds are held together by chemical

bonds Attractive forces that hold atoms or ions

together Ionic (referred to as formula units)Metallic Covalent (referred to as molecules)

Valence Electrons …

The electrons responsible for the chemical properties of atoms, and are those in the outer energy level.

Valence electrons - The s and p electrons in the outer energy level the highest occupied energy level

Core electrons –the inner electrons (those in the lesser energy levels)

Valence Electrons … Atoms in the same column...

Have the same outer electron configuration.

Have the same valence electrons. The number of valence electrons are

easily determined: the group number for a representative element

Group 2A: Be, Mg, Ca, etc. have 2 valence electrons

Electron Dot diagrams … A way of showing & keeping

track of valence electrons. How to write them? Write the symbol - it

represents the nucleus and inner (core) electrons

Put one dot for each valence electron (8 maximum)

They don’t pair up until they have to (Hund’s rule)

X

Electron Dot diagrams …

Nitrogen has 5 valence electrons to show.

First we write the symbol. NThen add 1 electron at a time to each side.Now they are forced to pair up.

We have now written the electron dot diagram for Nitrogen.

Stable Electron Configurations

All atoms react to try and achieve a noble gas configuration.

Noble gases have 2 s and 6 p electrons. 8 valence electrons = already stable! This is the octet rule (8 in the outer level is

particularly stable).

Ar

Ions Ions – atoms that have lost or gained

valence electrons, resulting in an overall charge

They lose or gain to meet the octet rule Cations – positive ions (loss of electrons)

Metals form positive ions Anions – negative ions (gain of electrons)

Nonmetals form negative ions

Cations

Form when metals lose electrons Trying to meet the octet rule-Achieve a noble gas

configuration Ex. Sodium (Na) becomes Na+

Loses its 1s electron- Then has the same electron configuration as Neon

Cations

calcium has only 2 valence electrons It’s easier to lose 2 than gain 6

Ca Ca+2

Cations Example

Magnesium = 1s22s22p63s2

Mg+2 = 1s22s22p6

Neon = 1s22s22p6

Drawings

cations

Cations Transition Metals

Most of the time will have a +2 or +3 charge

They lose both electrons from their outermost s sublevel

Then, they can also lose inner unpaired d sublevel e-

Which leads to a charge of more than +2 Pseudo noble gas configurations (Non octets with stability)

Example: A pseudo-noble gas configuration is: 1s2 2s2 2p6 3s2 3p6 3d10 (and they have 2 in 4s)

This is found in Cu+ Zn2+ Ga3+ and Ge4+

Anions

Nonmetals will have many valence electrons (usually 5 or more)

They will gain electrons to fill outer shell.

P P3-This is called the phosphide ion

Electron Configurations for Anions Example

Oxygen = 1s22s22p4 O-2 = 1s22s22p6

Neon = 1s22s22p6

Drawings

Oxygen

Ions

Polyatomic Ions Al individual elements that have lost or

gained electrons are monatomic ions Binary compound – 2 monatomic ions

combine Oxidation Number – the charge of the ion Polyatomic ions – a group of more than 1

atom that loses and gains electrons They act like an individual ion Have one charge (as a unit) Oxyanions = polyatomics with oxygen