Periodicity
Metals, nonmetals, & metalloids
Transition metals vs. representative elements
1
2
3
4 5
6
7
Groups of Elements Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases
Trends in the periodic table
Groups (families) They all have the same # of outer electrons=
VALENCE ELECTRONS
Periods They have valence electrons in the same
highest energy level
Periodic trends Periodic = happens according to a repeating
pattern Periodic table has repeating pattern of
valence e- configurations Leads to periodic trends:
Atomic Radius Ion Formation and Ion size Ionization Energy Electronegativity
Periodic trend: Atomic Radius Size of atoms depends on:
Number of energy levels
Number of protons
Down a column: Across a row:
What is the trend across a period?Atomic Radii of Periods 1-3 of the Periodic Table
H
He
Li
Be
B
CN O F
Ne
Na
Al
SiP
SCl
Ar
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 2 4 6 8 10 12 14 16 18 20
Atomic Number
Ato
mic
Ra
diu
s (
10-9
m)
A closer look at the trend across a period.Atomic Radii of Period 4 of the Periodic Table
0.1
0.12
0.14
0.16
0.18
0.2
0.22
0.24
16 21 26 31 36
Atomic Number
Ato
mic
Rad
ius
(10-9
m)
What is the trend down a group?
Atomic Radii of Group 2
Be
Mg
CaSr Ba
0
0.05
0.1
0.15
0.2
0.25
0 10 20 30 40 50 60
Atomic Number
Ato
mic
Rad
ius
(nm
)
Atomic radius increases down a group. The number of energy levels increases down a group Each subsequent energy level is further from the
nucleus .n=1
n=2
n=3
n=4
n=5
Atomic radius decreases across a row
Across a row valence electrons are in the same energy level (n=3)
Positive charge of nucleus is partially cancelled out by negative charge of core electrons =electron shielding
With each additional proton, there is a stronger force pulling the electrons closer to the nucleus. This results in a smaller atomic radius.
Electron shielding in Na vs. Cl
Shielding
Which has the greater atomic size, C or O?
Which has the greater atomic size, Li or K?
Ionization energy (kj/mol)
Recall emission lab…..
Ionization energy – the energy required to remove an electron from an atom. (pg. 358)
Ionization Energy- what is the trend?
Ionization Energy Periods 1-3
H
He
Li
BeB
C
NO
F
Ne
Na
MgAl
Si
SP
Cl
Al
0
500
1000
1500
2000
2500
0 2 4 6 8 10 12 14 16 18 20
Atomic Number
Ion
izatio
n E
nerg
y (kJ/m
ol)
Ionization Energy
Can you explain this trend? Click HERE for a tutorial.
Ionic Radii What happens to the size of the atomic radius
when an electron is removed?
Is an anion bigger or smaller than its neutral atom? Why?
Radii of neutral and charged atoms in pm (10-12m)
Purple models represent neutral atoms; Red=cations; Blue=anions
Check your understanding Which atom would be larger, and why?
N or O K or Rb Ne or Na
Which atom would be more difficult to turn into a cation (higher IE), and why? Li or Be Mg or Ca F or Ne
Electronegativity Electronegativity – is the ability of an atom to
ATTRACT electrons when the atom is in a compound. (pg 363)
Credit to Linus Pauling
Ionization & Ionic Compounds
Unit 3 • Chemistry 1 • Spring 2012
What’s an ion? Ion =
Cation Anion
Atoms form ions when they are able to give away or accept electrons.
The most likely type of ion an atom will form is based on the number of valence electrons it starts with.
Comparing cations and anionsCations Positive charge Valence e- removed Size vs. atom:
NaNa+
CuCu2+
Anions Negative charge Valence e- added Size vs. atom:
OO-
O2-
Ionization-how does it happen? How do ions form?
Will it be endothermic or exothermic?
What happens next?
Specific ions form for each element due to its electron configuration
Elements with electrons that completely fill the s and p orbitals of the highest energy level do not react.
Elements without “full” outer energy levels take, give up, or share electrons (chemical bonding).
Vocabulary: OCTET RULE ISOELECTRONIC
Cation formation How many valence electrons does Na have? Would Na give up its valence electron
spontaneously? Why does Na tend to form an Na+ cation,
rather than an Na2+ (or any other) cation?
What about Mg? What about F?
Anion formation How many valence electrons does F have? Is it possible to add an extra electron into the valence
energy level of F? Why does F tend to form an F- anion, rather than an
F2- (or any other) anion?
What about O? What about Be?
Electron configurations Write the electron configuration for each
neutral atom. What ion will form for each? F
O
Li
He
Ne
Cl
Symbols for ions: Use the chemical symbol and the charge for
each ion. Notice PT trends!
Some common ions
Periodic relationship of simple ions
Transition Metals?
Ionic bonding
Oppositely charged ions attract!
This forms a strong electrostatic attraction Called an Ionic Bond.
Atoms will become charged before making ionic bonds Ion
charged atom loss or gain of electrons
Cations: Anions:
(fulfills octet or duet rule)
Use periodic table to predict the ion formed for O, Li, He, Ne, and Cl
Ionic bonds-form a crystal lattice Ions form ionic crystals.
pattern of alternating + and – ions
An exothermic process.
Crystal structure extremely stable.
Click HERE for an animated tutorial
Ionic Solids
Salts are held together by ionic bonds
Ionic compounds When cations and anions come together to
form ionic bonds, an ionic compound is the result.
All compounds are neutral. Ex: Na reacts with S
Ionic Compounds Most ionic compounds are composed of a metal and
a nonmetal. Example: Sodium Chloride Example: Magnesium Oxide
Are ionic compounds charged?
Ionic compounds are NEUTRAL (no charge), so the two ions together must cancel each other’s charge. Example: Mg+2 and O-2 or Na+ and Cl-
One of each ion, makes a neutral ratio.
Ionic Compounds What if the ions are of different charges?
Example: Sodium and Oxygen Na+1 and O-2
The ions exist in ratios, producing an electrically neutral compound. 2 sodium ions for every oxygen ion
How can we write this as a formula? Na2O This formula shows NO charges, it is neutral There are two sodium ions for every oxygen It represents a RATIO of ions.
Practice writing formulas for the following ionic compounds:
potassium fluoride
calcium bromide
aluminum chloride
sodium sulfide
beryllium oxide
Formulas of ionic compounds potassium fluoride
KF calcium bromide
CaBr2
aluminum chloride AlCl3
sodium sulfide Na2S
beryllium oxide BeO
Rules for naming ionic compounds Salts (ionic compounds) are named:
Cation first, anion second. Cations are named the same as the neutral
atom, i.e. sodium, aluminum… they almost always end
in “-ium”. Anions are named with the ending “-ide”.
i.e. fluorine fluoride; oxygen oxide Examples: sodium chloride, magnesium oxide
Ions of transition metals Some transition metals can form more than one ion Roman numerals indicate which it is. Example:
Name: Nickel (I) oxide: Ions: Ni+1 and O-2
Formula: Ni2O
Example: Name: Cobalt (II) Chloride Ions: Co+2 and Cl-1
Formula: CoCl2
Roman numeral exceptions Some transition metals only form one stable ion and do
not require roman numerals: Ag+ Zn+2
A few other metals have more than one stable ion and require roman numerals: tin(II) and tin(IV) lead(II) and lead(IV)
Memorize these...
Practice writing names for ionic compounds of transition metals ZnCl2
PbBr2
AuO
Names of ionic compounds ZnCl2
zinc chloride
PbBr2
lead (II) bromide
AuO gold (II) oxide
Polyatomic ions: to memorizePolyatomic ion Name:
SO4
-2 sulfate
NO3-1 nitrate
CO3-2 carbonate
HCO3-1 bicarbonate
NH4+1 ammonium
OH-1 hydroxide PO4
-3 phosphate
CH3COO-1 (C2H3O2 -1) acetate
Formulas for ionic compounds: Iron(II) phosphate
Zinc carbonate
Aluminum nitride
Formulas for ionic compounds: Iron(II) phosphate Fe3(PO4)2
Zinc carbonate ZnCO3
Aluminum nitride AlN
Naming ionic compounds: MgSO4
Cu(OH)2
NH4Cl
Naming ionic compounds: MgSO4 magnesium sulfate
Cu(OH)2 copper(II) hydroxide
NH4Cl ammonium chloride
Introducing dimensional analysis. Suppose you work at a hardware
store and a customer comes in asking to buy 150 bolts from a bulk bin. What would be the most efficient way to get the customer his 150 bolts.
Counting large numbers
Atoms are too small to count one at a time!
The “mole” is a useful unit for counting atoms or other small particles.
1 mole = 6.022 x 1023 objects
Compare and contrast
Compare 5 dozen bagels to 5 dozen elephants How are they the same? How are they different?
Compare 2.5 moles of hydrogen atoms to 2.5 moles of gold atoms How are they the same? How are they different?
Avogadro’s Number
Ratio between grams and a.m.u.
Therefore, atomic masses on PT are also the molar masses of elements (in g/mol)
Counting by weighing We know the mass of 1 mole of any element
AND
We know how many atoms are in 1 mole of any element
THEREFORE we can “count” a certain number of atoms using mass.
Molar mass of compounds
To calculate the mass of one mole of a compound, add the molar masses of the atoms
EX: 1 mole of Al2O3 has 2 mol Al + 3 mol O
What is the molar mass of: Li3P NaOH Mg(NO3)2
Mole ratios for compounds
One mole of CaCl2 has mole(s) of Ca2+ ions mole(s) of Cl- ions
One mole of Al2(CO3)3 has mole(s) of Al3+ ions mole(s) of CO3
2- ions
Examples:
What is the mass of 1 mole of calcium atoms? What is the mass of 2 moles of calcium
atoms? What about 5.3 moles?
How many atoms are there in 2.25 moles of sulfur? What is the mass of this sample?
Conversion blueprint
Atoms (particles)
Moles Mass (g)
Calculations with ionic compounds
How many moles in 5000 kg of iron(III) oxide?
What is the mass of 2.50 mol of calcium chloride?
How many potassium ions are there in 4.5 moles of potassium oxide?
How many formula units are there in 285 g of copper(II) oxide?
Test Preparation: Start the review sheet…but don’t end there. Use practice problems from the book at the end of
the chapter. Power point DO PRACTICE PROBLEMS! Do the worksheets or
look over labs again. Be able to explain ideas completely. Cause and
effect.