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MetalsMetalsExtra electronsExtra electronsConductiveConductiveMalleableMalleable

DenseDenseShinyShinyDucti leDucti le

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Metal an atom with 1-3 extra valence electrons.

Shiny Dense Malleable Ducti le Electrical conductors Thermal conductors

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In 1817,German scientist named Deboreiner realized that there's is a connection between relative atomic mass and chemical properties

In 1829,he arranged many elements into group of three, called Deboreiner’s triads in which the relative mass of the middle element about the average of masses of the other two. However only few elements form the group of three.

In 1864, the British scientist called Newlands, Arranged elements in order of relative atomic mass and gave each one number, Hydrogen the lightest element was no. 1, lithium 2, helium was not known at that time and so on.

He was the first scientist to list elements in numerical order. BUT his law didn’t apply after 17 elements (Ca).

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In 1869 Mendeleef, a Russian scientist, stated that the properties of element are a periodic in function of their atomic masses.

This periodic law means that if the elements are arranged in order of increasing their relative mass, element of similar properties appear in regular intervals . This kind of repetition is periodic

Mendeleef ‘s periodic table was in complete because many elements (e.g. noble gases were not known that time.

In 1913 an English research student called Moseley. He found that atomic number is more important than the relative atomic mass and that there is no exceptions in periodic table

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Periodic Table of an element Is the arrangements of elements in order of their proton numbers,

Horizontal raw are period and the vertical column are groups  Characteristics of Periodic Table There are 8 groups and 7 periods Period 1 contain only Hydrogen and Helium. Hydrogen is placed both in

group one and group 7 because its properties resembles of those of alkali metals and halogens

Period 2 and 3 (Short periods) contains 8 element each Period 4 and 5 ( Long periods) each contains 18 elements. 8 elements

of these correspond to the 8 element in the short period. The other 10 are called transition elements . Which show similar properties before them and also some properties similar to those following them.

Period 6 and 7 contain 32 and 17 elements

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Periodicity of properties of the element. Physical properties. Physical properties of elements in the same group vary gradually and regularly. All group one alkali metals have low densities, low melting point and high

conductivities. In group 7 halogens, The melting points, boiling points and the densities rise

regularly. The first member of the group e.g lithium and fluorine is usually slightly different form the rest of the group)

  Chemical properties.  Vary gradually for the same group of elements. Of the alkali metals potassium is more electropositive than sodium which is more

electropositive than lithium. Of halogens fluorine is most electronegative metals and iodide is least. Metals are on the left hand side of the table and non metals are on the right. In group 1 metals are reactive as their relative atomic mass increases. In group 7 the halogen are less reactive when their masses increase.

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Famil ies of elements. The periodic table is accounted for the regular

arrangement of electrons in atoms of elements. The periodicity of electron configuration leads to periodicity of chemical properties which depends on configuration of the outermost orbit.

 

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Noble gasses configuration. The outer most shell of electron with two electrons

in case of helium and eight for other elements Are very stable and the electrons are not used in

chemical reactions. The noble gasses are very un reactive. Noble gas

elements are Ne (2:8) Ar (2:8:8)

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Noble (inert) GasesNoble (inert) Gases Group #8 atoms Group #8 atomsP shell ful l P shell ful l Very non-reactive Very non-reactive VERY happy VERY happy

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 GROUP 1 & 2 METALS.  An alkali metal atoms◦ Has one electron more than noble gas structure. The electron is readity detached and the element

are therefore very electropositive . These include: Li (2:1) Na,(2:8:1) K, (2:8:8:1)   Alkali earth metals◦ Have two electrons more than noble gas these can readity be detached and the metals are

electropositive. Examples of alkal earth metals are Be (2:2), Mg (2:8:2), Ca, (2:8:8:2) They show relative weak metalic bonding because they have only one metalic bonding. They are soft, can be cut with knife. BP and MP are low. Low standard heat enthalples Low densities. Group 2 with two valence electron they show stronger metalic bonding.

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periodic trends are the tendencies of certain elemental

characteristics to increase or decrease as one progresses along a row or column of the periodic table of elements.

Elemental characteristics in periodic table are Atomic radius Electronegativity Ionization energy Metallic characters

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The atomic radius is the distance from the atomic nucleus to the outermost

stable electron orbital in an atom that is at equilibrium. The atomic radius tends to decrease as one progresses

across a period because the effective nuclear charge increases, thereby attracting the orbiting electrons and lessening the radius.

The atomic radius usually increases while going down a group due to the addition of a new energy level (shell). However, diagonally, the number of protons has a larger effect than the sizeable radius. For example, lithium (145 pm) has a smaller atomic radius than magnesium (150 pm).

Atomic radii decrease left to r ight across a period, and increase top to bottom down a group.

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• Atomic Radius• size of atom

© 1998 LOGAL• Ionization Energy• Energy required to

remove one e- from a neutral atom. (gaseous state)

© 1998 LOGAL

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0

50

100

150

200

250

0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)

Li

ArNe

KNa

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1

2

3

4 5

6

7

• Increases going down and Decreases going right.

Decreases!Increases

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• Why larger going down?

• Higher energy levels have larger orbitals

• Shielding - core e- block the attraction between the nucleus and the valence e-

• Why smaller to the right?

• Increased nuclear charge without additional shielding pulls e- in tighter

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• Ionic Radius

• Cations (+)• lose e-

• smaller

© 2002 Prentice-Hall, Inc.

• Anions (–)• gain e-

• larger11/05/14 19

Effective nuclear charge concept The shielding effect that electrons close to the nucleus

have an outer shell of an electrons in many electrons atoms.

The presence of shielding electrons reduces the electrostatics attraction between the positively charged protons in the nucleus and the outer electrons.

Moreover, the repulsive forces between the electrons in many electrons atom further offset the attractive force exerted by the nucleus the concept of effective nuclear charge

Effective nuclear charge increases from left to right across the period and from the bottom to top in a group of representative elements

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Ionization energy is the minimum energy required to remove one electron from each

atom in a mole of atoms in the gaseous state. Trend-wise, ionization potentials tend to increase while one

progresses across a period because the greater number of protons (higher nuclear charge) attract the orbiting electrons more strongly, thereby increasing the energy required to remove one of the electrons.

As one progresses down a group on the periodic table, the ionization energy will likely decrease, since the valence electrons lie are farther away from the nucleus and experience a weaker attraction to the nucleus' positive charge.

There wil l be an increase of ionization energy from left to r ight of a given period and a decrease from top to bottom .

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0

500

1000

1500

2000

2500

0 5 10 15 20Atomic Number

1st

Ion

izat

ion

En

erg

y (k

J)

KNaLi

Ar

NeHe

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1

2

3

4 5

6

7

• Decreases going down and Increases going right.

Increases!Decreases

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• Why opposite of atomic radius?• In small atoms, e- are close to the nucleus where the attraction is stronger, therefore they are more difficult to remove

• Which family has the highest IE and why?

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Electron affinity Electron affinity of an atom can be described either as the energy gained by an

atom when an electron is added to it, or conversely as the energy required to detach an electron from a singly-charged anion.

The sign of the electron affinity can be quite confusing, as atoms that become more stable with the addition of an electron (and so are considered to have a higher electron affinity) show a decrease in potential energy; i.e. the energy gained by the atom appears to be negative.

As one progresses from left to right across a period, the electron affinity value wil l decrease, i .e. the actual electron affinity of the atom wil l increase, due to the larger attraction from the nucleus, and the atom "wanting" the electron more as it reaches maximum stability.

Down a group, the electron affinity decreases because of a large increase in the atomic radius, electron-electron repulsion and the shielding effect of inner electrons against the valence electrons of the atom.

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Electronegativity is a measure of the ability of an atom or molecule to attract

electrons in the context of a chemical bond. The type of bond formed is largely determined by the

difference in electronegativity between the atoms involved. Trend-wise, as one moves from left to right across

a period in the periodic table, the electronegativity increases due to the stronger attraction that the atoms obtain as the nuclear charge increases.

Moving down a group, the electronegativity decreases due to the larger distance between the nucleus and the valence electron shell, thereby decreasing the attraction, making the atom have less of an attraction for electrons or protons.

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1

2

3

4 5

6

7

• Electronegativity• Decreases going down and Increases going

right.

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• Noble gases omitted because they do not form many compounds.

• When F combines with another element, it attracts e- strongly. Tug-of-War!!

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Metall ic character refers to the chemical properties associated with elements

classified as metals. These properties, which arise from the element's ability to lose

electrons, are: the displacement of hydrogen from dilute acids; the formation of basic oxides; the formation of ionic chlorides; and their reduction reaction, as in the thermite process.

As one moves across a period from left to right in the periodic table, the metal l ic character decreases, as the atoms are more likely to gain electrons to fill their valence shell rather than to lose them to remove the shell.

Down a group, the metall ic character increases, due to the lesser attraction from the nucleus to the valence electrons (in turn due to the atomic radius), thereby allowing easier loss of the electrons or protons.

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1

2

3

4 5

6

7

• Melting/Boiling Point• Highest in the middle of a period.

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• Which atom has the larger radius?

• Be or Ba

• Ca or Br

Ba

Ca

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• Which atom has the higher 1st Ionization Energy?

• N or Bi

• Ba or Ne

N

Ne

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• Which atom has the higher melting/boiling point?

• Li or C

• Cr or Kr

C

Cr

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• Which particle has the higher electronegativity?

• K or Ca

• Al or Ga

Ca

Al

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THANK YOU FOR YOUR ATTENTION!!!

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