The Periodic Table Classifying the Elements In the periodic table: The elements are arranged in order of increasing proton number The vertical columns of elements with similar properties are called groups The horizontal rows are called periods Distinction in the table METALS NON-METALS Most of elements Fewer than metals Particular type of bonding Much wider range of properties They are divided by a line

DIFFERENCE BETWEN METALS AND NON-METALS

GROUPS AND PERIODS IN THE PERIODIC TABLE MAIN-GROUP ELEMENTS TRANSITION ELEMENTS NOBLE GASES Elements present in group I to VIII These vertical groups have similar chemical and physical properties Elements present between groups II and III The first row occurs in period 4 Elements present in group VIII The least reactive elemets Group I : alkali metals, the most reactive metals Group VII : halogens next to noble gases In centre of the table there are the most unreactive elements

GROUP I: THE ALKALI METALS They are soft solids with low melting point and low densities. They are highly reactive They have a silvery surface The physical properties change as we go down the group They react VIGOROUSLY with WATER to produce: Increases as we go down the group quickly tarnishes Became dull melting points become lower density increases HYDROGEN ALKALINE SOLUTION

GROUP VII: THE HALOGENS The most reactive non-metals Their reactivity decreses down the group They are all poisonous They all form diatomic molecules They all have a valency of 1 Their compounds with hydrogen are usually strong acids when dissolved in water Each of them produces a series of compounds with other elements They can react directly with metals to form salts They all form negative ions carrying a single charge

GROUP VIII: THE NOBLE GASES A whole group of elements remain to be discovered They are present in Earth’s atmosphere They are particulary unreactive They were refered to as the inert gases Their melting points and boiling points are extremely low The electron arrangements of atoms are very stable They are between the two most reactive groups of elements (groups I and VII) So they don’t react readily with other atoms The group VII elements gain or share electrons and the group I elements lose electrons to reach a noble gas electron arragement

What is an electron Configuration? An electron configuration is a shorthand description of how electrons are arranged around of an atom. They are important because they help us predict chemical behavior: We can predict if two elements: • will react or not • what kind of reaction we are likely to have • how strong the reaction will be

• Every element on the periodic table consists of atoms, composed of protons, neutrons and electrons (electrons exhibit a negative charge and are found around the nucleus of the atom in electron orbitals). • The four different types of orbitals (s, p, d, f) have different shapes, and one orbital can hold a maximum of two electrons. The p, d, f orbitals have different sublevels, thus can hold more electrons.

The Electron Configuration of each element is unique to its position on the periodic table. The energy level is determined by the period (from 1 to 7) and the number of electrons is given by the atomic number. Orbitals on different energy levels are similar to each other, but they occupy different areas in space. The s-block is the region of alkali metals including helium (Groups I-II) The d-block are the transition metals The p-block are the main group elements (Groups III-VIII) The f-block are the lanthanides and actinides series.