Electron ArrangementElectron Arrangement

• Electrons are arranged in Electrons are arranged in energy energy levelslevels around the nucleus around the nucleus

• Each energy level can only hold a Each energy level can only hold a limited limited number of electronsnumber of electrons

• An atom will always fill the innermost An atom will always fill the innermost energy level before placing the eenergy level before placing the e-- in in the next energy levelthe next energy level(under normal conditions)(under normal conditions)

11stst energy level can hold up to energy level can hold up to

2 e2 e--

22ndnd & 3 & 3rdrd and so on can hold up to and so on can hold up to

8 e8 e--

Valence ElectronsValence Electrons

• The e- in the outer most levelThe e- in the outer most level

• They are important because they They are important because they determine HOW an atom acts towards determine HOW an atom acts towards other atomsother atoms

• They tell us the They tell us the number of electrons number of electrons that that will take place in bonding with other will take place in bonding with other atomsatoms

Chemical BondingChemical Bonding

BondingBondingCompounds are held together byCompounds are held together by

electrostatic attraction between + electrostatic attraction between + and -and -

charged atomscharged atoms

All atoms like to be…..All atoms like to be…..

HAPPYHAPPY

What is a happy atom?What is a happy atom?

• Any atom with a full VALENCE Any atom with a full VALENCE energy shellenergy shellIs this atom happy?Is this atom happy?

Is this atom happy?Is this atom happy? ??

Not only do they like to be Not only do they like to be happyhappyAtoms are also….. Atoms are also…..

LAZYLAZYExample:Example:

If an atom has If an atom has 11e in the outer shell,e in the outer shell,is it easier to FIND is it easier to FIND 77e to make it fulle to make it fullororis it easier to LOSE is it easier to LOSE 11e to make the e to make the previous energy level the outer shell?previous energy level the outer shell?

If an atom has If an atom has 33e in the outer shell,e in the outer shell,is it easier to FIND is it easier to FIND 55e to make it e to make it

fullfulloror

is it easier to LOSE is it easier to LOSE 33e to make e to make the previous energy level the outer the previous energy level the outer shell?shell?

Ionic Bonds:Ionic Bonds:Atoms will fill their outer level by Atoms will fill their outer level by

transfer transfer of their eof their e--

So……So……thethe loss loss or or gaingain of an of an electron causes an electron causes an unbalanced unbalanced

chargecharge

Atoms of unlike charges Atoms of unlike charges attractattract

Ionic bondIonic bond

Ionic bonds are betweenIonic bonds are betweenMetals + Non-metalsMetals + Non-metals

Covalent Bonds:Covalent Bonds:

Atoms will Atoms will shareshare outer most e outer most e-- to fill to fill each atoms outermost energy leveleach atoms outermost energy level

If covalent bonds are If covalent bonds are notnot shared equally, it is called a shared equally, it is called a

polar covalent bondpolar covalent bond

Covalent bonds are betweenCovalent bonds are betweenNon-metals + Non-metalsNon-metals + Non-metals

Practice…..Practice…..

When an atom gives up 1 or more When an atom gives up 1 or more electrons, what type of bond is it?electrons, what type of bond is it?

IONICIONIC

When an atom shares electrons, When an atom shares electrons, what type of bond is it?what type of bond is it?

COVALENTCOVALENT

IonsIons• If an atom is NOT electrically neutral If an atom is NOT electrically neutral

and has a positive or negative charge and has a positive or negative charge it is called an IONit is called an ION

• A positively charged ion is called A positively charged ion is called CATIONCATION

• A negatively charged ion is called an A negatively charged ion is called an ANIONANION