Phase 2

Newland's octave

In 1864 John Newland arranged the element in an ascending order bases on their atomic mases

Dobereid's triad

Groups of three elements could be formed that share similar properties: The first and the third element in a triad would approximately equal to the atomic mass of the second element.

Law of octaves

States that every eight element has similar properties when the elements are arranged in the increasing order of their atomic masses

Periodic table

In 1869 and 1876 Mendeleyer and Meter independently presented the peroodic table classification according to: -increasing atomic mass from left to right horizontally -elements with similar properties are placed in vertical columns -they should respond to periodic laws

Moseley's experiment

He bombarded different elements with high-enerfy electrons, he found that each element produced x-rays of a unique frequency and that it increased as the atomic mass increased

Periodic law

When the elements are placed on increasing order of their atomic number, with a periodic repetition of certain physical or chemical properties of the elements takes place

Periodicity

Lies in the configuration of their valence electrons

Current periodic table

Is due to Paneth and Werner, in it the 109 elements known so far are classified in order of increasing atomic number in eighteen columns (groups) and seven rows (periods)

Effective nuclear charge

Is the average nuclear charge felt by an individual electron in an atom Increases from left to right across any period of the periodic table

Zeff (effective nuclear charge)

Z: number of protons in a Nucleus S: inner-shell electron Zeff= Z - S

Non-bonding atomic radius

The shortest distances separating two nuclei is twice the radii of the atoms

Bonding atomic radius

Tend to increase from top to bottom and from right to left

Ion size

It depende on its nuclear charge, the number of electrons it posseses, and the orbitals in which the valence electrons reside

Cation

When it is formed, electrons are removed and they become smaller than the parent atoms

Anion

When it is formed, electrons are added, making it larger than their parent atoms

Ionization energy

Is the minimum energy required to remove an electron from the ground state of the atom or ion. Increases as we move from left to right on a period, and decreases as we move down any column

Electron affinity

The energy change that occurs when an electron is added to a gaseous atom

When ionization energy is positive..

It means that energy must be put into the atom to remove the electron •all ionization energies for atoms must be positive

When the ionization energy is negative...

It means that it is releasing energy

Metallic character

The more an element exhibits the physical and chemical properties of metals, the greater its metallic character

Metals physical properties

Ionization energy is the best indicator of whether an element behaves as a metal or a non metal -compounds made of a metal and a non metal tend to be ionic substances Most metals and metal oxides are basic

Non metals properties

Non metals tend to gain electrons when they react with metals because of their large negative electron affinity Most non metals are acidic

Metalloids

Have properties intermediate between those of metals and those of non metals Are semi conductors

Chemical bond

When two atoms or ions are strongly held together

Chemical bond types

Ionic Covalent (polar and non polar) Metallic

Lewis symbol

Consist of the element's chemical symbol plus a dot for each valence electron

Octet rule

Atoms often gain, lose or share electrons to achieve the same number of electrons as the noble gas closest to them in the periodic table

Noble gases

Have very stable electron arrangements, high ionization energies, low affinity for additional electrons and general lack of chemical reactivity. All have 8 valence electrons (except He)

Ionic substances

Results (generally) from the interactions of metals on the left side of the periodic table with nonmetallic on the right side

Ionic bonding

Electron transfer to form oppositely charged ions happen when one atom readily gives up an electron (low ionization energy) and another readily gains an electron (high electron affinity)

Covalent bonding

A chemical bond formed by sharing a pair of electrons to acquire a noble-gas electron configuration.

Multiple bonds

Atoms attack complete octets by sharing more than one pair of electrons

Bond polarity

Is a measure of how equally or unequally the electrons in a covalent bond are shared

Non polar

Is one in which the electrons are shared equally

Polar

One of the atoms exerts a greater attraction for the bonding electron than the other. If the bond polarity is large enough, an ionic bond is formed

electronegativity

Is defined as the ability of an atom in a molecule to attract electrons to itself, it is related to the atom's ionization energy

electronegativity of bonded atoms

When both electronegativities are equal it results in a non polar bond When the result of subtracting both electronegativities is less than 3, it is a polar covalent bond, and when it's greater than 3 it results in an ionic bond

Dipole moment

Whenever two electrical charges of equal magnitud but opposite sign are separated by a distance, a dipole is established measured by dipole moment in debyes (d), denoted by µ

Å to meters

10^-10m

Debyes to coulumb meters

1 d= 3.34x10^-30 C-m

Electron charge (q)

1.60x10^-19 C