The Modern Periodic Table

Trends

Agenda

• Lesson: PPT,

• Handouts: 1.PPT Handout; Periodic Table Puzzle; Periodic Table Worksheet

• Text: 1. P. 30-33; Organization of the periodic table

• HW: 1. P. 33 # 1-4, 6; Finish all the worksheets

The Modern Periodic Table

1. An arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column (or group).

• Groups: vertical columns (#1-18)

• Periodic: horizontal rows (# 1-7)

2. Periodicity – the similarities of the elements in the same group is explained by the arrangement of the electrons around the nucleus.

The s-block Elements: Groups 1 ns1

1. Group 1: Alkali metals

• soft silvery metals

• most reactive of all metals, never found free in nature

• reacts with water to form alkaline or basic solutions

store under kerosene

• whenever you mix Li, Na, K, Rb, Cs, or Fr with water it

will explode and produce an alkaline solution

• ns1 (ending of all electron configurations for this group)

The s-block Elements: Group Alkaline earth metals- ns2

• less reactive than Alkali, but still react in water to

produce an alkaline solution

• never found free in nature

• harder, denser, stronger than alkali

• ns2 (ending of all electron configurations for this

group), because they have 2 electrons in the s sublevel, this makes them a little less reactive then the Alkali metals in group 1.

The d-Block Elements: Groups 3-12

• are all metals with metallic properties (malleability,

luster, good conductors, etc…); are referred to as the

Transition Metals

• Harder and denser than alkali or alkaline

• Less reactive than alkali or alkaline

• For the most part their outermost electrons are in a

d sublevel

• Exceptions to the electron configuration are found in

these groups (Ex: Ni, Pd, Pt)

The p – Block Elements: Groups 13 – 18 -np

• Contain metals and nonmetals

• Metalloids, along zigzag line, have characteristics of

both metals and nonmetals (many are good conductors

but are brittle). The metalloids are boron, silicon,

germanium, arsenic, antimony, and tellurium.

Group 17 - Halogens – most reactive nonmetals-np5

• 7 electrons in outermost (s and p) energy levels (that is why so reactive – only need one electron to have 8)

• called the salt formers (they react vigorously with metals to form salts). A salt is a metal and a nonmetal bonded together.

• most are gases

Group 18 - Noble gases –unreactive-np6

• 8 electrons in outermost s and p energy levels

• all are gases

• The s and p blocks are called the main group or representative elements!

The f-Block Elements: Inner Transition Metals

• final electrons fill an f sublevel

• Lanthanides – shiny reactive metals; Ce-Lu (fill the 4f sublevel)

• Actinides – unstable and radioactive; Th-Lr (fill the 5f sublevel)

Hydrogen and Helium - Oddballs

• Hydrogen is NOT an Alkali metal, it is a very reactive gas. It is placed with the Alkali metals because 1s1 is its electron configuration.

• Helium is a Noble gas, it is unreactive, but it does not have 8 electrons in outermost energy level, because it only has 2 total electrons!

# of Valence

Electrons Group # Ending Configuration

1 1 ns1 very reactive

2 2 ns2

3 13 np1

4 14 np2

5 15 np3

6 16 np4

7 17 np5 very reactive

8 18 np6 very unreactive

Agenda

Trends- Definitions

• Lesson: PPT

• Handouts: 1. Propeties of Atoms,

• Text: 1. P. 36-41-Trends parameters and definitions

• HW: 1. Finish all the worksheets

Graphing Assignment

ATOMIC RADIUS • Atomic radius is the distance from the centre of the

nucleus of an atom to the outermost electron. • The greater the number of energy levels the greater

is the distance of the outermost electron to the center of its atom’s nucleus.

• Ionic radius is the distance from the centre of the

nucleus of an ion to the outermost electron. Cations will have a smaller ionic radius than the neutral atom. Anions will have a larger ionic radius than the neutral atom.

FORCE OF ATTRACTION

• The force of attraction between negatively charged electrons and the positively charged nucleus is the electrostatic attraction of opposite charges. • The force of attraction existing between the outermost electron and the middle of the nucleus is dependent on two factors: 1. The size of the positive charge - determined by the number of protons in the nucleus. 2. The distance between the outermost electron and the nucleus. • A balance exists between the attraction of the electrons to the nucleus and the repulsion of the electrons between themselves

Trend in Atomic Radii

The size of an atomic radius cannot be measured exactly because it does not have a sharply defined boundary. However the atomic radius can be thought of as ½ the distance between the nuclei of identical atoms joined in a molecule.

Group trend - atomic radii decrease as you move up a

group.

Period trend – atomic radii decrease as you move across a period.

Atomic Radii Trend

Example: Which is larger? P atom or Cl atom

Example: Which would be larger? K+1 or K

Example: Which would be larger? K+1 or Ge+4

Graphing Assignment

Ionization Energy (IE) • Ionization Energy is the energy in kilojoules per mole

(kJ/mol) needed to remove the outermost electron from a gaseous atom to form a positive ion (cation) Na + Energy Na+ + e-

• neutral sodium has 11 protons and 11 electrons

• removal of 1 electron leaves 10 electrons and 11 protons and a net imbalance of charge of +1

NOTE: Metals react to lose electrons

The stronger an electron is held the greater the IE needed to ionize (pull away) that electron

Successive Ionization Energy

• After the outermost electron (First IE) is removed the successive ionization energies (Second and Third IE and so on) increase as it becomes more difficult to remove the next electrons since the pull of the nucleus becomes stronger and electrons are more tightly held.

Trend: Ionization Energy (IE) Group trend – ionization energy increases as you move

up a group (or decreases as you move down a group).

Period trend – ionization energy increases as you move

across the period.

IE Trend

Highest Which atom has the higher first ionization energy? (A) Hf or Pt Pt (B) Cl or Ar Ar

ELECTRON AFFINITY [EA]

• Electron affinity is the energy released in kilojoules

per mole (kJ/mol) when an electron is captured by an atom to form a negative ion (anion)

Cl + Electron Cl- + Energy

• neutral chlorine has 17 protons and 17 electrons

• addition of 1 electron gives 18 electrons and 17 protons and a net imbalance of charge of -1

• NOTE: Nonmetals react to gain electrons

Trend: Electron Affinity (EA) Period trend – electron affinity increases as you move across a period because atoms become smaller and the nuclear charge increases. This means there is a greater pull from the nucleus. Group trend – electron affinity increases as you move up a group (or decreases as you move down a group) because the size of the atom increases. Example: Which element has the greater electron affinity? Pb or Sn Sn

EA Trend

Highest

Electron affinity vs. Ionization energy

Electron affinity and Ionization energy follow the same trend in the periodic table.

• The stronger the attraction an atom has for electrons the harder it will be to remove electrons from that atom and the higher the IE energy will be.

• The greater the attraction for electrons the greater the energy released when an atom gains an electron.

ELECTRONEGATIVITY [EN] • Electronegativity is a measure of the tendency of an

atom to gain electrons when it is chemically combined (bonded) to another element.

• The stronger the ‘pull’ or attraction of electrons to an atoms nucleus, the greater its tendency to gain electrons

In general, metals have low EN and nonmetals have high EN. The actual amount of EN an atom has is indicated by a number of the Pauling Electronegativity Scale that goes from 0 to 4. Dr. Linus Pauling set up this scale and gave the element having the greatest EN an arbitrary number of 4, and he assigned numbers to the others relative to this element.

Trend: Electronegativity (EN) Period trend - EN increases as you go across a period

(excluding the noble gases) because size decreases.

Group trend - EN increases as you go up a group because

there is less pull from the nucleus as the electrons get

further away.

Example

• Which would have the greater

EN? Ca or Se

Se Electronegativity enables us to predict what

type of bond will be formed when two elements

combine.

Electronegativity Trend

Highest

Electronegativity Chart

Electronegativity Chart

Electronegativity Chart

Agenda

• Expanations of Trends and Summary

• Lesson: PPT

• Handouts: 1. Propeties of Atoms, 2. Trends in the Periodic Table Summary Sheet

• Text: 1. P. 36-41-Trends parameters and definitions

• HW: 1. P. 41 # 1-7; 2. Finish all the worksheets

Reactivity of Nonmetals Reactivity -how easily a substance reacts with another

• Nonmetals gain electrons ( Electron Affinity)

• Metals lose electrons ( Ionization Energy)

Nonmetal Reactivity

Trend

Highest Metal Reactivity

Trend

Highest

TRENDS IN THE PERIODIC TABLE - SUMMARY SHEET

NAME DEFINITION TREND EXPLANATION

ATOMIC RADIUS

Distance measured from the centre of the nucleus to the outermost e_ in pm or Ao

1. Increases down a group 2. Decreases across a period from left to right

1. Increase in no. of energy levels and electrons -more repulsion 2. e- held more tightly, increase in ENC, less shielding smaller radius

NAME DEFINITION TREND EXPLANATION

FIRST

IONIZATION ENERGY

Energy required to remove the outermost electron from a gaseous atom

1. Decreases down a group 2. Increases across a period from left to right

1. Increase in radius due to more energy levels ,electrons less tightly held 2. e- held tightly, increase in ENC less shielding , harder to remove e-

NAME DEFINITION TREND EXPLANATION

ELECTRON AFFINITY

The energy given off (released) when an atom gains an e-

1. Increases up a group 2. Increases across a period from left to right not including Group 18

1. Fewer energy levels, small atomic radius ... greater attraction of electrons 2. Greater ENC, greater attraction for electrons, less shielding

NAME DEFINITION TREND EXPLANATION

ELECTRO-NEGATIVITY

The tendency to gain electrons

1. Increases up a group 2. Increases across a period from left to right not including Group 18

1. Fewer energy levels, small atomic radius ... greater attraction of electrons 2. Greater ENC, greater attraction for electrons, less shielding

NAME DEFINITION TREND EXPLANATION

REACTIVITY METALS

The degree to which metals have a tendency to react with other substances by losing electrons

1. Increases down a group 2. Decreases across a period from left to right

1. More energy levels, larger atomic radius ... weaker attraction of e- -electrons more easily removed 2. Lower ENC, weaker attraction for e-, less shielding, more easily removed

NAME DEFINITION TREND EXPLANATION

REACTIVITY NONMETALS

The degree to which nonmetals have a tendency to react with other substances by gaining electrons

1. Increases up a group 2. Increases across a period from left to right not including Group 18

1. Fewer energy levels, smaller atomic radius ... greater attraction of electrons 2. Greater ENC, greater attraction for electrons, less shielding smaller atomic radius

Effective Nuclear Charge

Group Number

1 2 13 14 15 16 17 18

Element Na

Mg Al Si P S Cl Ar

# of electrons

# of valance electrons

# of protons

# of inner electrons

ENC

Effective Nuclear Charge

Group Number

1 2 13 14 15 16 17 18

Element Na

Mg Al Si P S Cl Ar

# of electrons 11 12 13 14 15 16 17 18

# of valance electrons

1 2 3 4 5 6 7 8

# of protons 11 12 13 14 15 16 17 18

# of inner electrons

10 10 10 10 10 10 10 10

ENC

Effective Nuclear Charge

Group Number

1 2 13 14 15 16 17 18

Element Na

Mg Al Si P S Cl Ar

# of electrons 11 12 13 14 15 16 17 18

# of valance electrons

1 2 3 4 5 6 7 8

# of protons 11 12 13 14 15 16 17 18

# of inner electrons

10 10 10 10 10 10 10 10

ENC 1 2 3 4 5 6 7 8

ENC = Number of Protons – Number of Inner Electrons

EFFECTIVE NUCLEAR CHARGE AND SHIELDING

• The force of attraction between positively charged protons in the nucleus and negatively charged electrons is the force that holds atoms together.

• The inner electrons (not in the outermost energy level) in

inner energy levels, partially block or shield the attraction of the protons from the outer electrons in the outermost energy level (VALENCE ELECTRONS).

• The canceling of the positive nuclear charge is called

SHIELDING EFFECT.

EFFECTIVE NUCLEAR CHARGE (ENC)

• EFFECTIVE NUCLEAR CHARGE (ENC) is a number assigned to elements to describe the amount of shielding felt by the valence electrons.

ENC = Number of protons - Number of inner electrons • The greater the ENC the less the valence electrons are shielded and

the stronger the pull on the valence electrons. • Greater ENC will mean a smaller atomic radius. • Shielding will help explain some of the trends in the periodic table

Agenda

Successive Ionization Energies

• Lesson: PPT- Take up of all the problems

• Handouts: 1. Properties of Atoms, 2. Trends in the Periodic Table Summary Sheet

• Text: 1. P. 36-41-Trends parameters and definitions

• HW: 1. Finish all the worksheets 2. P 47 1-18; P. 48 #1-19,31; P. 48 # 47,55-57,65-69.

SUCCESSIVE IONIZATION ENERGIES • The first ionization energy is the energy required to

remove the outermost electron (First IE). It is relatively low because of the repulsion exerted by the other electrons

• Each successive ionization energy (Second and Third IE and so on) will increase.

• It becomes more difficult to remove successive electrons since the pull of the nucleus becomes stronger (greater number of protons relative to the electrons) and the electrons are more tightly held

Ionic radius becomes smaller • There will be a noticeable jump in the increase of IE

once the noble gas configuration has been reached

This is because outer energy level has been removed ( radius is smaller)

Successive Ionization Energies

Example 1: Consider the following Ionization Energies for an element X:

How many valance electrons does this element have?

1st 2nd

3rd

4th 5th

2.38 kJ 2.54 kJ 22.48 kJ 25.88 kJ 28.35 kJ

ANS:

The element has 2 valence electrons. Removing the third electron from X 2+ involves a much greater energy. The third electron is closer (one energy level closer) to the attracting nucleus since the noble gas configuration has been reached.

Example 2: Where would the large increase in I.E. occur for Se? Explain your answer.

The large increase would occur going form 6th to 7th IE. There is a noticeable jump in increase of I.E. since the noble gas configuration has been reached.

(Se 6+) 1s2 2s2 2p6 3s2 3p6