Periodic Table. Periodic Law : When all elements are arranged in order of increasing atomic numbers, elements with similar chemical properties will occur are regular (periodic) intervals.
Periodic Law: When all elements are arranged in order of increasing atomic numbers, elements with similar chemical properties will occur are regular (periodic) intervals.
In modern periodic table, elements with similar chemical properties are arranged in vertical columns called groups or families.
The horizontal rows in the periodic table are called periods.
Periodic table group or family
Periodic table Period
In a modern table, elements 58-71 and 90-103 are not placed in their correct periods, but are located below the main table.
Solar system model
Niels Bohr proposed that the electron in hydrogen atom could occupy orbits only at specific distances from the nucleus. In other words, the electron moved in any one of a series of circular orbits around the nucleus.
Electron can change orbits only by absorbing or releasing energy, with higher energy orbit located farther from the nucleus.
According to the quantum mechanical model of electron behavior, the precise paths of electrons moving around the nucleus cannot be determined accurately.
Instead of circular orbits, the location and energy of electrons moving around the nucleus is specified using the three terms shell, subshell and orbital.
Locate your position on map 1
Locate your position on map 2
Locate your position on map 3
The location of electrons in a shell is indicated by assigning a number n to the shell and all electrons located in the shell.
The value of n is a whole number- 1, 2, 3, 4 etc.
The higher the n value,
Each shell is made up of one or more subshells that are designated by a letter from the group s, p, d, or f.
The number of the shell to which a subshell belongs is combined with the letter of the subshell to clearly identify subshells.
For example, a p subshell located in the third shell (n = 3) would be disignated as a 3p subshell.
The number of subshells located in a shell is the same as the number of the shell. Thus, shell number 3 (n = 3) contains three subshells, designated 3s, 3p, and 3d.
Electrons located in a subshell are often identified by using the same designation as the subshell they occupy. Thus electrons in a 3d subshell are called 3d electrons.
The description of the location and energy of an electron moving around a nucleus is completed in the quantum mechanical model by specifying an atomic orbital in which the electron is located.
Each subshell consists of one or more atomic orbitals, which are specific volumes of space around the nucleus in which electrons move.
Atomic orbitals are designated by the same number and letter used to designate the subshell to which they belong. Thus, an s orbital located in a 2s subshell would be called a 2s orbital.
All s subshells consist of a single s orbital.
All p subshells consist of three p orbitals.
All d subshells consist of five d orbitals.
All f subshells consist of seven f orbitals.
According to the quantum mechanical model, all types of atomic orbitals can contain a maximum of two electrons.
Thus, a single d orbital can contain a maximum of 2 electrons, and a d subshell that contains seven d orbitals can contain a maximum of 14 electrons.
Atomic Orbital shapes
The shape of the orbital should not be confused to mean that the electrons move around the orbital shape surface. It only determines the probability to find the electron in a specific location.
The energy of electrons around a nucleus depends on two factors.
The outermost occupied shell (with the highest n value) is called as the valence shell.
Atoms with the same number of electrons in the valence shell have similar chemical properties.
Electronic configurations give details of the arrangements of electrons in atoms.
The notation used to represent electronic configurations is 1s22s22p6 etc., where the occupied subshells are indicated by their identifying number and letter such as 2s, and the number of electrons in the subshell is indicated by the superscript on the letter. Thus, in the example above, the 2s2 notation indicates that the 2s subshell contains two electrons.
Electrons will fill subshells in the order of increasing energy of the subshells. Thus, a 1s subshell will fill before a 2s subshell.
The order of subshell filling must obey Hund's rule and the Pauli exclusion principle.
The Pauli exclusion principle-
Combined- Electrons will pair with other electrons in an orbital only if there is no empty orbital of the same energy available and if there is one electron with opposite spin already in the orbital.
Example 3.6 a, b
Some low energy subshells of a specific shell have energies lower than the upper subshell of a preceding shell.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
Electronic configuration for:
An atom that contains 17 electrons (Example 3.6)
An atom that contains 23 protons (Learning Check 3.6)
Electronic Configuration gives information about the shells, subhsells and orbitals. But are cumbersome. Hence, use
Noble Gas configuration: An electronic configuration in which the last eight electrons occupy and fill the s and p subshells of the highest-occupied shell.
Noble gas configurations can be used to write electronic configurations in an abbreviated form in which the noble gas symbol enclosed in brackets is used to represent all electrons found in the noble gas configuration.
Sodium: [Ne]3s1. The symbol [Ne] represents the electronic configuration of neon, 1s22s22p6.
An atom that contains 17 electrons
An atom that contains 23 protons
[Ne]3s2. The symbol [Ne] represents the electronic configuration of neon, 1s22s22p6.
The distinguishing electron is the last electron listed in the electronic configuration of the element.
Noble Gases: Groups VIII A filled s and p subshells (exception He)
Representative elements: s and p areas (other than VIII A)
Transition elements: d area
Inner-transition elements: f area
Metals- elements in the left two-thirds
High thermal/electrical conductivity, ductility, malleability, metallic luster.
Metalloids- elements narrow diagonal band between metals and nonmetals
Some characteristics of each
Nonmetals- elements in the right one-third
Brittle, powdery solids or gases
Ionization Energy of an element is the energy required to remove an electron from an atom of the element in the gaseous state.
This results in formation of a charged species called ion.
First ionization energy is the energy to remove the first electron from a neutral atom.
Form a group with 3 other students having different color cards
Green, Blue, Yellow, Pink
Choose an element belonging to your color
Describe the element’s properties in terms of:
Size of atom (if possible)
Representative, Transition, Inner-transition, Noble gas
Write an abbreviated electronic configuration (inner transition folks may skip this)