ionic bonding topic 4.1

http://www.youtube.com/watch?v=xTx_DWboEVs

http://www.youtube.com/watch?v=5IJqPU11ngY

Valence electrons› electrons in the highest occupied energy level › always in the s and p orbitals

normally just a draw a circle to represent these two orbitals

› determines the chemical properties of an element› usually the only electrons used in chemical bonds

http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_09/FG09_27-06un.JPG

IB may group levels together and therefore you would see the 3d10 before

the 4s2

IB uses this one

electron dot structures/diagrams are used to show valence electrons› each dot around the element symbol represents a

valence electron

B is 1s2 2s2 2p1;› 2 is the outermost energy level › it contains 3 valence electrons, 2 in the

s and 1 in the p Br is [Ar] 4s2 3d10 4p5

How many valence electrons are present?

http://images.google.com/imgres?imgurl=http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/imgper/econfig.gif&imgrefurl=http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/perlewis.html&h=267&w=512&sz=22&tbnid=__EXctBwlG0J:&tbnh=66&tbnw=128&hl=en&start=1&prev=/images%3Fq%3DElectron%2BDot%2BDiagrams%26svnum%3D10%26hl%3Den%26lr%3D

when forming compounds, atoms tend to achieve the electron configuration of a noble gas (ns2np6)› this means their highest energy level will be filled with

8 electrons the easiest way possible› atoms of metallic elements (groups 1,2,3) lose electrons

producing cations (positive ions) Ca becomes Ca2+

› atoms of nonmetallic elements (groups 5,6,7) gain electrons producing anions (negative ions) Cl becomes Cl1-

› group 4 can go either way often loose four electrons and become a 4+ cation

NeNeNNNaNa FF

NaNa+

OO

OO2-

MgMg

MgMg2+

Cations

Anions

NN3- FF1-

  ...etc.

As it turns out, atoms bond together for a very simple reason: atoms like

to have full valence shells.

1+ 2+ 3-3+ 4+/- 2- 1- 0

› transitional metals can often form more than one cation and therefore charges may vary

iron can be Fe2+ or Fe3+

may fill some orbitals but might not get a noble gas electron configuration

usually composed oppositely charged metallic cations and nonmetallic anions› because of the electrostatic attraction between oppositely

charged particles electro- electricity/electrons static- non-moving (vs. current which is moving charges)

form a compound with overall zero charge

+ cations

- anions

ions must have a difference in electronegativity of 1.7 or greater to form an ionic bond

0.1 – 1.0

1.1 – 1.7

>1.7

0.0 covalent, nonpolar

covalent, slightly polar

covalent, very polar

ionic

electronegativtydifference

probable type of bond

Na “gives” Cl one electron and now both atoms have a full valence shell (electron configuration of a noble gas)

3.9

Na Cl

e–1) 2)

3)

Na+ Cl–

shows the kinds and numbers of atoms in the lowest whole-number ratio of ions in the ionic compound› Na 1+ + Cl 1- NaCl

› Ca 2+ + Cl 1- CaCl2

› Mg 2+ + O 2- MgO

Mg and N? Mg2+, N3-

it takes two nitrogens to combine with three magnesiums› Mg3N2

› magnesium nitride

Na 1+ + F 1- NaF

high melting points can conduct electric currents when melted

or dissolved in water crystalline structure

› repeating arrays of cations and ions› an ionic lattice

cations lose valence electrons and therefore are positively charged› transition metals form more than one cation

with different ionic charges› charge is determined from the # of electrons

lost Fe2+ lost two electrons (the 2 in the 4s) Fe3+ lost three electrons (the 2 in the 4s and 1 in the 3d)

› naming Stock system

a Roman numeral is used to show the charge of the transition metal Fe2+ is iron(II) and Fe+3 is iron(III)

Naming Ions

› anions gain valence electrons and therefore are negatively charged change ending to –ide for the name

composed of more than one atom that form a single unit/ion with a charge› most end with -ite or –ate

the –ite ending indicates one less oxygen than the –ate ending ionic charge is the same for both

Memorize these!NO3

- nitrate

NO2- nitrite

OH- hydroxide

ClO2- chlorite

ClO3- chlorate

SO42- sulfate

SO32- sulfite

CO32- carbonate

HCO32- hydrogen

carbonate (bicarbonate)

PO43- phosphate

NH4+ ammonium

Binary Compounds› cation is written first, followed by the anion

with and –ide ending Cs2O cesium oxide

SrF2 strontium fluoride

CuO copper(II) oxide oxygen is always 2- and therefore copper will be 2+

Cu2O copper(I) oxide oxygen is 2- and therefore needed two copper atoms

with 1+ charge

› SnF2 ? fluorine is always 1- and therefore tin

will be 2+

tin(II) fluoride

› SnS2 ? sulfur is always 2- and therefore tin

will be 4+

tin(IV) sulfide

write symbol of cation and then anion add subscripts to balance the charges

› calcium bromide Ca2+ and Br1- is CaBr2

› potassium sulfide K+1 and S2- is K2S

› iron(III) oxide Fe+3 and O2- is Fe2O3

the ionic charge number of each ion is crossed over and becomes the subscript for the other ion

Fe(NO3)3

Choose the correct name for the compound

1. Iron trinitrate

2. iron(I) nitrate

3. iron(III) nitrite

4. iron(III) nitrate

5. none of the abovenext

problemPolyatomic

IonsPeriodic Chart

sodium chlorite

Choose the correct formula for the compound

1. NaCl

2. NaClO

3. NaClO2

4. Na(ClO)2

5. none of the above

next problem

PrefixesPeriodic Chart